Abstract:
Temporarily storing audio data to be reproduced in the block form, temporarily storing synthesized audio data in the block form, generating and supplying a reference signal, and calculating the first address of the block of audio data, the editing system of the present invention enables identifying the buffering position of the recording signal and then matching the position to the reproduced signal, resulting in quick editing.

Description:
This is a Continuation of application Ser. No. 09/285,339 filed Apr. 2, 1999 now U.S. Pat. No. 6,356,701. 

   BACKGROUND OF THE INVENTION 
   1. Field of the Invention 
   This invention relates to an editing system and method and a distribution medium and more particularly to an editing system and method and a distribution medium which are capable of quick editing. 
   2. Description of the Related Art 
   In recent years, various computer systems have been developed rapidly, consumers have become eager to require enhanced external memory with the development of computer systems. The device that had developed in response to the request is a disk array unit. A disk array unit has a plurality of built-in disk devices therein to enlarge the capacity, in which disk array unit disk devices are operated in parallel to speed up reading operation and writing operation and error correction data is involved to improve the reliability. 
   When the data is stored in a disk array unit, the data is divided into a plurality of subblocks, error correction data is generated for each subblock, all the subblocks and error correction data are written in separate disk devices respectively. 
   On the other hand, when the data is read out from a disk array unit, a plurality of subblocks and error correction data are read out simultaneously from disk devices in which subblocks and error correction data, components of the data, are stored, the original data is re-structured from the read out subblocks, and the data is sent out as it is if no error is contained. When, if any subblock can not be read out normally because of damage of a recording area where the subblock is stored, the correct data is restored using other subblocks which are read out normally and error correction data and the restored data is sent out. 
   In the case of a disk array unit, even if one disk device is damaged completely, it is possible to restore the data by a procedure in which the damaged disk device is replaced with a new disk device and the data in other disk devices are used. 
   Some different types of disk array unit which involves error correction data have been known. Professor David A Patterson, UC Barclay School, classified the type into 5 classes, and proposed a new term namely level of RAID (Redundant Arrays of Inexpensive Disks). Summary of this proposal is described herein under. 
   RAID-1 is the class which doubles the data of a disk device, and alternatively called as mirrored disk. In a RAID-1, the quite same data are stored in two disk devices. In a RAID-2 or 3, the input data is divided in bit unit or byte unit, and divided data are stored in a plurality of disk devices. Hamming code is used in RAID-2, and parity is used in RAID-3 respectively as the error correction data. In a RAID-4 or RAID-5, the data is interleaved in sector unit. In a RAID-4, parity is stored in one disk device, on the other hand, in a RAID-5, parity is stored in a plurality of disk devices dispersedly. 
   RAID-3 and RAID-5 are used most popularly for the general disk array unit out of these RAID levels.  FIG. 82  show an exemplary structure of a RAID-3 type disk array unit, and  FIG. 83  shows an exemplary structure of a RAID-5 type disk array unit. 
   In the RAID-3 type disk array unit shown in  FIG. 82 , the input data is divided in byte unit, and the data divided in byte unit are stored in a plurality of disk devices. The parity is stored in a pre-determined disk device as the error correction data. Herein, parities P 1 - 4  corresponding to the data having the number 1 to 4 stored in a plurality of disk devices and parities P 5 - 8  corresponding to the data having the number 5 to 8 are stored. 
   In the RAID-5 type disk array unit shown in  FIG. 83 , the input data is divided in sector unit, these data are interleaved and stored in a plurality of disk devices dispersedly. In this case, data A, E, and I are stored in the first disk device, data B, F, and J are stored in the next disk device, data C, G, and parities PI-L corresponding to data I to L are stored in the next disk device. Data D, K, and parities PE-H corresponding to data E to H are stored in the next disk device, and parities PA-D corresponding to data A to D and data H and L are stored in the last disk device. 
   Recent development of computer system provides computers with the function to involve images and sound which are typical of multimedia data, a storage for these multimedia is some times referred as multimedia server. Because a large capacity and high transfer rate are required for a multimedia server, it is mostly realized in the form of disk array unit as a hardware system. An emphasis is placed on average processing performance for conventional computer server, on the other hand, an emphasis is placed on suppression of the worst value of the time required to complete processing for multimedia server. 
   For example, in the case of dynamic image, the motion is step-wise unless 30 images are displayed sequentially with a certain interval per second. The capacity of a disk device is insufficient for the motion, and if audio data becomes insufficient, then sound is interrupted and harsh noise is generated. Guaranty of upper limit time that processing is completed within the time at worst case is referred as guaranty of real-time. The guaranty of real-time is important for the multimedia server. 
   However, in the device explained above, video data and audio data cannot be processed quickly in real time and considerable time is required for editing even if the above device is used for the editing system, and so quick editing is impossible. 
   Moreover, when an audio signal is reproduced from the device explained above and a part thereof is updated in synchronism with the reproduced signal, it has been difficult to identify the buffering position of the recording signal and then match the position to the reproduced signal because the reproduced signal (old data) and recording signal (new data) are temporarily recorded respectively to independent buffers and the recording signal is delayed from the reproduced signal. 
   Moreover, the device explained above also has a problem that it is difficult to synthesize and record a plurality of reproduced signals in their arbitrary combinations. 
   Further, when video and audio signals are reproduced simultaneously at arbitrary positions on the above-mentioned device, a deviation of audio signal reproduction occurs due to the difference between the video frame frequency and the audio sampling frequency. 
   SUMMARY OF THE INVENTION 
   The present invention has been proposed considering such background and therefore it can identify the buffering position of the recording signal and then match the position to the reproduced signal. 
   According to the present invention of the editing system, temporarily storing audio data to be reproduced in the block form, temporarily storing synthesized audio data in the block form, generating and supplying a reference signal, and calculating the first address of the block of audio data enable identifying the buffering position of the recording signal and then matching the position to the reproduced signal. 
   Further, according to the present invention of the editing system, generating a reference signal, calculating the first address of the block of recording signals, and distributing and synthesizing arbitrary audio data enable recording of arbitrary combinations in arbitrary locations. 
   Moreover, according to the present invention of the editing system, generating a reference signal, calculating the first address of the block of recording signals, and detecting the first phase of the block of the recording signals enable preventing the deviation of audio signals from video signals. 
   According to the present invention, an editing system comprises reproducing means for reproducing original audio data recorded in randomly accessible recording media and outputting the reproduced audio data through reproduction buffers; recording means for recording insert audio data supplied from the outside in the recording media through recording buffers; and control means for controlling the reproducing means and the recording means so that the insert audio data is recorded in a location where the original audio data is recorded and for determining storing addresses of the recording buffers for buffering the insert audio data based on the difference between the addresses of said reproduction buffers and the addresses of said recording buffers at the identical time. 
   According to the present invention, an editing method comprises a first storing step of temporarily storing audio data to be reproduced in the block form; a receiving step of receiving the input of audio data to be synthesized; a synthesizing step of synthesizing the reproduced audio data and the audio data received in the receiving step; a second storing step of temporarily storing the audio data synthesized in the synthesizing step in the block form; a reference signal generating step of generating a reference signal to supply the reference signal in the first and second storing steps; and an calculating step of calculating the first address of the block of the audio data stored in the second storing step. 
   According to the present invention, a distribution medium for providing a program which controls an editing system to perform a process comprises a first storing step for temporarily storing the audio data to be reproduced in the block form; a receiving step of receiving the input of audio data to be synthesized; a synthesizing step of synthesizing the reproduced audio data and the audio data received in the receiving step; a second storing step of temporarily storing the audio data synthesized in the synthesizing step in the block form; a reference signal generating step of generating a reference signal to supply the reference signal in the first and second storing steps; and an calculating step of calculating the first address of the block of the audio data stored in the second storing step. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
       FIG. 1  is a block diagram for illustrating an exemplary structure of an editing system to which the present invention is applied. 
       FIG. 2  is a block diagram for illustrating the structure of the editing system shown in  FIG. 1 . 
       FIG. 3  is a block diagram for illustrating the structure of the system control section shown in  FIG. 2 . 
       FIG. 4  is a block diagram for illustrating the structure of the matrix switcher section shown in  FIG. 2 . 
       FIG. 5  is a block diagram for illustrating the structure of the video processing section shown in  FIG. 2 . 
       FIG. 6  is a block diagram for illustrating the structure of the audio processing section shown in  FIG. 2 . 
       FIG. 7  is a block diagram for illustrating an exemplary structure of the disk recorder shown in  FIG. 1 . 
       FIG. 8  is a block diagram for illustrating an exemplary structure of the CPU block shown in  FIG. 7 . 
       FIG. 9  is a diagram for illustrating an example of ZBR table shown in  FIG. 8  in the case of NTSC. 
       FIG. 10  is a diagram for illustrating an example of ZBR table shown in  FIG. 8  in the case of PAL. 
       FIGS. 11A and 11B  are diagrams for describing the relation between cylinder, track, and sector. 
       FIG. 12  is a diagram for describing the recording principle of ZBR. 
       FIGS. 13A and 13B  are diagrams for describing an example of the block map shown in  FIG. 8 . 
       FIG. 14  is a diagram for describing the format of the block map shown in  FIG. 8 . 
       FIG. 15  is a diagram for describing an example of the block map shown in  FIG. 8 . 
       FIG. 16  is a flow chart for describing the process for forming a block map. 
       FIG. 17  is a graph for describing the characteristics of the seek time. 
       FIG. 18  is a diagram for describing the gap θgap. 
       FIG. 19  is a diagram for describing the gap θgap and skew θskew. 
       FIG. 20  is a diagram for describing the skew between a plurality of cylinders. 
       FIG. 21  is a graph for describing the relation between the gap θgap and the cylinder. 
       FIG. 22  is a graph for describing the relation between the gap θgap and the cylinder. 
       FIG. 23  is a graph for describing the relation between the gap θgap and the cylinder. 
       FIG. 24  is a diagram for describing the scheduling. 
       FIG. 25  is a diagram for describing the overhead. 
       FIG. 26  is a flow chart for describing the scheduling processing of the controller shown in  FIG. 7 . 
       FIG. 27  is a flow chart for describing the arrangement processing of the k-th data of the controller shown in  FIG. 7 . 
       FIG. 28  is a flow chart for describing the detailed processing of the step S 31  shown in  FIG. 27 . 
       FIG. 29  is a flow chart for describing the detailed processing of the step S 32  shown in  FIG. 27 . 
       FIG. 30  is a flow chart for describing the detailed processing of the step S 51  shown in  FIG. 29 . 
       FIG. 31  is a flow chart for describing the detailed processing of the step S 52  shown in  FIG. 29 . 
       FIG. 32  is a flow chart for describing the detailed processing of the step S 33  shown in  FIG. 27 . 
       FIG. 33  is a diagram for describing the data arrangement on a hard disk realized by the processing shown in  FIG. 28 . 
       FIGS. 34A and 34B  are diagrams for describing generation of the parity data. 
       FIGS. 35A and 35B  are diagrams for describing error correction using the parity data. 
       FIG. 36  is a block diagram for illustrating bit conversion processing of the RAID controller shown in FIG.  36 . 
       FIGS. 37A and 37B  are diagrams for describing bit conversion processing of the RAID controller shown in  FIG. 36 . 
       FIG. 38  is a diagram for describing operation of the FIFO shown in  FIG. 36 . 
       FIG. 39  is a diagram for describing the pixel data of 1 frame image. 
       FIG. 40  is a diagram for describing the packet transfer block. 
       FIG. 41  is a diagram for describing the DMA command. 
       FIG. 42  is a diagram for describing data writing in the data buffer shown in  FIG. 36 . 
       FIG. 43  is a diagram for describing the RAID area of 1 frame image. 
       FIG. 44  is a diagram for describing the structure of subblocks of 1 frame image shown in  FIG. 43 . 
       FIG. 45  is a diagram for describing the DMA command for reproduction in the case of no error. 
       FIG. 46  is a diagram for describing the DMA command for reproduction in the case of error. 
       FIG. 47  is a block diagram for illustrating the detailed structure of the RAID controller shown in  FIG. 36 . 
       FIG. 48  is a diagram for describing parity generation processing in the RAID controller shown in  FIG. 47 . 
       FIG. 49  is a diagram for describing data correction processing in the RAID controller shown in  FIG. 47 . 
       FIG. 50  is a diagram for describing an exemplary structure of the parity data and subblock of NTSC. 
       FIG. 51  is a diagram for describing an exemplary structure of the parity data and subblock of NTSC. 
       FIG. 52  is a diagram for describing an exemplary structure of the parity data and subblock of NTSC. 
       FIG. 53  is a diagram for describing an exemplary structure of the parity data and subblock of NTSC. 
       FIG. 54  is a diagram for describing an exemplary structure of the parity data and subblock of NTSC. 
       FIG. 55  is a diagram for describing an exemplary structure of the parity data and subblock of NTSC. 
       FIG. 56  is a diagram for describing an exemplary structure of the parity data and subblock of PAL. 
       FIG. 57  is a diagram for describing an exemplary structure of the parity data and subblock of PAL. 
       FIG. 58  is a diagram for describing an exemplary structure of the parity data and subblock of PAL. 
       FIG. 59  is a diagram for describing an exemplary structure of the parity data and subblock of PAL. 
       FIG. 60  is a diagram for describing an exemplary structure of the parity data and subblock of PAL. 
       FIG. 61  is a diagram for describing an exemplary structure of the parity data and subblock of PAL. 
       FIG. 62  is a diagram for describing arrangement of the subblock data of each frame on each disk. 
       FIG. 63  is a diagram for describing the structure of the stream. 
       FIG. 64  is block diagram for illustrating an exemplary detailed structure of the audio block  231  shown in  FIG. 7 . 
       FIGS. 65A to 65C  are diagrams for describing insert processing of audio. 
       FIG. 66  is a block diagram for illustrating processing performed by the audio block  231  shown in  FIG. 64 . 
       FIG. 67  is a diagram for describing processing performed by the cross fader  607  shown in  FIG. 66 . 
       FIG. 68  is a diagram for describing processing performed by the cross fader  607  shown in  FIG. 66 . 
       FIG. 69  is a flow chart for describing head address calculation processing performed by the recording block. 
       FIG. 70  is a diagram for describing head address calculation processing performed by the recording block. 
       FIG. 71  is a block diagram for illustrating processing performed by the audio block  231  shown in  FIG. 64 . 
       FIG. 72  is a block diagram for illustrating processing performed by the audio block  231  shown in  FIG. 64 . 
       FIG. 73  is a diagram for describing an example of the signal which the multi-cross fader  622  shown in  FIG. 72  synthesizes. 
       FIG. 74  is a diagram for describing the phase of the audio signal. 
       FIGS. 75A to 75C  are diagrams for describing processing performed by the variable speed reproduction processor  510  shown in  FIG. 64 . 
       FIG. 76  is a block diagram for illustrating the detailed structure of the variable speed reproduction processor  510  shown in  FIG. 64 . 
       FIG. 77  is a block diagram for illustrating the detailed structure of the pitch extraction section shown in  FIG. 76 . 
       FIG. 78  is a graph for describing the source sound data string. 
       FIGS. 79A to 79F  are diagrams for describing processing performed by the audio concatenation processor  704 . 
       FIG. 80  is a diagram for describing the built-in calculation circuit in the audio concatenation processor  704 . 
       FIGS. 81A to 81F  are diagrams for describing processing performed by the audio concatenation processor  704 . 
       FIG. 82  is a diagram for describing the conventional RAID. 
       FIG. 83  is a diagram for describing the conventional RAID. 
   

   DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
   Embodiments of the present invention will be described in detail hereinafter, before the description of embodiments, features of the present invention are described with adding corresponding embodiments (only one example) in the parenthesis after the description of each means in order to clarify the correlative relation between each means of the invention described in the scope of claims for patent and the embodiment described hereinafter. 
   The editing system of the present invention comprises a first storing means (for example, hard disks  201 - 1  to  201 - 28  in  FIG. 7 ) for storing video data, a second storing means (for example; hard disks  201 - 29  to  201 - 32  in  FIG. 7 ) for storing audio data; and control means (for example, controller  262  in  FIG. 7 ) for controlling the first storing means based on the RAID-5 method and FARAD algorithm and the second storing means based on the RAID-1 method. 
     FIG. 1  shows an exemplary structure of an editing system to which the present invention is applied. In this system, the video data is supplied from a source video tape recorder (VTR)  9  and a daily server  7  to an editing system  1 , and the video data is subjected to editing. The editing system  1  controls a disk recorder  2  to perform editing. The editing system  1  transmits the video data and audio data to the disk recorder  2  through a two channel SDI (Serial Data Interface), and the disk recorder  2  supplies 6 channel video data and 16 channel audio data to the editing system  1  though the SDI. Further, the editing system  1  supplies the audio data and video data to a main monitor  4 , an on air buffer  8 , the source VTR  9 , a host personal computer  3  through the SDI. Further, the editing system  1  supplies the audio signal to an amplifier  5  to generate sound from a speaker  6 . 
   On the other hand, the host personal computer  3  supplies a command to the editing system  1  through RS 422 to control it. Further, the editing system  1  sends a command to the disk recorder  2 , daily server  7 , and source VTR  9  through the RS 422 to control them. Further, the editing system  1  is controlled by Ethernet through the host personal computer  3 , and controls external apparatuses. The disk recorder  2  is controlled by the host personal computer  3  through the SCSI (ANSI, Small Computer System Interface). 
     FIG. 2  shows an exemplary internal structure of the editing system  1 . The editing system  1  comprises a matrix switcher section  21  a video processing unit  22 , an audio processing unit  23 , and a system control section  24  connected each other through a control bus  25 . 
   As shown in  FIG. 3 , the system control section  24  is provided with a main CPU  121  for controlling the matrix switcher section  21 , the video processing section  22 , and the audio processing unit  23  through a control bus  25 , and provided with a device control CPU&#39;s  122 - 1  to  122 - 3  for controlling devices such as the source VTR  9 , the disk recorder  2  served as a local storage, and daily server  7  through the control bus  25 . Further, the system control section  24  is provided with a communication CPU  124  for operating interface processing for GUI and for operating input and output transmission of the reference time record between the host personal computer  3 . 
   As shown in  FIG. 4 , the matrix switcher section  21  is a block for switching the input line and output line. The matrix switcher section  21  is provided with  12  input lines  31 - 1  to  31 - 12  for receiving the video signal or audio signal supplied based on the SDI format. 12 output lines corresponding to 12 input lines are disposed in the form of matrix, each output line is provided with output processors  32 - 1  to  32 - 12 . Input lines  31 - 1  to  31 - 12  and  12  output lines corresponding to the output processors  32 - 1  to  32 - 12  are connected at cross points marked with X as required. The control block  34  of the matrix switcher section  21  receives a command from the main CPU  121  of the system control section  24  through the control bus  25 , and the connection is controlled correspondingly to the command. 
   Not only the video signal and audio signal from the daily server  7 , the source VTR  9 , or the disk recorder  2  shown in  FIG. 1  is supplied to this input line but also the video signal processed by the video processing section  22  is supplied to this input line. The control block  34  supplies these prescribed inputs to any one of output processors  32 - 1  to  32 - 12  of the  12  output lines by switching the cross point as required. The output processors  32 - 1  to  32 - 12  convert the input video signal to the signal of SDI format. The output of the output processor  32 - 1  is changed to a capture line output, and supplied to the host personal computer  3 . The output of the output processor  32 - 2  is served as the output of the preview line, and supplied to the main monitor  4 . 
   On the other hand, on the rear end of the output processors  32 - 3  to  32 - 12 , combiners  33 - 1  to  33 - 10  are provided, these combiners  33 - 1  to  33 - 10  superimpose embedded audio signal supplied from the audio processing unit  23  on the SDI video signal supplied from corresponding output processors  32 - 3  to  32 - 12 . Output of the combiners  33 - 1  to  33 - 10  is supplied as the output of program outline to the disk recorder  2  which is served as a local storage. Herein, the embedded audio signal means the superimposed audio signal which is subjected to time base compression in the horizontal blanking period of the video signal. 
   As shown in  FIG. 5 , the video processing unit  22  is a block for operating image conversion processing of the video signal supplied from the matrix switcher section  21 . The image conversion processing includes, for example, processing for applying special effect on the source video signal, animation effect processing for inserting the video signal which is formed by applying special effect to the background video signal, and transition effect processing for switching the image from the background video signal to foreground video signal. 
   The video processing section  22  comprises a demultiplexer block  41  for extracting the key signal or video signal (luminance signal and chroma signal) from the SDI format signal which is supplied from the matrix switcher section  21 , a switcher block  42  for producing the transition effect such as wipe on the key signal or video signal, a special effect block  43  for producing animation effect such as three-dimensional image conversion on the key signal or video signal, a mixer block  44  for mixing the video signal from the switcher block  42 , the special effect block  43 , and the matrix switcher section  21 , and a control block  45  for controlling the demultiplexer block  41 , the switcher block  42 , the special effect block  43 , and the mixer block  44 . 
   The control block  45  receives a control signal from the system control section  24  through the control bus  25 , and controls the demultiplexer block  41 , the switcher block  42 , the special effect block  43 , or the mixer block  44  through a control line not shown in the drawing. 
   The demultiplexer block  41  is provided with demultiplexer circuits  41 - 1  to  41 - 5 , these demultiplexer circuits  41 - 1  to  41 - 5  are circuits for extracting a packet video signal so that the format is equivalent to SDI format supplied from the matrix switcher section  21 , and extract a video signal recorded in the area of the pay load part of each packet data based on the sync signal and header information recorded on the head of each video signal recorded serially. 
   The switcher block  42  is provided with wipe signal generating circuits  52 - 1  and  52 - 2  for generating a wipe signal corresponding to the transition effect indicated by an operator in response to a control command from the control block  45 . The wipe signal generating circuit  52 - 1  supplies a generated wipe signal to a key signal processing circuit  51 - 1  and a video signal processing circuit  51 - 2 , and the wipe signal generating circuit  52 - 2  supplies a generated wipe signal to a key signal processing circuit  51 - 3  and a video signal processing circuit  51 - 4 . 
   The key signal processing circuit  51 - 1  processes a key signal supplied from the demultiplexer circuit  41 - 1  correspondingly to a wipe signal supplied from the wipe signal generating circuit  52 - 1 , and generates a new key signal. The video signal processing circuit  51 - 2  processes a video signal supplied from the demultiplexer circuit  41 - 2  correspondingly to a wipe signal supplied from the wipe signal generating circuit  52 - 1 . 
   Similarly, the key signal processing circuit  513  processes a key signal supplied from the demultiplexer circuit  41 - 3  correspondingly to a wipe signal supplied from the wipe signal generating circuit  52 - 2 , and generates a new key signal. The video signal processing circuit  51 - 4  processes a video signal supplied from the demultiplexer circuit  41 - 4  correspondingly to a wipe signal supplied from the wipe signal generating circuit  52 - 2 . 
   In the special effect block  43 , a key signal or video signal supplied respectively from the key signal processing circuit  51 - 3  or the video signal processing circuit  51 - 4  is stored in a frame memory  61 - 1  or a frame memory  61 - 2 . A three-dimensional address generation circuit  63  receives a special image conversion control command from the control block  45 , generates a conversion address for converting a key signal or video signal respectively to a three-dimensional image, and delivers it to the frame memories  61 - 1  and  61 - 2  and interpolators  62 - 1  and  62 - 2 . In the frame memories  61 - 1  and  61 - 2 , reading out of a key signal or video signal is controlled correspondingly to a conversion address from the three-dimensional address generation circuit  63 . The interpolators  62 - 1  and  62 - 2  operate processing for spatially interpolating the pixel of a key signal or video signal supplied respectively from the frame memory  61 - 1  or the frame memory  61 - 2  based on a conversion address from the three-dimensional address generating circuit  63 . 
   In the mixer block  44 , a mix circuit  71 - 1  combines a transformed video signal supplied from the interpolator  62 - 2  and a background video signal supplied from the demultiplexer circuit  41 - 5  based on an image-transformed key signal supplied from the interpolator  62 - 1 . A mix circuit  71 - 2  combines a video signal supplied from the mix circuit  71 - 1  and a video signal processed based on a wipe signal in the video signal processing circuit  51 - 2  correspondingly to a key signal processed based on a wipe signal supplied from the key signal processing circuit  51 - 1 . The video signal delivered from the mix circuits  71 - 1  and  71 - 2  is supplied to two input lines out of 12 input lines of the matrix switcher section  21 . 
   As shown in  FIG. 6 , in the audio processing unit  23 , a separator block  81  is provided with separators  81 - 1  to  81 - 3 , and these separators  81 - 1  to  81 - 3  separate an embedded audio signal from an SDI format signal supplied from the matrix switcher section  21 . These signals are AES/EBU (Audio Engineering Society/European Broadcasting Union) format signal. 
   A mixer block  83  is provided with an adder  92 - 1  which adds the output of the separators  81 - 1  to  81 - 3  after the output is adjusted to a prescribed level by variable resistors  92 - 1  to  92 - 3 , and provided with an adder  92 - 2  which adds the output of the separators  81 - 1  to  81 - 3  after the output is adjusted to a prescribed level by variable resistors  91 - 4  to  91 - 6 . 
   An embedded circuit  85  converts an audio signal delivered from the adders  92 - 1  and  92 - 2  to an embedded audio signal so that the audio signal is to be superimposed on an SDI format signal. The output of the embedded circuit  85  is supplied to the combiners  33 - 1  to  33 - 10  of the matrix switcher section  21 , and superimposed on a video signal which has been converted to an SDI format signal by the output processors  32 - 3  to  32 - 12 , and then supplied to the disk recorder  2 . 
   A control block  86  controls operation of the separator block  81 , the mixer block  83 , and the embedded circuit  85  based on a control signal which is received from the system control section  24  through the control bus  25 . 
   The output of the adders  92 - 1  and  92 - 2  comes out from a speaker  6  through the amplifier  5  shown in  FIG. 1 . 
     FIG. 7  shows an exemplary internal structure of the disk recorder  2 . The disk recorder  2  is a type of disk recorder to which hard disk management algorithm FARAD (Fat Random Access Disk) (bland name) is applied for fast real time random access, and allows fast random access to multi-channel data with a disk having a relatively small capacity. 
   In this exemplary structure,  32  hard disks  201 - 1  to  201 - 32  are provided, hard disks  201 - 1  to  201 - 28  out of these hard disks are served for video signal recording of RAID-5 system, on the other hand, hard disks  201 - 29  to  201 - 32  are served for audio signal recording of RAID-1 system. SCSI controllers  202 - 1  to  202 - 16  served as SPCs (SCSI Peripheral Controller) respectively control two hard disks. For example, the SCSI controller  201 - 1  controls the hard disk  201 - 1  and hard disk  201 - 2 , SCSI controller  201 - 2  controls the hard disk  201 - 3  and hard disk  201 - 4 . 
   Further, buffer blocks  203 - 1  to  203 - 8  are provided. One buffer block controls two SCSI controllers, for example, the buffer block  203 - 1  controls the SCSI controller  202 - 1  and SCSI controller  202 - 2 , and the buffer block  203 - 2  controls SCSI controller  202 - 3  and SCSI controller  202 - 4 . Each buffer block  203 -i (i is an arbitrary value, and herein i=1, 2, . . . 8) is provided with a data buffer  212 -i and a buffer controller  211 -i which is served for controlling the data buffer  212 -i. 
   Further, a serial address which is specified definitely by a controller  262  of a CPU block  261  is allocated to the data buffers  212 - 1  to  212 - 8 , and the memory position of data is indicated based on the address. Therefore the controller  262  regards the plurality of data buffers  212 - 1  to  212 - 8  as one data buffer. 
   This disk recorder  2  can have totally  36  hard disks, but in this exemplary structure,  32  hard disks are provided. 
   As a block for recording/reproducing audio data, an audio block  231  is provided to these hard disks  201 - 29  to  201 - 32 , and video blocks  271 - 1  to  271 - 6  are provided to the hard disks  201 - 1  to  201 - 28  for recording/reproducing video data. 
   The audio block  231  processes audio data for  16  channels. The audio block  231  is provided with an input-output (I/O) controller  242  and a DMA controller  241 . The input-output controller  242  receives supply of an audio signal for  16  channels from any one of the combiners  33 - 1  to  33 - 10  of the matrix switcher unit  21  shown in  FIG. 4 , processes the audio signal, supplies it to the DMA controller  241 , as well as processes an audio signal for the maximum  18  channels supplied from the DMA controller  241 , and delivers it to the input line of the matrix switcher section  21  of the editing system  1  shown in  FIG. 4 . 
   The DMA controller  241  supplies an audio signal supplied from the input-output controller  242  to the buffer controller  211 - 8  through a DMA bus  251  for DMA transfer to the corresponding data buffer  212 - 8 . Further, the DMA controller  241  reads the data read out from the data buffer  212 - 8  through the DMA bus  251 , and DMA-transfers to the input-output controller  242 . 
   In the video block  271 -i (i=1, 2, . . . , 6), a DMA controller  281 -i DMA-transfers the video data between the data buffers  212 - 1  to  212 - 7  and RAID controller  282 -i through the DMA bus  251 . 
   The RAID controller  282 -i processes the video data to be recorded in the hard disks  201 - 1  to  201 - 28  supplied from a video processing section  283 -i for error correction and supplies it to the DMA controller  281 -i, and processes the data reproduced from the hard disks  201 - 1  to  201 - 28  supplied from the DMA controller  281 -i for error correction, and then delivers it to the video processing section  283 -i. Detailed processing of the RAID controller  282 -i will be described hereinafter. 
   The video processing section  283 -i operates processing for converting the video data supplied from an input output controller  284 -i to a clock rate required to process on the RAID controller  282 -i side, and in the opposite direction, operates processing for converting the reproduction data supplied from the RAID controller  282 -i to a clock rate to be processed by the input-output controller  284 -i. 
   The input-output controller  284 -i receives the video data supplied from any one of combiner  33 - 1  to  33 - 10  of the matrix switcher section  21  of the editing system  1  and supplies it to any one of the video processing sections  283 - 1  to  283 - 6  with switching, and in the opposite direction, supplies the video data supplied from the video processing section  283 -i to the input line of the editing system  1 . 
   Because this exemplary structure is provided  6  video blocks  271 - 1  to  271 - 6 , it is possible to process totally the video signal of 6 channels. 
   The CPU block  261  is provided with the controller  262  and a RAM  263  and connected to the SCSI controller  202 -i, the buffer block  203 -i, the DMA controller  241 , the input-output controller  242 , the DMA controller  281 -i, the RAID controller  282 -i, the video processing section  283 -i, and input output controller  284 -i, and controls these components as required. The controller  262  controls blocks and the RAM  263  stores software programs and table data which are required for the controller  262  to operate various processing. The controller  262  generates and updates the determined format parameter and generates and updates a block map  304  based on the data from a zone bit recording (ZBR) table  301  formed in the RAM  263  as shown in  FIG. 8 . Herein, the format parameter comprises the size of one block of data S, the number of division of data n, and the optimal skew value θskew. 
   The controller  262  generates a command for controlling operation of the DMA controller  281 -i and RAID controller  282 -i with reference to the block map  304 . Further, the controller  262 , when video data or audio data which is buffered to the data buffer  212 -i is recorded or reproduced to or from the hard disk  201 -i, performs processing for scheduling the access order of the head so that the head migration is minimized. 
   Additionally, the controller  262  generates and records a physical address table  302  and allocation map  303  in the RAM  263  as shown in  FIG. 8 . 
   The zone bit recording (ZBR) table  301  is a table in which the cylinder address of the hard disk is correlated to the number of sectors used in one track at the cylinder position.  FIG. 9  and  FIG. 10  show examples of the ZBR table,  FIG. 9  shows an example of ZBR table involving the video signal of NTSC standard, and  FIG. 10  shows an example of ZBR table involving the video signal of PAL standard. 
   As shown in  FIGS. 11A and 11B , the hard disk  201 -i comprises a plurality of media (disks), and a plurality of tracks are formed on each medium. Each track is segmented into a plurality of sectors, and each sector is a size of 512 bytes. An area comprising tracks positioned at the same radius distance from the center of each medium is referred as cylinder. Successive numbers are assigned to the cylinder from the outer side to inner side in the order, and these numbers are referred as cylinder address. 
   Each hard disk  201 -i is formatted by way of zone bit recording. In detail, the recording surface is segmented into a plurality of zones correspondingly to the distance from the center of a disk and formatted so that the number of sectors per track is larger for the outer zone than for inner zone. In the case of this embodiment, as shown in  FIG. 9 ,  FIG. 10 , and  FIG. 12 , 6000 tracks specified by cylinder addresses 0001 to 6000 are formed from the outermost circumference to the innermost circumference, and segmented into 12 zones, each zone contains 500 tracks. As shown in  FIG. 9 , for example, in the first zone on the outermost side specified by the cylinder addresses 0001 to 0500, 567 sectors are formed per one track, on the other hand, in the 12th zone on the innermost side specified by the cylinder addresses 5501 to 6000, 393 sectors are formed per one track. 
   Though details will be described hereinafter, out of these 12 zones, the first zone on the outermost circumference and the second zone on the innermost circumference are used combinedly as a pair, and similarly in the following, the second zone and the 11th zone, the third zone and the 10th zone, the fourth zone and ninth zone, the fifth zone and eighth zone, and the sixth zone and seventh zone, are respectively used combinedly as a pair. The combined use of an outer circumferential zone and an inner circumferential zone as a pair allows most efficient use of the disk capacity. This point will be described in detail hereinafter. 
   Because the number of sectors per track for the respective zones is stored in the ZBR table  301 , when a cylinder address is specified, then the number of sectors available on the track is determined. In this embodiment,  128  words data ( 1  word corresponds to 32 bits) are recorded in one sector. 
   On the other hand, the physical address table  302  shown in  FIG. 8  is a table for correlating the logical sector number of the hard disk  201 -i (this logical sector number is alternatively referred as logical block address) to the physical address. The physical address is referred as the address comprising the cylinder number, the medium number, and the sector number. 
     FIGS. 13A and 13B  show an example of the physical address table  302 . The logical sector number Lki is the number assigned sequentially to each sector of all the media in each hard disk  201 -i, and as shown in  FIG. 13A , the logical sector number Lki is specified by the cylinder number CYLki, the medium number MEDki, and the sector number SECki.  FIG. 13B  shows a detailed example. For example, a sector corresponding to the logical sector number of 2 is the sector at the position of cylinder number  0 , medium number  0 , and sector number  2 . Therefore, the logical sector number is converted to the physical sector number, or conversely, the physical sector number is converted to the logical sector number with reference to the physical address table  302 . 
   The allocation map  303  shown in  FIG. 8  is a map for managing the address of recorded areas and un-recorded areas of all the media (disks) of the hard disk  201 -i. Un-recorded areas of each disk is searched with reference to the allocation map  303 . 
   The block map  304  is a map on the table for indicating the size of stored data, and a map for managing the map location on a disk for each block data (data to be recorded or data to be reproduced) having a block number indicated with k (an arbitrary natural number not exceeding the total number of the data) as shown in  FIG. 14 . One block data indicated with the block number k is, for example, the video data of one frame (an image having a prescribed size), and the block number k is the number (ID number) specified correspondingly to each frame data of the video data of all the channels. When a reproduction of a video data is requested, the map location on a disk can be specified with reference to the block number k. 
   As shown in  FIG. 15 , the block data for one frame comprises n subblock data and one error correction parity data, these data are recorded in different hard disks  201 -i respectively. The map location of the parity data is specified by the disk IDDkp of the hard disk  201 -i, the logical sector number Lkp which indicates recording start position on the area where the parity data is recorded, and the number of sectors Skp which indicates the size of the area where the parity data is recorded. 
   Similarly, the map location of the subblock having the number of k is specified by the disk IDDki of the hard disk  201 -i, the logical sector number Lki which indicates the recording start position of the area where the subblock is recorded, and the number of sectors Ski which indicates the size of the area where the subblock is recorded. 
   Herein, n (number of divided video data formed from  1  frame video data) is prescribed as desired depending on the standard (NTSC or PAL) (quantity of data). Details will be described hereinafter. 
     FIG. 15  shows a detailed example of a block map  304  in which NTSC 1 frame video data comprising 1440×512 pixels is divided into 4 subblocks. In this example, the parity data P 1  of the frame indicated with the block number (frame number) 1 is recorded from the start logical sector of number 0 on the hard disk indicated with the disk ID of 1 over an area of 567 sectors (outermost circumferential area). The data S 1 - 1  of the first subblock of the frame indicated with the block number  1  is recorded from the start logical sector of 599600 on the hard disk indicated with the disk ID 2 over an area of 393 sectors (innermost circumferential area), similarly in the following, the data S 1 - 2  of the second subblock of this frame is recorded from the start logical sector of the number 0 on the hard disk indicated with the disk ID 3 over an area of 567 sectors (outermost circumferential area), the data S 1 - 3  of the third subblock is recorded from the start logical sector of the number 599600 on the hard disk indicated with the disk ID 4 over an area of 393 sectors (innermost circumferential area), and the data S 1 - 4  of the fourth subblock is recorded from the start logical sector of the number 0 on the hard disk indicated with the disk ID 5 over an area of 567 sectors (innermost circumferential area). 
   The size of data for 1 subblock is basically ¼ of 1 frame data, however, 1 subblock data is not always the data constituted with successive ¼ pixel data of 1 frame video data. Of course, it is possible to constitute the pixel data of 1 subblock data with the pixel data of successive ¼ area of 1 frame video data, however, in such case, the impact which likely occurs when the pixel data is missed will be the larger. To avoid such problem, a plurality of packet transfer blocks comprising the pixel data on the prescribed area located dispersedly is collected out of 1 frame video data instead of successive areas to constitute 1 subblock. The size of each subblock is not always equal. This point will be described in detail hereinafter with reference to  FIG. 43  and  FIG. 44 . 
   Next, processing for forming the block map  304  which is operated by the controller  262  of the CPU block  261  is described with reference to a flow chart shown in  FIG. 16 . In the following description, for example, in the case that hard disks  201 - 1  to  201 - 32  are not necessarily described discriminately, these hard disk are referred simply to as hard disk  201 . Other devices involving a plurality of corresponding devices are also referred simply in the same manner. 
   The controller  262  previously determines the size of 1 subblock of the video data to be recorded, the average migration distance La of the head when SCAN schedule is operated, the seek time Ts (L) of a drive of the used hard disk  201 , and the physical format (the number of cylinder, the number of sectors in 1 track, and the number of media which constitutes a cylinder) of the hard disk  201  as the format parameter (determination of the size of the subblock will be described hereinafter with reference to  FIG. 27 ). With reference to this format parameter, the position of each subblock on the hard disk  201  is determined according to the sequence of the steps S 11  to S 5  shown in  FIG. 16 . 
   The average migration distance of the head is given by the following equation (1) from the total number Lt of cylinders of the hard disk  201  and the number of accesses N to be processed in 1 scanning (refer to  FIG. 24(C)  described hereinafter).
 
 La=Lt /( N− 1)  (1)
 
   The seek time Ts (L) of the drive is a function of the seek distance L (the number of cylinders), the value is determined by the mechanical characteristics of the disk drive used.  FIG. 17  shows an example. The number of access requests which are processed collectively in 1 scanning is determined depending on the character of applications used for the disk recorder  2 , the required performance, and the quantity of usable data buffer  212 . The larger the number of access requests N to be scanned collectively is, the more the random access performance of the hard disk is improved, however on the other hand, the larger the necessary quantity of data buffer is, the longer the response time is. 
   The number of subblocks (Bc) in 1 cylinder is calculated in the step S 1  shown in  FIG. 16 . The total number of sectors in 1 cylinder is obtained by multiplying the number of sectors in a track by the number of media. Therefore, Bc is obtained by dividing the total number of sectors in 1 cylinder by the number of sectors necessary to store 1 subblock data. 
   In the step S 2  the gap θgap is calculated. The gap θgap is an angular difference between the head sector and the tail sector of the subblock in the view from the center of the disk. For example, as shown in  FIG. 18 , the head of the shaded subblock is located at the sector “0” of the track “1”, and the tail is located at the sector “6” of the track “2”, therefore the gap θgap is 5/12 of a circumference, namely 5 π/6 radian. 
   The skew θskew is calculated in the step S 3  based on the above-mentioned data. Herein, the skew θskew means the angular difference in the circumferential direction between heads of adjacent subblocks on the hard disk  201  in the view from the center of the disk as shown in  FIG. 19 . First, the data head starts from the position where writing or reading out of 1 subblock was ended and attains to the same angular position in the circumferential direction at the position (track) distant L cylinder distance in the radial direction from the start position, in this case, the time required for the data head to migrate Td (L) is represented by the following equation (2).
 
 Td ( L )( L·Bc·θskew+θgap+ 2· m ·π)/ω  (2)
 
   Herein, L represents the seek distance in the unit of number of cylinders, Bc represents the number of subblocks in 1 cylinder, θskew represents the skew in radian unit, θgap represents the gap in radian unit, ω represents the rotation speed (radian/second) of the hard disk  201 , and m represents an arbitrary integer that makes Td (L) positive. 
     FIG. 20  describes the meaning of the above-mentioned equation (2) on the hard disk  201 . In  FIG. 20 , it is assumed that just now an access to subblock “0” ended. When, the head is located at the angular position A in the view from the center. It is assumed that now the same subblock “0” receives an access again. It takes a time for the disk to rotate the gap θgap, and the waiting time is θgap/ω. 
   Further, to take an access to the head of the subblock “n” located inside by n tracks (subblock) from the subblock “0”, the starting must wait for rotation of the hard disk  201  of the angular sum of n subblock skew (n θskew) from the start position of the subblock “0”. It takes a time of n θskew/ω. Because the hard disk  201  is rotating, the data head attains to the position where the head is located at the time that is obtained by adding integral multiple of the rotational period (Trot) to the time obtained as described herein above. Because the migration through n subblocks is equivalent to the migration through n/Bc cylinders in the expression of the number of cylinders, a graph having the axis of abscissa for the number of cylinder and the axis of ordinate for waiting time for arriving of the head is obtained as shown in  FIG. 21 . The larger the skew θskew is, the larger the gradient of the straight lines is. 
   In the discussion described herein above, it is assumed that the position (angle) of the head in the circumferential direction is constant in the view from the center regardless of the distance from the center. Actually in some cases, the position is not constant exactly depending on the head mechanism, however, the influence is sufficiently small and usually negligible. 
   As shown in  FIG. 21 , the time required for the head of the subblock to attain to the position under the head is obtained for each cylinder by the above-mentioned equation (2). However, because it is required for the head to attain to the desired cylinder within the time, the waiting time is the time from the seek to the time when the head of the block appears first. This time is the overhead Td (L) which involves the seek and rotation waiting both.  FIG. 22  shows an example, and the following equation represents the definition. The actual overhead (waiting time) Td (L) is shown with a thick line in  FIG. 22 . The function of the seek time Ts (L) is shown with a dashed line. In the drawing, Trot is 1 rotation period. 
   In the step S 3 - 1 , the equation (2) and the equation of the straight line for m=0 in  FIG. 21 , namely the equation represented by the following equation (3), are obtained.
 
 Td ( L )=( L·Bc·θskew+θgap )/ω  (3)
 
   The subsequent steps S 3 - 2 , S 3 - 3 , and S 3 - 4  is the step for selecting the skew θskew so that the straight line is always larger than the seek time Ts (L) and approximately touches the seek time Ts (L). 
   In detail, in the step S 3 - 2 , the controller  262  initializes the skew θskew to 0, and in the step S 3 - 3 , the magnitude of the seek time Ts (L) and the overhead Td (L) is compared. If the seek time Ts (L) is determined to be smaller than the overhead Td (L), then the sequence proceeds to the step S 3 - 4 , and the controller  262  increments the skew θskew by delta. The sequence returns to the step S 3 - 3 , the magnitude of the seek time Ts (L) and the overhead Td (L) are compared again. 
   As described herein above, the process of the step S 3 - 3  and the step S 3 - 4  is repeated until the seek time Ts (L) is determined to be equal to the overhead Td (L) or to be larger than the overhead Td (L). When the seek time Ts (L) is determined to be equal to the overhead Td (L) or to be larger than the overhead Td (L), the gradient of the straight line (skew θskew) for m=0 which is located nearest to the seek time Ts (L) and located above the seek time Ts (L) is obtained. 
   In the steps S 4  and S 5 , the position of each subblock on the disk is determined over the entire area of the hard disk  201  using the skew θskew and the gap θgap obtained as described herein above. In the step S 4 , first the pointer of the physical address (cylinder/medium/sector) is initialized to (0/0/0). The next step S 5  is a loop of repetition for all the subblocks, in the internal of the loop, first in the step S 5 - 1 , the logical sector number is obtained from the physical address with reference to the physical address table  302 , and in the step S 5 - 2 , information such as logical sector number and physical address is written on the block map  304 . Thereby, for example, the information of the first subblock (parity data P 1 ) is written on the block map  304  shown in  FIG. 15 . 
   After completion of the above-mentioned steps, the pointer Ppa of the physical address is updated in the step S 5 - 3  in preparation for the next subblock processing. In the step S 5 - 4 , whether all the subblocks are subjected to processing in the steps S 5 - 1  to S 5 - 3  is determined, and if not all the subblocks are subjected to the processing, then un-processed subblocks are subjected to the processing in the steps S 5 - 1  to S 5 - 3 . Herein, the location of the N-th subblock on the hard disk  201  is;
     (1) behind the assigned subblock (in the case that the subblock is assigned sequentially from the outer circumference, on the inner circumference, and in the case that the subblock is assigned sequentially from the inner circumference, on the outer circumference) and   (2) on the area having at the head the sector having the angular difference between the head of the 0-th block nearest to N θskew.   

   Next, the worst overhead in this embodiment is described. 
     FIG. 23  shows the overhead time of the disk on which subblocks are disposed as shown in  FIG. 19 . The axis of abscissa represents the seek distance, namely the number of cylinders L of the hard disk  201  across which the head moves, and the axis of ordinate represents the required time Td (L). The chain line represents the seek time Ts (L), and the solid line represents the total overhead time Td (L). The overhead time is the sum of the seek time Ts (L) and rotation waiting time Trd, the difference between the solid line and the chain line therefore represents the rotation waiting time Trd. 
   Generally, an access request arises anywhere on the hard disk  201 . The place processed in one scanning has bias distribution as shown in  FIG. 24(A)  and  FIG. 24(B) , and conversely in some cases, has even distribution as shown in  FIG. 24C . In the example shown in  FIG. 24 , to move between 6 access requests, 5 random accesses and associated overhead arise. For each the overhead shown in  FIG. 22  with a thick line arises. The total over head for 5 random accesses is worst in the case that all the accesses distribute evenly as shown in  FIG. 24(C)  providing that the overhead function Td (L) is convex upward as shown in  FIG. 23 . The total overhead is smaller than this case when the distribution is bias. In other words, the case that the overhead arises repeatedly at the average migration distance La (=L/5) of the head makes the total overhead worst (maximum). 
   In the step S 3  shown in  FIG. 16 , the skew θskew is selected so that the rotation waiting straight lines given by the above-mentioned equation (2) lies above the seek time Ts (L) and nearest to the seek time Ts (L). Thereby, Td (L) is minimized at the vicinity of the distance La, and the resultant worst overhead Tmax is minimized. 
     FIG. 25  shows the length of overhead schematically in the case in which algorithm is used according to the above-mentioned method (FARAD system). As shown in  FIG. 25 , SCAN system in which a plurality of accesses is executed collectively from the outer circumference to the inner circumference in the order within the range of collected assesses, or conversely, from the inner circumference to the outer circumference in the order can realize the shorter seek time in comparison with conventional system in which access is executed in the order of arising, and therefore the overhead can be the shorter. However, this SCAN system can shorten the seek time in comparison with the conventional system, but can not shorten the rotation waiting time. On the other hand, the above-mentioned method (FARAD system) can shorten not only the seek time as well as the SCAN system but also the rotation waiting time in comparison with the conventional system (SCAN system), and thus the total overhead can be shortened in comparison with SCAN system. 
   As described herein above, in this embodiment, it is possible to suppress the overhead Td (L) for the head average migration distance La to the minimum by selecting the skew θskew and the gap θgap properly (so that the skew θskew corresponds to the gap θgap), and the rotation waiting time is minimized. In the process of the flow chart shown in  FIG. 16 , it is assumed that the size of the subblock is a given fixed value, but the size of the subblock is optional within a certain range. In this case, both the gap θgap and the skew θskew can be changed, the position of the straight line can be controlled more finely so as to be nearer to the seek time at the vicinity of the average migration distance La. This point will be described in detail hereinafter. 
   By applying the above-mentioned method, the overhead associated with migration between subblocks is improved greatly. However, in the case that the size of a subblock is large extending over a plurality of tracks and plurality of cylinders, the required time for changing track and migration time to the adjacent cylinder should be take into consideration. Because the required time for changing track and migration to the adjacent cylinder are constant respectively, by giving skew between tracks and between cylinders so that the data arrives just under the head after the time, the long rotation waiting time in a subblock associated with changing track and migration to the adjacent cylinder is suppressed. 
   Next, the scheduling process for determining the access order of the head so that the migration distance of the head is minimized operated by the controller  262  is described.  FIG. 26  shows a flow chart for operating the scheduling process. The controller  262  controls the SCSI controller  202  in the step S 11 , and the head of the hard disk  201  is migrated to the cylinder “#0”. Next, the sequence proceeds to the step S 12  in which scheduling is operated actually. 
   In the step S 12 - 1  in the step S 12 , the controller  262  reads N access requests from the built-in access request buffer (not shown in the drawing) in the order of time from the earliest (old). In the access request buffer, access requests supplied from the host personal computer  3  are stored in the order of input. One access request has a subblock number to be subjected to access and the head address of the data buffer  212  used for data transfer. Number N is a constant which is given from the host personal computer  3  previously. 
   In the step S 12 - 2 , the controller  262  refers to the block map  304  for respective N access requests, and finds physical addresses (cylinder number, medium number, and sector number) of the subblocks to be subjected to access. Next, in the step S 12 - 3 , N access requests are re-arranged in the order of cylinder number from the smallest (from the outer circumference to the inner circumference). This operation realizes the SCAN algorithm schedule. 
   In the step S 12 - 4 , re-arranged these access requests are sent out to the hard disk  201  through the SCSI controller  202  in the order from the access request having the smallest cylinder number, and access and data transfer are operated actually. An access indication for one subblock is sent out, and after completion of data transfer in the step S 12 - 6 , then the next access indication is sent out. Whether transfer of all the requests is completed is determined in the step S 12 - 6 , if not all the requests are transferred, the sequence returns to the step S 12 - 4 , the same processing is operated. Such process is repeated N times, processing of the N access requests is determined to be completed in the step S 12 - 6 . 
   Next, in the step S 12 - 7 , completion of processing of the N access requests is informed to the host personal computer  3 , and a series of processing relating to the N access requests is brought to an end. 
   Further, in the final step S 12 - 8 , whether all the access requests are processed completely and the access request buffer has been empty is determined. If there is some residual access requests, then the controller  262  returns to the step S 12 - 1 , and reads out the next N access requests and continues processing. If N access requests are not in the access request buffer, then the controller waits for accumulation of N requests in this step, and after completion of N request accumulation, the sequence returns to the step S 12 - 1 , and the same processing is operated. 
   Further, for example, the controller  262  improves the real time response speed of access additionally by changing the size of subblock so that the gap θgap is constant over the entire area from the outside to the inside of the hard disk  201 . 
   Next, with reference to flow charts shown in  FIG. 27  to  FIG. 32 , the process sequence in which the controller  262  arranges the k-th subblock on a prescribed track of a prescribed hard disk  201  is described. 
   First in the step S 31 , total n+1 hard disks  201  for storing the parity data served as error correction data and data of n subblocks are selected out of total m hard disks  201  (in the case of the embodiment shown in  FIG. 7 , m=32). In the example, first hard disks  201  in which the parity data is to be stored is selected, and next hard disks  201  on which the data of subblocks is arranged sequentially from the inner circumference and hard disks  201  on which the data of subblocks is arranged sequentially from the outer circumference are selected. 
   Numbers from 1 to n are assigned to respective subblocks, for example, subblocks having an odd number are arranged sequentially from the inner circumference on a hard disk  201 , and subblocks having an even number are arranged sequentially from the outer circumference on a hard disk  201 . The data is arranged on a hard disk  201  with changing the hard disk depending on the data to avoid concentrated distribution of subblocks on a limited number of hard disks  201 . 
     FIG. 28  is the flowchart for describing the detailed processing of the step S 31  shown in  FIG. 27 . In detail, in the step S 41 , a hard disk  201  having the number j represented by the following equation (4) is selected as a hard disk  201  on which the parity data is arranged.
   j=MOD ( k− 1 ,m )+1  (4) 
   Herein, MOD is an operator for calculating the remainder formed when k−1 is divided by m (the total number of hard disks  201 ). 
   By operating this processing, for example it is assumed that the number of hard disks  201  m is 32, hard disks  201  are selected in the order such as, j=1, 2, 3, . . . , 31, 32, 1, 2, . . . . 
   Next, in the step S 42 , the j-th hard disk  201  represented by the following equation (5) is selected as a hard disk  201  on which the i-th (i=1, 3, 5, . . . ) subblock data is arranged sequentially from the inner circumference.
 
 j=MOD (k+i−1 ,m )+1  (5)
 
   Thereby, for example, in the case of i=1 (the first subblock is recorded), hard disks  201  are selected in the order of j, such as 3, 4, 5, . . . , 32, 1, 2, . . . , and in the case of i=3 (the third subblock is recorded), hard disks  201  are selected in the order such as 4, 5, 6, . . . , 32, 1, 2, . . . . 
   Next, the sequence proceeds to the step S 43 , the j-th hard disk  201  represented by the above-mentioned equation ( 5 ) is selected as a hard disk  201  on which the i-th (i=2, 4, 6, . . . ) subblock data is arranged sequentially from the outer circumference. 
   Thereby, for example, in the case of i=2 (the second subblock is recorded), hard disks  201  of j=3, 5, . . . , 32, 1, 2, . . . are selected, and in the case of i=4 (the fourth subblock is recorded), hard disks  201  of j=5, 6, 7, . . . , 32, 1, 2, . . . are selected sequentially. 
   As described herein above, by using tracks on the outer circumference and tracks on the inner circumference alternately in the form of pair, it is possible to make the size of subblock on the inner circumference smaller than the size of subblock on the outer circumference, and the gap θgap of subblocks is made constant. 
   In the flow chart shown in  FIG. 28 , subblocks which are arranged sequentially from the inner circumference and subblocks which are arranged sequentially from the outer circumference are determined alternately for arranging the subblock data, however, alternation is not necessarily required as long as the arrangement is in good balance. In detail, subblocks are arranged sequentially from the inner circumference in the order on a hard disk  201 , and the next residual subblocks are arranged sequentially in the order from the outer circumference on the hard disk  201 . 
   Further, j-th hard disk  201  represented by the above-mentioned equations (4) and (5) is not necessarily selected as long as subblocks are distributed concentratedly on a limited number of hard disks  201 . For example, hard disks  201  on which subblocks are arranged sequentially from the inner circumference are selected out of hard disks  201  where the inner circumference is used not heavily, on the other hand, hard disks  201  on which subblocks are arranged sequentially from the outer circumference are selected out of hard disks  201  where the outer circumference is used not heavily, this method is effective. Anyway, the parity data is arranged sequentially from the outer circumference on the hard disk  201  selected in the step S 41 . 
   As described herein above the hard disk  201  is determined, then the sequence returns and proceeds to the step S 32  shown in  FIG. 27 . 
   In the step S 32 , the start logical sector from which arrangement of the parity data and subblock data starts is determined on each hard disk  201 . 
     FIG. 29  is a flow chart for describing process sequence for determining the start logical sector. First in the step S 51 , the start logical address Lkp is obtained on a hard disk  201  on which the parity data is arranged sequentially from the outer circumference. 
     FIG. 30  is a flow chart for describing the detailed processing in the step S 51  shown in  FIG. 29 . First in the step S 61 , the outermost track out of non-arranged areas where no subblock (parity data) is arranged is selected as the track on which the subblock (in this case, parity data) is to be arranged. Non-arranged areas are found based on the allocation map  303 . Thereby, the cylinder number (CYlki) and medium number (MEDki) of the physical sector address are determined, and the number of sectors (Tki) per 1 track on this map location is found with reference to the ZBR table  301 . 
   Next, in the step S 62 , based on the cylinder number (CYLki) and the optimal skew (θskew) value and the following equation (6), the angle Oki (the number of cylinders between both tracks is CYLki) between the head of the outermost circumferential track (cylinder number CYLki) in the non-arranged areas selected in the step S 61  and the head of the physical outermost circumferential track (track on which the data of the first subblock is recorded) (track having the cylinder number  0 ) is calculated.
 
θ ki =θskew×CYLki  (6)
 
   However, if θki&gt;2π, then processing θki=θki−2π is repeated until the relation θki&lt;2π is satisfied. 
   Next, the sequence proceeds to the step S 63 , and using the angle θki calculated by the equation (6) and the number of sectors per 1 track (Tki), and based on the following equation (7), the sector number (SECki) is calculated.
 
 SECki=ROUNDUP ( Tki×θki/ 2π)  (7)
 
   Herein ROUNDUP represents an operator for calculating an integer which is obtained by rounding-up a fraction. 
   Next in the step S 64 , with reference to the physical address table  302  ( FIGS. 13A and 13B ), the logical sector address (Lki) (in this case, Lkp) is determined from the physical sector address (CYLki, MEDki, SECki) calculated in the process of the steps S 61  to S 63 , and the sequence proceeds to the return. 
   Next, the sequence proceeds to the step S 52  shown in  FIG. 29 , the start logical sector address Lki (i=1, 3, 5, . . . ) is calculated respectively for all the hard disks  201  of successive arrangement from the inner circumference. 
     FIG. 31  is a flow chart for describing the detailed processing in the step S 52  shown in  FIG. 29 . First in the step S 71 , the innermost circumferential track on the non-arranged areas is selected with reference to the physical address table  302  ( FIGS. 13A and 13B ) as a track on which subblocks are arranged. Thereby, the cylinder number (CYLki) and medium number (MEDKki) of the physical sector address are determined, and the number of sectors (Tki) per 1 track at the map location is found with reference to the ZBR table  301 . 
   Next in the step S 72 , an angle θki between the head of the innermost circumferential track on the non-arranged areas selected in the step S 71  and the head of the physical innermost circumferential track (the track on which the data of the first subblock is recorded) is determined, and then the sector number (SECki) is determined in the step S 73 . In the step S 74 , the logical sector address (Lki) is determined based on the determined physical sector address (CYLki, MEDki, SECki), and the sequence proceeds to the return. The above-mentioned processing in steps S 72  to S 74  is basically the same as the processing in the steps S 62  to S 64  shown in  FIG. 30  excepting that the track is selected sequentially from the inner circumference instead of the outer circumference, and the detailed description is omitted. 
   Next, the sequence proceeds to the step S 53  shown in  FIG. 29 , the start logical sector address Lki (i=2, 4, 6, . . . ) for all the hard disks  201  on which the data of subblocks is arranged sequentially from the outer circumference is determined respectively. The process sequence is the same as that described hereinbefore with reference to the flow chart shown in  FIG. 30 , and the detailed description is omitted. After completion of the processing, the sequence proceeds to the return. 
   In the exemplary processing shown in  FIG. 29  to  FIG. 31 , the track on which subblocks are arranged is selected out of the outermost circumferential tracks on the non-arranged areas in the case that subblocks are arranged sequentially from the outer circumference on tracks, and the track on which subblocks are arranged in selected out of the innermost circumferential tracks on the non-arranged areas in the case that subblocks are arranged sequentially from the inner circumference on tracks, however, the outermost circumferential track and the innermost circumferential track are not necessarily selected. Because for example, in the case of ZBR format, the number of sectors per 1 track is the same as long as they are in the same zone, and the size of subblocks and the gap value are the same respectively. 
   The start logical sector address is determined as described herein above, and next, the sequence proceeds to the step S 33  shown in  FIG. 27 , and the parity data and the size of subblocks are determined. The process sequence to determine the size of subblocks will be described hereinafter with reference to the flow chart shown in  FIG. 32 . 
   Next, what size (the number of sectors) of subblocks (including the case of parity data) should be is considered. First, the sum of the size of subblocks is equal to the data size of original 1 block. In detail, assuming that the size of subblocks (the number of sectors) is Ski (i=1, 2, 3, . . . , n) and the data size (the number of sectors) of original  1  block is S, then S is represented by the following equation (8).
 
 Sk 1 +Sk 2+, . . . , + Skn=S   (8)
 
   On the other hand, the read out time or writing time of respective subblocks is to be equal, the gap value of respective subblocks should be equal. In other words, the following equation (9) should hold.
 
 Sk 1 /Tk 1= Sk 2 /Tk 2=, . . . , = Skn/Tkn   (9)
 
   In the above-mentioned equation (9), Tki (i=1, 2, 3, . . . , n) is the number of sectors of a track on which i-th subblock is arranged. 
   From the equation (8) and the equation (9), the number of sectors Ski of subblocks which results in the same gap θgap value for respective subblocks is given by the following equation (10).
 
 Ski=S×Tki/T   (10)
 
   wherein T=Tk1+Tk2+, . . . , +Tkn. 
   The number of sectors Ski is given actually in the form of integer, the respective size requires some fine adjustment. 
   On the other hand, the size of parity data Skp is given by the following equation (11) if the size of subblocks has been determined.
 
 Skp =MAX( Sk 1 , Sk 2 , . . . , Skn )  (11)
 
   In the equation (11), MAX is an operator to determine the largest number of sectors among the size of subblocks Sk 1  to Skn. 
   Because it is ensured that the parity data is arranged on the outer circumferential track of a hard disk  201  based on the operation in the step S 31  and the step S 32  shown in  FIG. 27 , it is obvious that the following equation (12) holds.
 
 Sk 1 /Tk 1 =Sk 2 /Tk 2=, . . . , = Skn/Tkn=Skp/Tkp   (12)
 
   wherein Tkp is the number of sectors of the track on which the subblock Skp is arranged. 
     FIG. 32  shows a flow chart for realizing the sequence for determining the above-mentioned subblock size. First in the step S 81 , the sum of the number of sectors Tki (i=1, 2, . . . , n) per 1 track of the track corresponding to the map location where n subblocks are arranged is calculated. Next, the calculation represented by the above-mentioned equation (10) is operated for the variable i of 1 to n, and the size Ski (i=1, 2, . . . , n) of respective subblocks is obtained. 
   Next, the sequence proceeds to the step S 82 , the calculation represented by the above-mentioned equation (8) is operated, and whether the sum of the size Ski of respective subblocks obtained in the step S 81  is equal to the data size S of original 1 block is determined. If the sum of the size Ski of respective subblocks is determined to be not equal to the data size S of original 1 block, then the sequence proceeds to the step S 83 , and the size Ski of respective subblocks is slightly changed so that the sum of the size Ski of respective subblocks becomes equal to the data size S of original 1 block. Then, the sequence returns to the step S 82 , the processing of the step S 82  and the step S 83  is repeated until the sum of the size Si of respective subblocks is determined to be equal to the data size S of original 1 block. on the other hand, if the sum of the size Ski of respective subblocks is determined to be equal to the data size S of original 1 block, then the sequence proceeds to the step S 84 , the size Skp of the parity data is obtained. In detail, the largest size among subblocks Ski is regarded as the size Skp of the parity data. 
   After completion of the processing in the step S 84 , the sequence proceeds to the return. Thus, the processing of the step S 33  in the flow chart shown in  FIG. 27  is completed, and all the processes are completed. 
   As described herein above, the size of subblocks arranged on the inner circumference is made smaller and the size of subblocks arranged on the outer circumference is made larger so that the gap θgap of respective subblocks is equal to each other on respective hard disks  201 . 
     FIG. 33  shows an example of subblocks distributed on hard disks  201  in the manner as described herein above. Herein, the number of hard disks m is 6, and the number of subblocks is 4. 
   The parity data on the first frame is arranged on the hard disk  201 - 1 , and the corresponding 4 subblocks are arranged separately on the hard disks  201 - 2  to  201 - 5 . The parity data arranged on the hard disk  201 - 1  and subblocks arranged on the hard disks  201 - 3  and  201 - 5  are placed on the outermost track, and subblocks arranged on the hard disks  201 - 2  and  201 - 4  are placed on the innermost track. 
   The parity data on the second frame is arranged on the hard disk  201 - 2 , and subblocks are arranged on the hard disks  201 - 3  to  201 - 6 , and the respective locations are on outer circumference, inner circumference, outer circumference, inner circumference, and outer circumference in the order. The parity data on the third frame is arranged on the hard disks  201 - 3 , and subblocks are arranged on the hard disks  201 - 4  to  201 - 6  and hard disk  201 - 1 , and the respective locations are on the outer circumference, inner circumference, outer circumference, inner circumference, and outer circumference in the order. Similarly in the following, the data on respective frames is arranged, and the data on the last frame is arranged, for example, on the hard disks  201 - 3  to  201 - 6  and hard disk  201 - 1  on the middle of the cylinder. 
   Based on insight into the parity data and subblocks arranged on one hard disk  201 , it is found that the time required to read out and write subblocks is approximately equal because the gap θgap value of respective subblocks is approximately equal. 
   In the above-mentioned embodiment, the actual time required to read out and write the parity data and subblocks is made equal regardless of the location of data stored on a hard disks  201  as described herein above. 
   Further, in the above-mentioned embodiment, the data is scanned from the outer circumference to the inner circumference for access to the data, however alternatively, the data may be scanned from the inner circumference to the outer circumference. In this case, the optimal skew for access to data can be set with migrating the head from the inner circumference to the outer circumference. 
   Next, the operation of the RAID controller  282  for generating the parity data and correcting errors using the parity data is described. For example, as shown in  FIG. 15 , the size of a subblock recorded on the outer circumference is larger than the size of a subblock recorded on the inner circumference, and one block is divided into  4  subblocks # 1  to # 4 . 
   The size of a parity data is set so as to be equal to the size of the largest subblock among divided subblocks. 
   Basically, the j-th parity data Pj is formed from the j-th data of respective subblocks. As shown in  FIG. 34A , in the case that the value of j is small, because j-th data corresponding to all the subblocks exist, the parity data Pj is formed from the data of all the subblocks #1 to #4. On the other hand, in the case that the value of j is larger as shown in  FIG. 30(B) , no j-th data of subblocks #1 and #3 exist. 
   In such case, the parity data Pj is formed from subblocks #2 and #4 having the size of j or larger based on the j-th data. Alternatively, the pre-determined prescribed data is added to the subblocks #1 and #3, and the parity data Pj is formed from the data of all the subblocks. Various algorithms for forming the parity data have been known, however, it is not necessary to discuss the detail and the description is omitted. 
   Next, the operation for correcting errors are described herein under. For example, in the case that the j-th data of a certain subblock is an error, basically the error is corrected using the j-th data of other subblocks and parity data. For example, as shown in  FIGS. 35A and 35B , in the case that the value of j is small, because the parity data is formed from the j-th data of all the subblocks, the erroneous jth data of the subblock #4 is corrected using the j-th data of the parity data and the non-erroneous j-th data of all the subblocks #1 to #3. 
   On the other hand, as shown in  FIG. 35B , in the case that the value of j is larger, because the parity data is formed from the j-th data of subblocks having the size of j or larger, the erroneous j-th data of the subblock #4 is corrected using the non-erroneous subblock #2 among subblocks having the size of j or larger and the parity data. 
   In this embodiment, forming of such parity data and error correction processing using the parity data are carried out in real time.  FIG. 36  shows the structure for operating such processing. 
   As shown in  FIG. 36 , the RAID controller  282 - 1  of the video block  271 - 1  is provided with delay elements  401 - 1  to  403 - 1  for delaying the data by 1 packet transfer block. The RAID controller  282 - 1  generates the parity data from the pixel data supplied from the video processing section  283 - 1  though a 10 bit bus, supplies it to the FIFO  404 - 1  though a 32 bit bus, and supplies the pixel data to the FIFO  405 - 1  though a 32 bit bus. The RAID controller  282 - 1  processes the pixel data (reproduction data) supplied from the DMA controller  281 - 1  though a 64 bit bus and an FIFO  406 - 1  for error correction based on the parity data, and supplies it to the video processing section  283 - 1  in 10 bit pixel data unit. 
     FIGS. 37A and 37B  show an exemplary table of a conversion processing of 10 bit data and 32 bit data in the RAID controller  282 - 1 . In the case that the first mode is set, when the data is supplied in 10 bit unit to the RAID controller  282 - 1  from the video processing section  283 - 1  as shown in  FIG. 37A , the RAID controller  282 - 1  collects 3 10 bit unit data, and interpolates a 1 bit dummy data of 0 between the first 10 bit data and second 10 bit data and interpolates a 1 bit dummy data of 0 between the second 10 bit data and the third 10 bit data to form the data of total 32 bits. Conversely, when a 32 bit data is supplied from the bus, the RAID controller  282 - 1  divides the 32 bit data into 3 divided data of 10 bits with exclusion of the 11-th bit and the 22nd bit, and processes the divided data. 
   On the other hand, in the case that the second mode is set, the RAID controller  282 - 1  ignores the lower 2 bits out of the input data of 10 bits as shown in  FIG. 37B , and combines 4 groups of 8 bit data to from a 32 bit data. Conversely, when a 32 bit data is supplied, the RAID controller  282 - 1  divides this data into data of 8 bits, adds 2 bit dummy data to each 8 bit data to from 10 bit data. 
   The RAID controller  282 - 1  and the DMA controller  281 - 1  are connected each other through FIFO&#39;s  404 - 1  to  406 - 1 . The RAID controller  282 - 1  side of the FIFO&#39;s  404 - 1  to  406 - 1  is structured with a 32 bit bus, and the DMA controller  281 - 1  side is structured with a 64 bit bus. Because each FIFO has 32 bit structure, for example, the FIFO  404 - 1  delivers the 32 bit parity data supplied first to the DMA controller  281 - 1  through, for example, the higher 32 bit bus of the 64 bit bus, and supplies the next input 32 bit parity data to the DMA controller through the lower 32 bit bus of the 64 bit bus. 
   The FIFO  405 - 1 , similarly to the FIFO  404 - 1 , delivers the first 32 bit pixel data supplied from the RAID controller  282 - 1  to the DMA controller  281 - 1  through the MSB side 32 bit bus of the 64 bit bus, and delivers the next input 32 bit pixel data to the DMA controller  281 - 1  through the LSB side 32 bit bus of the 64 bit bus. 
   On the other hand, the FIFO  406 - 1 , which supplies the pixel data (reproduction pixel data) supplied from the DMA controller  281 - 1  through the 64 bit bus to the RAID controller  282 - 1 , comprises FIFO&#39;s  406 A- 1  and  406 B- 1  having respectively 32 bit capacity as shown in  FIG. 38 . The pixel data supplied from the DMA controller  281 - 1  though the MSB side 32 bit bus of the 64 bit bus is supplied to the FIFO  406 A- 1 , and the pixel data supplied through the LSB side 32 bit bus is supplied to the FIFO  406 B- 1 . The pixel data stored in the FIFO  406 A- 1  is supplied to the RAID controller  282 - 1  through the 32 bit bus, thereafter, the 32 bit pixel data stored in the FIFO  406 B- 1  is read out and supplied to the RAID controller  282 - 1  through the 32 bit bus. 
   The DMA controller  281 - 1  is connected to the 64 bit DMA bus  251 . The FIFO  407 - 1  is connected to the 32 bit control bus  252 , and which delivers a command supplied through the control bus  252  to the RAID controller  282 - 1 . 
   Though the drawing is omitted, video blocks  2712  to  271 - 6  have the same structure as the video block  271 - 1 . 
   A board  421 - 1  is provided with  3  SCSI boards  431 - 1  to  431 - 3 . The SCSI board  431 - 1  is provided with a data buffer  212 - 1  structured with an S-DRAM, and input output operation is controlled by the buffer controller  211 - 1 .  2  SCSI controllers  202 - 1  and  202 - 2  are connected to the buffer controller  211 - 1  through the 32 bit bus, and the SCSI controller  202 - 1  controls  2  hard disks  201 - 1  and  201 - 2 . Further, the SCSI controller  202 - 2  controls  2  hard disks  201 - 3  and  201 - 4 . 
   Though the drawing is omitted, also the SCSI boards  431 - 2  and  431 - 3  have the same structure as the SCSI board  431 - 1 . Further, boards  421 - 2  and  431 - 3  also have the same structure as the board  421 - 1 . Therefore, in this exemplary structure, one board  421 -i can controls 12 hard disks  201 , and actually 3 boards are provided, total 36 hard disks  201  can be controlled. However, actually 32 hard disks  201  are connected. 
   As described herein above, the image data of 1 frame is divided into, for example, 4 subblocks, each subblock is further divided into packet transfer block in 128 word pixel data unit, and generation of parity data and error correction process using the parity data are performed. 
   In detail, for example, the NTSC image data of 1 frame comprises 1440×512 pixels as shown in  FIG. 39 . One pixel comprises 10 bit luminance (Y) data and 10 bit chrominance (U or V) data. 
   Because 1 word comprises 32 bits, 3 luminance data of 10 bits are loaded on 1 word. 2 bit dummy data is added between 3 luminance data as shown in  FIG. 37A , thereby 3 pixel data is loaded on 1 word. From such view point, 384 pixel data is loaded on 1 packet transfer block as shown in  FIG. 40 . 
   However, in view of the structure that 1 pixel data comprises 10 bit luminance data and 10 bit chrominance data, 1.5 pixel data is loaded on 1 word, and then the number of pixels loaded on 1 packet transfer block (128 word) is 192-pixel data. 
   Herein for simple description, it is assumed that 1 pixel comprises 10 bit luminance data and 384 pixel are loaded on 1 packet transfer block. 
   As described herein above, the DMA controller  281  performs DMA transfer in packet transfer block unit between the RAID controller  282  and the data buffer  212 .  FIG. 41  shows an example of an DMA command supplied from the controller  262  to DMA controller  281  through the control bus  252 . This example exemplifies an example of a command for DMA transfer of the pixel data to be recorded from the RAID controller  282  to the data buffer  212 . 
   As shown in  FIG. 41 , this DMA command is composed of commands and operands, the operand stores the address of the data buffer  212  for recording the pixel data. The command specifies the number of transfer of the packet transfer block (the number of loops). 
   Other commands for indicating various control other than that for specifying the number of loops may be loaded as the command. For example, the RAID ratio is set to the command for the RAID controller  282 . 
   For example, it is assumed that 1 frame pixel data is divided sequentially from the upper left to lower right for every 1 packet transfer block, like as, A 0 , B 0 , C 0 , D 0 , A 1 , B 1 , C 1 , D 1 , . . . . When the packet transfer block is indicated to be transferred to the DMA controller  281  with the DMA command as shown in  FIG. 41 , the DMA controller  281  receives this command at the FIFO  501 - 1 , and writes the data on the data buffer  212  as shown in  FIG. 42 . 
   In detail, as shown in  FIG. 41 , addresses a 0  to d 0  of the data buffer  212  are specified on operands of the command corresponding to 4 subblocks, and p 0  is specified on an operand as the address of the data buffer  212  where the parity data corresponding to 4 subblocks to be recorded. The number of loops n is written as the command. In this case, as shown in  FIG. 42 , the packet transfer block A 0  is written on the address a 0  of the data buffer  212 . The packet transfer block B 0  is written on the address b 0 , the packet transfer block C 0  is written on the address c 0 , and the packet transfer block D 0  is written on the address d 0 . The parity data P 0  for the first 1 packet transfer block out of the parity data formed correspondingly to 4 subblocks is written on the address p 0  of the data buffer  212 . 
   Next, the packet transfer block Al is written on the address a 0 +128 (word) of the data buffer  212 , the packet transfer block B 1  is written on the address b 0 +128, the packet transfer block C 1  is written on the address c 0 +128, and the packet transfer block D 1  is written on the address d 0 +128. Further, the parity data P 1  is written on the address p 0 +128. 
   Similarly in the following, data A 0 , A 1 , A 2 , . . . , A(n−1) are written on the area which is continuous from the address a 0 , and data B 0 , B 1 , B 2 , . . . , B(n−1) are written on the area which is continuous from the address b 0 . Further, data C 0 , C 1 , C 2 , . . . , C(n−1) are written on the area which is continuous from the address c 0 , data D 0 , D 1 , D 2 , . . . , D(n−1) are written on the area which is continuous from the address d 0 , and parity data P 0  to P(n−1) are written in the area which is continuous from the address p 0 . 
     FIG. 43  shows the range of the area R 1  to which the pixel data of 1 frame image is transferred with 4:1 RAID and the area R 2  of 2:1 RAID. As shown in  FIG. 43 , successive packet blocks A 0 , B 0 , C 0 , D 0 , A 1 , D 1 , C 1 , D 1 , . . . , An, Bn, Cn, Dn are transferred with 4:1 RAID as shown in  FIG. 43 . The following packet transfer blocks of the area R 2  A(n+1), C(n+1), A(n+2), C(n+2), . . . , Ar, Cr are transferred with 2:1 RAID. 
   The above-mentioned packet transfer blocks Ai, Bi, Ci, and Di constitute respectively the first to fourth subblocks. 
   In detail, as shown in  FIG. 44 , the first subblock consists of packet transfer blocks A 0  to Ar, the second subblock consists of packet transfer blocks B 0  to Bn, the third subblock consists of packet transfer blocks C 0  to Cr, and the fourth subblock consists of packet transfer blocks D 0  to Dn. The parity data consists of packet transfer blocks PO to Pr. 
   As it is obvious from the comparison between  FIG. 43  and  FIG. 44 , for example, the packet transfer block Ai which constitute the first subblock does not consist of successive pixels on 1 frame image shown in  FIG. 43  but consists of pixels which are distributed on prescribed positions (of course, in a packet transfer block, pixels are successive). 
   As shown in  FIG. 44 , (n+1) packet transfer blocks of each subblock constitute 4:1 RAID together with (n+1) parity data. 
   On the other hand, packet transfer blocks from the packet transfer block An+1 to the packet transfer block Ar of the first subblock, packet transfer subblocks from the packet transfer block Cn+1 to the packet transfer block Cr of the third subblock, and the parity data form the packet transfer block Pn+1 to the packet transfer block Pr constitute 2:1 RAID. 
   The DMA command as shown on the left side of  FIG. 44  is served to DMA-transfer the packet transfer block on the area of 4:1 RAID to the data buffer  212 . In detail, the data A 1  of the first subblock is stored in the address a 0  of the data buffer  212 , the packet transfer block B 1  of the second subblock is stored in the address b 0  of the data buffer  212 , the packet transfer block C 1  of the third subblock is stored in the address c 0  of the data buffer  212 , and the packet transfer block D 1  of the fourth subblock is stored in the address d 0  of the data buffer  212 . Next, the second packet transfer blocks A 2 , B 2 , C 2 , and D 2 , and the parity data P 2  are transferred sequentially. Similarly in the following, n+1 transferring is performed for the packet transfer blocks on the 4:1 RAID area. 
   On the other hand, the DMA command shown in the right side of  FIG. 44  is served to DMA-transfer packet transfer blocks on 2:1 RAID area to the data buffer  212 . In detail, the packet transfer block An+1 of the first subblock is stored in the address a 0  of the data buffer  212 . Similarly, the packet transfer block Cn+1 of the third subblock is stored in the address c 0  of the data buffer  212 , and the parity data Pn+1 is stored in the address p 0  of the data buffer  212 . Similarly in the following, the second and following packet transfer blocks An+2, Cn+3, Pn+2, An+3, Cn+3, +n+3, . . . are transferred sequentially. When, the number of transferring of the packet transfer block is r−n+2. 
     FIG. 45  and  FIG. 46  shows the DMA command for reading out the packet transfer block from the data buffer  212 .  FIG. 45  shows the case that there is no error in packet transfer blocks, and  FIG. 46  shows the case where there are some errors. 
   As shown in  FIG. 45 , in the cast where there are no error in the packet transfer blocks, addresses a 0  to d 0  of the data buffer  212  in which each packet transfer block is stored and the number of transferring are written. In detail, in this case, one packet transfer block of the first subblock is read out from the address a 0  of the data buffer  212 , one packet transfer block of the second subblock is read out from the address b 0 , one packet transfer block of the third subblock is read out from the address c 0 , and one packet transfer block of the fourth subblock is read out from the address d 0 . Such reading out operation is repeated the number of times equivalent to the number of loops. 
   On the other hand, as shown in  FIG. 46 , for example, in the case that there are some errors in the packet transfer block of the third block, the address p 0  where the parity data is stored is written instead of the address c 0  where the erroneous packet transfer block is stored. The number of loops is indicated as a command, and a flag which indicates that there is an error in the data of third subblock stored in the address c 0  is written. Therefore, in this case, the data of the third subblock is not read out from the data buffer  212 , and the parity data is read out instead. 
   Next, detailed structure and operation in which the RAID controller  282  generates the parity data in real time and error correction is performed using the parity data in real time are described.  FIG. 47  shows an exemplary partial structure of the RAID controller  282  for generating the parity data in real time and performing error correction using the parity data. 
   A selector  451  selects any one of the recording data (pixel data) supplied from the video processing section  283  and the pixel data (reproduction data) supplied from the data buffer  212 , supplies it to other circuits not shown in the drawing as the input data, and supplies it to the delay element  401 - 4  and to the input A of selectors  454  and  455 . The delay element  401 - 4  delays the input data by 1 packet transfer block, and then delivers it to the subsequent delay element  4013 . The delay element  401 - 3  also delays the input data by 1 packet transfer block, and then delivers it to the subsequent delay element  401 - 2 . The delay element  401 - 2  also delays the input data by 1 packet transfer block, and then delivers it to the subsequent delay element  401 - 1 . The delay element  401 - 1  delays the input data by 1 packet transfer block, and then delivers it to the input A of the selector  453 . 
   Four delay elements namely delay elements  401 - 1  to  401 - 4  are shown in the block diagram of  FIG. 47 , however, actually only one delay element  401  is shown in  FIG. 36 , and in this case, this delay element  401  is used repeatedly the number of times equivalent to the number of loops (in this case, four), thereby the delay of the packet transfer block equivalent to the number of loops can be obtained. 
   The selector  454  selects any one of the input B to which the output of the delay element  402  is supplied and the input A to which the output of the selector  451  is supplied, or calculates the exclusive OR of 2 inputs and delivers it to the delay element  402 . The output of the delay element  402  is supplied to the input A of the selector  452 . 
   Also, the selector  455  selects any one of the input A to which the output of the selector  451  is supplied and the input B to which the output of the delay element  403  is supplied, or calculates the exclusive OR of 2 inputs and delivers it to the delay element  403  and delivers it to a circuit not shown in the drawing as the parity data. The output of the delay element  403  is supplied to the input B of the selector  452 . 
   The selector  452  selects any one of the input A and input B, and supplies it to the input B of the selector  453 . The selector  453  selects any one of the input A from the delay element  401 - 1  and the input B from the selector  452 , and supplies the selection result to the video processing section  283 . 
   Next, operation for generating the parity data is described with reference to  FIG. 48 . When the pixel data to be recorded in the data buffer  212  is supplied from the video processing section  283  to the RAID controller  282 , the RAID controller  282  converts the input from the data in 10 bit unit to the data in 32 bit (1 word) unit. Further, the RAID controller  282  collects the data equivalent to  128  words (equivalent to 1 packet transfer block), and supplies the recording data to the input A of the selector  451 . Herein, it is assumed that the number of the packet transfer block which is entered first is 0. The packet transfer block of the number 0 is selected by the selector  451 , supplied to the input A of the selector  455 , and delivered to the circuit not shown in the drawing as the input data. When, because the packet transfer block is not yet held in the delay element  403 , the selector  455  selects the input A as it is. The output of the selector  455  (the packet transfer block of number 0) is supplied to the delay element  403  to be held. The above-mentioned operations are summarized in  FIG. 48 . 
   Next, when the packet transfer block of number 1 is supplied to the selector  451 , the selector  451  selects this packet transfer block, and supplies it to the selector  455 . Because the packet transfer block of number 0 held in the delay element  403  has been supplied to the input B of the selector  455 , the selector  455  calculates the exclusive OR of the packet transfer block of number 1 supplied from the selector  451  and the packet transfer block of number 0 supplied from the delay element  403 , and supplies it to the delay element  403  to be held. 
   Similarly in the following, as shown in  FIG. 48 , when the packet transfer block of number 2 is supplied to the selector  451 , the selector  455  calculates and delivers the exclusive OR of packet transfer blocks of number 0, number 1, and number 2, and further when the packet transfer block of number 3 is entered, the exclusive OR of packet transfer blocks of number 0 to number 3 is calculated and delivered. In the case of 4:1 RAID, this output is the parity to be obtained. 
   Similarly in the following, when a packet transfer block of a new number is entered sequentially, as shown in  FIG. 48 , the parity data is formed and delivered sequentially in real time. 
   The input data selected by and delivered from the selector  451  is supplied from the RAID controller  282  to the FIFO  405 - 1  through the 32 bit bus, and supplied to the DMA controller  281  through the 64 bit bus. The parity data delivered from the selector  455  is supplied from the RAID controller  282  to the FIFO  404 - 1  through the 32 bit bus, and further supplied therefrom to the DMA controller  281  through the 64 bit bus. 
   A DMA command as shown in  FIG. 41  has been entered from the controller  262  to the DMA controller  281 . The DMA controller  281  reads out the pixel data stored in the FIFO  405 - 1  or FIFO  404 - 1  or the parity data correspondingly to the DMA command, and supplies it to the buffer controller  211  through the DMA bus  251 . The buffer controller  211  processes the data supplied through the DMA bus  251  to write it in the data buffer  212 . Thereby, for example, the pixel data and parity data are stored in the data buffer  212  as shown in  FIG. 42 . 
   The SCSI controller  202  receives supply of a command from the controller  262  through the control bus  252 , delivers a controls signal to the buffer controller  211  corresponding to the command, and reproduces the pixel data and the parity data stored in the data buffer  212  and takes it in. The SCSI controller  202  writes the data taken in from the data buffer  212  through the buffer controller  211  on the prescribed track of the corresponding prescribed hard disk  201 . As described herein above, the pixel data of 1 frame, which is divided into 4 subblocks, is recorded in different hard disks  201  for respective subblocks, for example, as shown in  FIG. 33 . The parity data corresponding to the pixel data of this frame is recorded in a different hard disk  201 . 
   Next, the operation in which an error of the data reproduced from the hard disk  201  is corrected and the corrected data is sent out is described with reference to  FIG. 49 . The controller  262  delivers a command to the SCSI controller  202  through the control bus  252  to reproduce the parity data corresponding to the pixel data of a prescribed frame recorded in the hard disk  201 . The reproduced data is written on the data buffer  212  from the SCSI controller  202  through the buffer controller  211 . The controller  262  indicates to the DMA controller  281  through the control bus  252  to perform DMA transfer of the data written in the data buffer  212  as described herein above to the RAID controller  282 . The DMA controller  281  reads out the data written on the data buffer  212  through the buffer controller  211  correspondingly to the command, and receives the transfer through the DMA bus  251 . The data is supplied to and stored in the FIFO  406 A- 1  and  406 B- 1  through the 64 bit bus. The data written on the FIFO  406 A- 1  and  406 B- 1  is supplied to the RAID controller  282  through the 32 bit bus. 
   The RAID controller  282  receives the data supplied from the FIFO  406 A- 1  and  406 B- 1  as described herein above at the input B of the selector  451 . 
   After the selector  451  receives a packet transfer block, for example, of number 0 as described herein above, the packet transfer block of number 0 is selected by the selector  451 , supplied to the delay element  401 - 4  as shown in  FIG. 49 , and supplied to the input A of the selectors  454  and  455  respectively. As shown in  FIG. 49 , because the selector  455  is controlled so as to select the input B, the data supplied to the input A is not supplied to the delay element  403 . Conversely, because the selector  454  is controlled so as to select the input A, the selector  454  selects the packet transfer block of number 0 and supplies it to the subsequent delay element  402  for holding. 
   Next, the packet transfer block of number 1 is entered to and selected by the selector  451  and supplied to the delay element  401 - 4 , when, the packet transfer block of number 0 which has been held in the delay element  401 - 4  is transferred to and held in the subsequent delay element  401 - 3 . 
   Further, the selector  454  calculates the exclusive OR of the packet transfer block of number 1 from the selector  451  supplied from the input A and the packet transfer block of number 0 held in the delay element  402 , and supplied it to the delay element  402  for storing. 
   Next, though the packet transfer block of number 3 would be entered if the packet transfer block of number 3 is normal, but it is assumed that the packet transfer block of number 3 happens to have an error, the DMA controller  281  selects the parity data instead of the packet transfer block of number 3, and the parity data is read out from the data buffer  212 , and supplied to the RAID controller  281 . The parity data is supplied from the selector  451  to the delay element  401 - 4 , and also supplied to the input A of the selector  454 . When the selector  454  calculates the exclusive OR of the data from the input A and the data from the input B, the input A receives the parity data, on the other hand, the delay element  402  receives the exclusive OR of the packet transfer block of number 0, the packet transfer block of number 1, and the parity data which is calculated by the selector  454  because the delay element  402  holds the exclusive OR of the packet transfer block of number 0 and the packet transfer block of number 1. 
   Further, when the packet transfer block of number 3 is entered from the selector  451 , the packet transfer block of number 3 is supplied to the delay element  401 - 4 , and the parity data which has been held in the delay element  401 - 4  is supplied to the subsequent delay element  401 - 3 . The packet transfer packet of number 1 which has been held in the delay element  401 - 3  up to that time is supplied to the subsequent delay element  401 - 2  for storing. The packet transfer block of number 0 which has been held in the delay element  401 - 2  up to that time is supplied to and held in the further subsequent delay element  401 - 1 . 
   The selector  454  calculates the exclusive OR of the packet transfer block of number 3 supplied from the selector  451  and the data which has been obtained by calculating the exclusive OR of the packet transfer block of number 0, the packet transfer block of number 1, and the parity data stored in the delay element  402 . The calculation result is, in the result, the data that the packet transfer block of number 2 is error-corrected, and this data is held in the delay element  402 . 
   Next, when the packet transfer block of number 4 is entered to the selector  451 , this packet transfer block of number 4 is selected, and held in the delay element  401 - 4 . The packet transfer block of number 3 which has been held in the delay element  401 - 4  is supplied to the subsequent delay element  401 - 3 . The parity data which has been held in the delay element  401 - 3  up to that time is supplied to and held in the subsequent delay element  401 - 2 . The packet transfer block of number 1 which has been held in the delay element  401 - 2  up to that time is supplied to and held in the subsequent delay element  401 - 1 . The packet transfer block of number 0 which has been held in the delay element  401 - 1  up to that time is supplied to the input A of the selector  453 , selected by the selector  453 , and delivered to the video processing section  283 . 
   Next, when the packet transfer block of number 5 is entered to the selector  451 , the same processing as described herein above is performed, the packet transfer block of number 1 which has been held in the delay element  401 - 1  up to that time is selected by the selector  453  and delivered. 
   Next, though it is now the timing for entering the packet transfer block of number 6 in the selector  451 , if an error is detected in the packet transfer block of number 6, the parity data is supplied to the selector  451  instead of the packet transfer block of number 6. As the result, the parity data is supplied to and held in the delay element  401 - 4 , and supplied to and held in the delay element  403  through the selector  455 . 
   The combination of the selector  454  and the delay element  402  and the combination of the selector  455  and the delay element  403  are used alternately at an interval of 1 frame (every 4 packet transfer blocks). Therefore, in the case that packet transfer blocks of number 0 to number 3 are supplied to the delay element  402  through the selector  454 , the next 1 frame data of packet transfer blocks of number 4 to number 8 is supplied to the delay element  403  through the selector  455 . In the same manner as the case of the selector  454 , when a packet transfer block of a new number is entered to the selector  455 , the selector  455  calculates a new exclusive OR of the packet transfer block of new number and the existing calculation result of the packet transfer block or the exclusive OR obtained up to that time which has been held in the delay element  403 , and the calculation result is supplied to and held in the delay element  403 . 
   Therefore, at the timing of entering of packet transfer blocks of number 4, number 5, and number 6 (parity data) to the selector  451 , the selector  455  calculates the exclusive OR of the parity data entered from the selector  451  and the calculation result of the existing exclusive OR of packet transfer blocks of number 4 and number 5 which has been held in the delay element  403  up to that time, and supplies it to and holds it in the delay element  403 . On the other hand, the delay element  402  is holding the error-corrected data (the packet transfer block of number 2) of the precedent field. 
   Further, at the timing of entering of the packet transfer block of number 6 to the selector  451 , the delay element  401 - 1  delivers the entered parity data instead of the packet transfer block of number 2 having an error. If it is selected and delivered by the selector  453  as it is, the parity data is delivered resultantly. To avoid it, the selector  453  is switched at the timing so as to select the data from the input B instead of the data from input A. The output of the selector  452  is supplied to the input B of the selector  453 , and the selector  452  selects and delivers the error-corrected packet transfer block of number  2  entered to the input A which has been held in the delay element  402 . As the result, the parity data is not delivered from the switch  453 , but the error-corrected packet transfer block of number 2 is delivered. 
   Similarly in the following, as shown in  FIG. 49 , at the timing of entering of the packet transfer block of number 10 to the selector  451 , though the parity data which has been entered from the delay element  401 - 1  instead of the error-containing packet transfer block of number  6 , when, the selector  453  is switched to the input B side, the error-corrected packet transfer block is delivered from the selector  453  because the selector  452  selects the error-corrected packet transfer block of number 6 supplied to the input B which has been held in the delay element  403 . 
   As described herein above, when reproduction data is entered from the DMA controller  281  sequentially, errors are corrected sequentially in real time and corrected data is supplied to the video processing section  283 . 
   Next, the operation for recording in the disk recorder  2  shown in  FIG. 7  is summarized as described herein under. It is assumed that the video data supplied from the editing system  1  to the disk recorder  2  is the NTSC video data. 
   When the controller  262  of the disk recorder  2  receives a recording command from the host personal computer  3  through the SCSI, the controller  262  searches a free area which is recordable of the video data supplied from the editing system  1  with reference to the allocation map  303  on the RAM  263 . The free area searching is performed on the respective subblocks, each subblock is formed by dividing 1 frame video data into 4, and the parity data formed from these pixel data. At this time point, because the exact number of parity sectors and the number of sectors of 4 subblocks are unknown, the free area searching is performed not in sector unit but in track unit. 
   Based on the state of the searched free area, the controller  262  determines the recording position on the hard disk where the parity data and the data of 4 subblocks are to be recorded. The recording position is specified by the disk ID of the hard disk  201  and the start logical sector number of the sector from which the recording starts. In detail as shown in  FIG. 15 , the logical sector number  0  (sector of the outermost track) of the hard disk  201 - 1  having disk ID of 1 is the recording start position of the parity data. The logical sector number 599600 (sector of the innermost track) of the hard disk  201 - 2  having disk ID of 2 is the recording start position of the first subblock data. Further, the logical sector number  0  (sector of the outermost track) of the hard disk  201 - 3  having disk ID of 3 is the recording start position of the second subblock data. The logical sector number 599600 (sector of the innermost track) of the hard disk  201 - 4  having disk ID of 4 is the recording start position of the third subblock data. The logical sector number  0  (sector of the outermost track) of the hard disk  201 - 5  having disk ID of 5 is the recording start position of the fourth subblock data. 
   The controller  262  subsequently determines the physical address comprising the cylinder address, medium number, and sector number from the start logical sector number determined as the recording position of the data with reference to the physical address table  302 . 
   Further, the controller  262  determines with reference to the ZBR table  301  what zone out of 12 zones contains the cylinder address determined with reference to the physical address table  302 , and determines the number of sectors used in 1 track depending on the determined zone. 
   Further, the controller  262  generates a block map  304  based on the disk ID, logical sector number, number of sectors of the parity data, and the disk ID, logical sector number, and number of sectors of the first to fourth subblocks. 
   As described herein above, the block map corresponding to the video data allocated to the first frame (the frame having the number of 1) is formed. 
   Next, the controller  262  generates a sequence program to be supplied to the DMA controller  281  and the RAID controller  282  with reference to the block map  304 . The sequence program consists of the operand including the address for indicating the storing position on the data buffer  212  of the parity data and video data, the number of loops of packet transfer of the parity data and video data, and the command for indicating the RAID ratio as described with reference to  FIG. 41 . 
   The controller  262  transfers the command part out of the sequence program to the FIFO  407  through the control bus  252 . The RAID controller  282  detects the ratio of video data to parity data (RAID ratio) and the number of transfer loops (transfer loop period) with reference to the command supplied through the FIFO  407 . In detail, the RAID controller  282  receives the command, and detects thereby the RAID ratio for parity formation and the number of repetition of the process based on the video data supplied from the video processing section  283 . 
   The RAID controller  282  calculates the parity data from 4 packet transfer blocks (subblock) when the RAID ratio is 4:1, and calculates the parity data from 2 packet transfer blocks (subblock) when the RAID ratio is 2:1. 
   The calculated parity data is supplied to the FIFO  404  every word and the pixel data is supplied to the FIFO  405  every word. 
   On the other hand, the controller  262  supplies the DMA command ( FIG. 41 ) which indicates the position in the data buffer  212  where the subblock of the supplied video data should be stored to the FIFO  501  in the controller  281 . The DMA controller  281  DMA-transfers the parity data stored in the FIFO  404  and the pixel data stored in the FIFO  405  to the position on the data buffer  212  indicated by the address written in the operand of the DMA command stored in the FIFO  501  every 1 packet transfer block (=128 words). The transfer operation is repeated the number of times corresponding to the number of loops written in the DMA command. 
     FIG. 50  schematically shows the size of 4 subblocks and 1 parity data of the frame having the number of 1 in  FIG. 15 . As shown in  FIG. 50 , the size of the first subblock S 1 - 1  is 393 sectors, the size of the second subblock S 1 - 2  is 567 sectors, the size of the third subblock S 1 - 3  is 393 sectors, and the size of fourth subblock S 1 - 4  is 567 sectors. The size of the parity data is set to 567 sectors corresponding to the maximum size out of sizes of the first to fourth subblocks. 
   It is assumed that the data of 128 words is recorded in 1 sector, then the data quantity of the first subblock is 50304 words (=393 sectors×128 words), and the data quantity of the second subblock is 72576 words (=567 sectors×128 words). The size of the fourth subblock and the parity data is same as that of the second subblock, and the size of the third subblock is same as that of the first subblock. 
   As described with reference to  FIG. 43  and  FIG. 44 , the pixel data of these 4 subblocks is not the 4 subblocks that are formed by dividing continuous pixels which constitute 1 frame image, but the 4 subblocks that are formed by collecting a prescribed number of data in 128 words (packet transfer block) unit which are distributed at the prescribed positions on 1 image. 
   In the case of the example shown in  FIG. 50 , 4:1 RAID is performed in the range T 1  of 393 sectors from the left in  FIG. 50 , and on the other hand, 2:1 RAID is performed in the range T 2  on the right hand of the range T 1 . The number of transfer (number of loops) in the range T 1  is prescribed to be 393 times and the number of loops in the range T 2  is prescribed to be 174 (=567−393), 1 frame image data is thereby transferred to the data buffer  212 . 
   In this case of the example, because 4:1 RAID and 2:1 RAID are required, the DMA command for 4:1 RAID transfer in the range T 1  and the DMA command for 2:1 RAID transfer in the range T 2  are necessary. 
   As described herein above, in the RAID controller  282 , because the parity data is generated sequentially correspondingly to the input pixel data, when packet transfer blocks of respective 4 subblock is entered sequentially, the packet blocks are delivered sequentially to the data buffer  212 , and corresponding parity data is generated sequentially one parity data per RAID ratio, and delivered to the data buffer  212 . 
   In the range T 1 , transfer is performed correspondingly to the DMA command which indicates 4:1 RAID. In this case, the video data (50304 word pixel data) of 393 packet transfer blocks of the first to fourth subblock is DMA-transferred to and written in the second to fifth addresses of the data buffer  201  corresponding to the hard disks  201 - 2  to  201 - 5  having disk ID of 2 to 5. Further, the parity data (50304 word parity data) of 393 packet transfer blocks is stored in the first address of the data buffer  212  corresponding to the hard disk  201 - 1  having disk ID of 1 by way of 393 loop transfers. 
   Next, the DMA controller  281  writes the pixel data of 174 sectors corresponding to the range T 2  of the second subblock in the seventh address (the address next to the area where the pixel data of 393 sectors of the second subblock in the range T 1  is recorded) of the hard disk  201 - 3  having disk ID of 3 by way of 174 loop transfers correspondingly to the DMA command of 2:1 RAID. Further similarly, the DMA controller  281  transfers to and writes in the eighth address (the address next to the area where the video data of 393 sectors of the fourth subblock in the range T 1  is recorded) of the data buffer  212  corresponding to the hard disk  201 - 5  having hard disk ID of 5 byway of 174 loop transfers. Further, the parity data (22272 word parity data) of the 174 packet transfer blocks is written in the sixth address (the address next to the area where the parity data of 393 sectors in the range T 1  is recorded) corresponding to the hard disk  201  having disk ID of 1. 
   As described herein above, the video data of the frame having the number of 1 shown in  FIG. 15  is transferred to and stored in the data buffer  212 . Similarly in the following, the video data of the number 2, 3, . . . is transferred sequentially to the data buffer  212  for buffering. 
     FIG. 50  shows an example of the case in which the parity data is recorded on the track in the zone  1  having 567 sectors per outermost circumferential 1 track of the ZBR table shown in  FIG. 9 , and the track in the zone  12  having 393 sectors per innermost circumferential 1 track. In detail, for example, the parity data of 567 sectors is recorded on the track of the outermost circumferential zone  1  of the hard disk  201 - 1 , the first subblock data of 393 sectors out of subblocks is recorded on the track of the innermost circumferential zone 12 of the hard disk  201 - 2 , the second subblock data of 567 sectors is recorded on the track of the outermost zone  1  of the hard disk  201 - 3 , the third subblock data of 393 sectors is recorded on the track of the innermost circumferential zone 12 of the hard disk  201 - 4 , and the fourth subblock data of 567 sectors is recorded on the track of the outermost circumferential zone  1  of the hard disk  201 - 5 . 
   As described herein above, the track of the outermost circumference and the track of the innermost circumference are used in the form of pair. Therefore, for example, when the pair consisting of the zone  1  and zone  12  becomes full and can not be used more, the zone  2  having 544 sectors per 1 track positioned at the second outermost circumference next to the zone  1 , and the zone  11  having 416 sectors per 1 track positioned at the second innermost circumference next to the zone  12  are used in the form of a pair. 
     FIG. 51  shows an exemplary structure of the parity data and subblock data in this case. In this example, the parity data of 544 sectors is recorded, for example, on the track in the second outermost circumferential zone  2  of the hard disk  201 - 2 , the first subblock data of 416 sectors out of subblocks is recorded on the track having 416 sectors per 1 track positioned second from the innermost circumference of the hard disk  201 - 3 , the third subblock data of 416 sectors is recorded on the track in the zone  11  of the hard disk  201 - 5 , and the fourth subblock data of 544 sectors is recorded on the track in the zone  2  of the hard disk  201 - 6 . In this case, 4:1 RAID is performed in the range T 1  of 416 sectors from the left side in the figure, on the other hand, 2:1 RAID is performed in the range T 2  of following 128 sectors. 
   Similarly in the following,  FIG. 52  to  FIG. 55  show examples of cases in which the zone  3  and zone  10  is used as a pair, the zone  4  and the zone  9  are used as a pair, the zone  5  and zone  8  are used as a pair, and the zone  6  and the zone 7 are used as a pair respectively. 
   As described herein above, by using the outer circumference zone and the inner circumference zone as a pair, with addressing on one hard disk  201 , the size of each subblock can be set so that the gap θgap value of the respective subblock is approximately equal each other, the time necessary to read out and write each subblock is approximately equal. 
   The above-mentioned structure shown in  FIG. 50  to  FIG. 55  is the case of NTSC video data, but in the case of PAL video data, the size of the parity data and subblock is set as shown in  FIG. 56  to  FIG. 61 . In the case of PAL video data, the number of pixels for 1 frame is 1440×612, which is more than that in the case of NTSC video data, and the number of sectors per 1 track in each zone is specified as shown in  FIG. 10 .  FIG. 56  to  FIG. 61  respectively show the case in which the zone  1  and zone  12  shown in  FIG. 10  are used as a pair, the case in which the zone  2  and the zone  11  are used as a pair, the case in which the zone  3  and the zone  10  are used as a pair, the case in which the zone  4  and the zone  9  are used as a pair, the case in which the zone  5  and the zone  8  are used as a pair, and the case in which the zone  6  and the zone  7  are used as a pair. 
   In the setting example shown in  FIG. 56 , the parity of 561 sectors is recorded on the outermost circumferential track in the zone  1  of the first hard disk  201 , the first subblock data out of subblocks of 391 sectors is recorded on the innermost circumferential rack in the zone  12  of the second hard disk, the second subblock data of 561 sectors is recorded on the track in the zone  1  of the third hard disk, the third subblock data of 391 sectors is recorded on the track in the zone  12  of the fourth hard disk, the fourth subblock data of 561 sectors is recorded on the track in the zone  1  of the fifth hard disk, and the fifth subblock of 391 sectors is recorded on the innermost circumferential track in the zone  12  of the sixth hard disk. The data of 391 sectors in the range T 1  from the left side in the figure is transferred by way of 5:1 RAID, and the data of 170 sectors on the right hand of the range T 1  is transferred by way of 2:1 RAID. In this case, the size of 1 packet transfer block is 128 words. Therefore, the 391 transfer loops are in the range T 1  and the 170 transfer loops are in the range T 2 . 
   In the examples shown  FIG. 57  to  FIG. 61 , only the number of transfer loops is different from that shown in  FIG. 56 , and other operations are the same as those shown in  FIG. 56 . 
   As described in the step S 12 - 8  of the flow chart shown in  FIG. 26 , for example, when the parity data and subblock data of 1 frame are stored in the data buffer  212 , the parity data and subblock data of 1 frame are transferred directly to the hard disk  201 , but, for example, when the parity data and subblock data of 10 frames are stored in the data buffer  212 , the controller  262  schedules the order of data transfer according to SCAN algorithm. 
   For example, it is assumed that the number of hard disk  201  is  6  and the data is recorded as shown in  FIG. 62 , then the data buffered in the third address which indicates the place where the data to be transferred to the hard disk  201  having disk ID of 3 is held is the second subblock data S 1 - 2  of the frame of the number 1, the first subblock data S 2 - 1  of the frame of the number 2, the parity data P 3  of the frame of the number 3, the fourth subblock data S 5 - 4  of the frame of the number 5, the third subblock data S 6 - 3  of the frame of the number 6, the second subblock data S 7 - 2  of the frame of the number 7, the first subblock data S 8 - 1  of the frame of the number 8, and the parity data P 9  of the frame of the number 9. 
   The subblock data S 1 - 2  is disposed on the outer circumference, the subblock data S 2 - 1  is disposed on the inner circumference, the parity data P 3  is disposed on the outer circumference, the subblock data S 5 - 4  is disposed on the outer circumference, the subblock data S 6 - 3  is disposed on the inner circumference, the subblock data S 7 - 2  is disposed on the outer circumference, the subblock data S 8 - 1  is disposed on the inner circumference, and the parity data P 9  is disposed on the outer circumference. Therefore, if these data are recorded in the order from S 1 - 2 , to S 2 - 1 , P 3 , S 5 - 4 , S 6 - 3 , S 7 - 2 , S 8 - 1 , and P 9 , the head of the hard disk having disk ID of 3 reciprocates between the outer circumference and the inner circumference of the hard disk, the reciprocation causes delayed access. 
   To avoid such delay, the controller  262  schedules the transfer of the video data from the frame of number 1 to the frame of number 10 so that the plurality of data is transferred to the disk  201  in the order from the data disposed on the outermost circumference with reference to the block map  304  ( FIG. 15 ) formed respectively. In detail, the data are arranged in the order from the data recorded on the outermost circumference with reference to the block map  304  shown in  FIG. 15 , then the data is arranged in the order S 1 - 2 , P 3  S 5 - 4 , S 7 - 2 , P 9 , S 8 - 1 , S 6 - 3 , and S 2 - 1 . By scheduling the order of the data arrangement as described herein above, the controller  262  suppresses the head migration distance for recording to the minimum to improve the access speed. 
   When the data recorded in the hard disk  201  as described herein above is reproduced, the operation reverse to the recording is performed. The operation is summarized as described herein under. 
   When the controller  262  receives an command of reproduction of one or more frames from the host personal computer  3 , the controller  262  reads the start logical sector of the frame of the number which is indicated to be reproduced with reference to the block map  304 , and determines the physical address corresponding to the logical sector with reference to the physical address table  302 . The controller  262  requests the buffer controller  211  through the control bus  252  to take an access to the determined physical address. The buffer controller  211  controls the SCSI controller  202  to reproduce the data from the address specified by the physical address of the hard disk  201  in response to the request. The reproduction data is supplied from the SCSI controller  202  to the buffer controller  211 , and written in the data buffer  212 . 
   In this case also, the controller  262  waits until reproduction request of 10 frames is accumulated as described herein above, when the controller  262  accepts reproduction request of 10 frames, the controller  262  schedules the order so that the head migration distance is suppressed to the minimum, and requests the buffer controller  212  to reproduce the image data of 10 frames according to this schedule. 
   The controller  262  generates a sequence program for DMA transfer of the data stored in the data buffer  212  to the RAID controller  282  with reference to the block map  304 . This sequence program supplied to the FIFO  501  of the DMA controller  281  through the control bus  252 . The sequence program (DMA command) specifies the address of the data buffer  212  on the operand as described herein above, and also the number of loops are specified on the command. The DMA controller  281  reads out the data written in the data buffer  212  correspondingly to the command, and receives it through the DMA bus  251 , and transfers it to the RAID controller  282 . 
   The RAID controller  282  corrects the input data sequentially in real time as described herein above. 
   The error-corrected video data output from the RAID controller is supplied to the video processing section  283 , and the clock is changed to a clock of a lower frequency. The data output from the video processing section  283  is supplied from the input-output controller  284  to the matrix switcher section  21  of the editing system  1  through the SDI. 
   The matrix switcher section  21  indicates the output processor  32 - 2  to convert the video data entered from the prescribed channel of the SDI to the video signal of SDI format, and to delivers to the main monitor  4  for displaying. Thus a user can view an image recorded in the hard disk  201 . 
   When a prescribed indication is entered from the host personal computer  3 , the matrix switcher section  21  of the editing system  1  supplies the video data taken in from the disk recorder  2  to the video processing section  22 . In the video processing section  22 , the demultiplexer circuit  41 - 1  takes in a key signal contained in the input video packet of SDI format, and delivers it to the key signal processing circuit  51 - 1 . The demultiplexer circuit  41 - 2  delivers the video signal component taken out from the input video packet of SDI format to the video signal processing circuit  51 - 2 . 
   When a user controls the host personal computer  3  to enter a prescribed command, the control block  45  of the video processing section  22  receives the command from the host personal computer  3  through the control bus  25 , and controls the wipe signal generating circuit  52 - 1  correspondingly to this command. The wipe signal generating circuit  52 - 1  generates a wipe signal corresponding to the command from the control block  45 , and supplies the wipe signal to the key signal processing circuit  51 - 1  and the video signal processing circuit  51 - 2 . The key signal processing circuit  51 - 1  and the video signal processing circuit  51 - 2  process the key signal and the video signal correspondingly to the wipe signal entered from the wipe signal generating circuit  52 - 1  and delivers it to the mix circuit  71 - 2 . 
   Also the demultiplexer circuit  41 - 3  and demultiplexer circuit  41 - 4  extract a key signal and video signal of another channel in the same manner as the demultiplexer circuits  41 - 1  and demultiplexer circuit  412 , and respectively delivers to the key signal processing circuit  51 - 3  and the video signal processing circuit  51 - 4 . The wipe signal generating circuit  52 - 2  generates a wipe signal correspondingly to the command from the control block  45 , and delivers it to the key signal processing circuit  51 - 3  and the video signal processing circuit  51 - 4 . The key signal processing circuit  51 - 3  and the video signal processing circuit  51 - 4  process the key signal and video signal correspondingly to the wipe signal entered from the wipe signal generating circuit  52 - 2 , and respectively deliver to the frame memory  61 - 1  and frame memory  61 - 2 . 
   The three dimensional address generation circuit  63  receives the command from the host personal computer  3  through the control block  45 , and delivers a three dimensional address coordinate corresponding to this command to the frame memory  61 - 1  and frame memory  61 - 2 . As the result, the key signal and video signal which are converted to the three dimensional coordinate respectively are read out from the frame memory  61 - 1  and the frame memory  61 - 2 , and supplied respectively to the interpolator  62 - 1  and the interpolator  62 - 2 . The interpolator  62 - 1  and the interpolator  62 - 2  perform interpolation respectively on the input key signal and video signal correspondingly to the three dimensional coordinate address from the three dimensional address generation circuit  63 , and deliver to the mix circuit  71 - 2 . 
   The background video signal which the demultiplexer circuit  41 - 5  has extracted from the prescribed input of the matrix switcher section  21  is supplied to the mix circuit  71 - 1 . The mix circuit  71 - 1  mixes the video signal which has been subjected to special effect delivered from the interpolators  62 - 1  and  62 - 2  with the background video signal delivered from the demultiplexer circuit  41 - 5  properly, and delivers the mixed video signal to the mix circuit  71 - 2 . The mix circuit  71 - 2  mixes the output from the mix circuit  71 - 1  with the output of the key signal processing circuit  51 - 1  for processing a key signal which has been subjected to transition effect and the output of the video signal processing circuit  51 - 2  properly, and delivers the mixed video signal. 
   The output of the mix circuit  71 - 2  and the mix circuit  71 - 1  is supplied to the matrix switcher section  21 . 
   When a prescribed command is entered from the host personal computer  3  in the matrix switcher section  21 , the video signal processed in the video processing section  22  is selected properly, and supplies to any one of output processors  32 - 3  to  32 - 12 , further supplied from any one of the combiners  33 - 1  to  33 - 10  to the disk recorder  2 , and written in the hard disk  201 . 
   On the other hand, in the case that the audio signal has been entered to the matrix switcher section  21 , the control block  34  selects it properly, and supplies it to the audio processing section  23 . In the audio processing section  23 , the separators  81 - 1  to  81 - 3  separate the embedded audio signal from the input SDI signal, and supplies it to the mixer block  83 . In the mixer block  83 , the control block  86  adjusts the variable resistors  91 - 1  to  91 - 6  to a prescribed value properly corresponding to the command from the host personal computer  3 . As the result, the audio signal separated by the separators  81 - 1  to  81 - 3  is adjusted to a prescribed level, and supplied subsequently and added to the adder  92 - 1  or the adder  92 - 2 . 
   The audio signal delivered from the adder  92 - 1  or the adder  92 - 2  is entered to the embedded circuit  85 , subjected to time axis compression, and converted to an embedded audio signal, and subsequently supplied to any prescribed one of the combiners  33 - 1  to  33 - 10  of the matrix switcher section  21 . The combiners  33 - 1  to  33 - 10  superimpose the input audio signal on the vertical return segment of the input video signal, supply it to the disk recorder  2 , and the superimposed signal is recorded in the hard disk  201 . 
   The audio signal delivered from the adder  92 - 1  or the adder  92 - 2  of the mixer block  83  comes out from the speaker  6  through the amplifier  5 . 
   The video data processed in the editing system is supplied properly from the output processor  32 - 1  to the host personal computer  3 . 
   In this disk recorder  2 , because high speed access is possible, it is possible that the multi-channel video data is reproduced simultaneously from the hard disk  201  and processed simultaneously in the video block  271 . Therefore, it is also possible that the video data of a plurality of channels reproduced simultaneously from the hard disk  201  is synthesized to form a synthesized image of 1 channel. 
   Further as shown in  FIG. 63 , it is assumed that, for example, the stream A, stream B, and stream C are respectively reproduced from the source VTR  9  and recorded. The stream A consists of the frame A 1  to frame A 5  which are continuous in the time, the stream  2  consists of the frame B 1  to frame B 5  which are continuous in the time, and the stream  3  consists of the frame C 1  to frame C 5  which are continuous in the time. These frame A 1  to frame A 5 , frame B 1  to frame B 5 , and frame C 1  to frame C 5  are streams which are to be reproduced in the order of suffix numbers. 
   In the state that the stream A to stream C is stored in the hard disk  201 , when the host personal computer  3  specifies these respective frames in frame unit in the order of, for example, the frame A 4  of the stream A, the frame B 1  of the stream B, the frame A 1  of the stream A, and the frames C 3  and C 1  of the stream C, the respective frames are reproduced in the order in real time, and delivered to the main monitor  4  for displaying. In this case, the streams of the frame A 4 , B 1 , A 1 , C 3 , and C 1  are not recorded actually in the hard disk  201 , but merely the order of frames to be reproduced is specified on the host personal computer  3  side. In detail, when a data string of the frame corresponding to the stream  1  is supplied from the host computer  3  to the controller  262  of the CPU block  261  of the disk recorder  2 , the controller  262  stores it in the RAM  263 . The controller  262  of the CPU block  261  sequentially reads out the image data of the respective frames from the hard disk  201  in the order corresponding to the data string stored in the RAM  263  and reproduce it. 
   Similarly, as shown in  FIG. 63 , merely by performing the process that the host personal computer  3  specifies the data string of frames B 3 , B 2 , C 1 , A 1 , and A 2  and the data string is transferred to the disk recorder  2  and stored in the RAM  263 , the stream corresponding to the stored data string is read out from the hard disk  201  as the stream  2  and reproduced. In the case that a plurality of monitors are used for monitoring, the stream  1  and stream  2  are delivered simultaneously to respective monitors for displaying. 
   Next, the detailed structure of the audio block  231  of the disk recorder  2  to which the audio signal is supplied is described with reference to  FIG. 64  herein under. The DMA controller  241  supplies an audio signal supplied from the FIFO  502  to the buffer controller  211 - 8  through the DMA bus  251  for DMA-transferring it to the corresponding data buffer  212 - 8 , and reads the audio signal read out from the data buffer  212 - 8  though the DMA bus and supplies it to the FIFO  501 . 
   The FIFO  501  delivers the audio signal supplied from the DMA controller  241  to any FIFO of the FIFO&#39;s  504 - 1  to  504 - 24  based on the command supplied from the controller  262  to the FIFO  503  through the control bus  252 . The FIFO  504  supplies the audio signal entered from the FIFO&#39;s  505 - 1  to  505 - 24  to the DMA controller  241 . 
   The FIFO  504 -i, FIFO  505 -i, channel DSP  506 -i, ring buffer  507 -i, and interface (I/F)  508 -i (i=1, 2, . . . ) constitutes one slot module having audio signal recording/reproducing function. Therefore, there is a 24 channel slot module in the audio block  231 . The operation of the slot module will be described with reference to  FIG. 66  hereinafter. 
   The channel DSP  506 -i stores the audio signal supplied from the FIFO  504 -i in the ring buffer  507 -i, reproduces and fades the data, and delivers it to the interface  508 -i. The channel DSP  506 -i stores the audio signal supplied from the interface  508 -i in the ring buffer  507 -i, reproduces the data, and delivers it to the FIFO  505 -i. The interface  508 -i delivers the audio signal reproduced from the ring buffer  507 -i to the fixed speed reproduction system namely normal bus  514  and the variable speed reproduction system namely variable bus  515 . 
   The cross fade DSP  513  controls the parallel mixers  509 - 1  and  509 - 2  to cross-fade 24 reproduction signals entered from respective slot modules through the normal bus  514 , and to deliver the synthesis signal of 8 channels. Each of the synthesis signals O 0  to O 15  is added with reproduction signals I 0  to I 23  for 24 channels which are multiplied by coefficients K i (K i =0 or 1) as shown in the following equation (13).
 
 O   n   =K   0   I   0   +K   1   I   1   + . . . +K   23   I   23 ( n= 0 to 15)  (13)
 
   The variable speed reproduction processor  510  synthesizes the reproduction signal of 24 channels entered through the variable bus  515  to form the synthesis signal of 4 channels in the same manner as the parallel mixer  509 , and performs varying-speed (program play) processing such as expansion or compression of the time axis and delivers it. The musical interval of reproduction signal delivered from the variable speed reproduction processor  510  is changed and kept constant regardless of the degree of varying-speed reproduction. 
   Because the parallel mixers  509 - 1  and  509 - 2  and the variable speed reproduction processor  510  operate independently, it is possible to process the reproduction signal supplied from the same slot module using the parallel mixers  509 - 1  and  509 - 2  and variable speed reproduction processor  510 . 
   The router DSP  511  implements compensation of delay due to the difference in process time between the parallel mixer  509  and the variable speed reproduction processor  510  based on the program recorded in the RAM  512 , and delivers the signal of 16 channels out of the 20 channels which is the total of the signal of 16 channels delivered from the parallel mixer  509  (fixed speed reproduction system) and the signal of 4 channels delivered from the variable speed reproduction processor  510  (variable speed reproduction system) to the input-output (I/O) controller  242  according to the command from the controller  262 . 
   In this embodiment, while the audio signal is reproducing, a part of the audio signal is rewritten synchronously with the sound. In detail, as shown in  FIG. 65A , the audio signal which contains a part A to be modified (replaced) is reproduced, at the timing of reproduction of the part A to be modified, the input of data B for replacing is received as shown in  FIG. 65B , and the data B to be placed on the position where the part A to be modified is recorded as shown in  FIG. 65C . 
     FIG. 66  shows the partial structure for performing such process, which corresponds to the structure of the audio block  231  shown in  FIG. 64  mainly. 
   A reference signal generator  601  generates a reference signal and supplies it to a reproduction ring buffer  603  and a recording ring buffer  611 . The frequency of the reference signal is arbitrary, and only the simultaneity is required. The reference signal generator  601  is equivalent to the controller  262 , and in this embodiment, generates reference signals every 1 frame period of the video signal. Such operation allows the reference signal generator  601  to generate the proper reference signal even if the video signal is changed from the normal reproduction to variable speed reproduction (program play). 
   A bus controller  602  is equivalent to the DMA controller  241 , reads out the audio signal from the hard disk  201  through the DMA bus  251 , and transfers it to the reproduction buffer  603 . Transfer is discontinuous temporally. 
   The reproduction ring buffer  603  and recording ring buffer  611  are independent buffers each other logically, and are under address management in the form of a ring. However, the reproduction ring buffer  603  and the recording ring buffer  611  are combined physically, and equivalent to the ring buffer  507 . The reproduction ring buffer  603  records the transferred data in the address specified by the bus controller  602 , and delivers the address for indicating the timing when a reference signal is supplied from the reference signal generator  601  to a memory controller  604 . 
   The memory controller  604  reproduces the discontinuous data recorded in the reproduction ring buffer  603  using the clock of fixed frequency of 48 kHz, and delivers it to a reproduction signal processor  605  as the continuous signal. The reproduction signal processor  605  performs prescribed processing such as level calculation, interpolation processing for variable speed reproduction, and frequency characteristic change on the continuous signal, and delivers it to a cross fader  607 . The memory controller  604  and the reproduction signal processor  605  are equivalent to the channel DSP  506 . 
   The cross fader  607  is equivalent to the cross fader DSP  513 , and switches any one of the reproduction signal from the reproduction signal processor  605  and the digital input signal from a digital input section  606  (equivalent to the input-output controller  242 ), and delivers the signal to the subsequent sections. When the cross fader  607  is switched to the reproduction signal side, the reproduction signal delivered from the reproduction signal processor  605  is delivered to the subsequent stage, on the other hand, when the cross fader  607  is switched to the digital input signal side, the digital input signal delivered from the digital input section  606  is delivered to the subsequent stage, and during switching transition, the reproduction signal and digital signal are faded in or faded out and synthesized, and delivered to the subsequent stage. 
   The output signal from the cross fader  607  is delivered from a digital output section  609  (equivalent to the input-output controller  242 ) to the outside of the apparatus for monitoring, and delivered to a recording signal processor  608 , in which subjected to processing such as level change and frequency characteristic change, and delivered to a memory controller  610 . The memory controller  610  stores the signal continuously in the arbitrary address of the recording ring buffer  611 . The recording signal processor  608  and the memory controller  610  are equivalent to the channel DSP  506 . 
   The recording ring buffer  611  delivers the address which indicates the timing when the reference signal is supplied from the reference signal generator  601  to the memory controller  610 . 
   The audio signal to be recorded in the reproduction ring buffer  603  and the recording ring buffer  611  is generally managed in the form of block having arbitrary data size, and the signal reproduced from these buffers  603  and  611  is managed in block unit. In this embodiment, 1 block is composed of 128 k byte audio signal corresponding to 10 frame video signal. 
   For example as shown in  FIG. 68 , in the case that the signal is switched to the digital input signal entered from the digital input section  606  in the middle of the block B 2  of the reproduction signal reproduced from the reproduction ring buffer  603  and recorded in the recording buffer  611 , the reproduction signal is faded out and the digital input signal is faded in as described herein above as the output from the cross fader  607 . The timing when the output signal (recording signal) is recorded in the recording ring buffer  611  delays from the reproduction signal due to processing in the memory controller  604 , reproduction signal processor  605 , cross fader  607 , recording signal processor  608 , and memory controller  610 . 
   If the recording signal is segmented in block unit at the quite same phase as that of block segment of the reproduction signal when the recording signal is re-segmented into block unit, blocks B 2 , B 3  of the original reproduction signal are replaced with overwrite blocks WB  2  and WB 3 , and the capacity of the hard disk  201  can be utilized usefully. In the case that overwrite blocks WB 2  and WB 3  are not overwritten on the blocks B 2  and B 3  and recorded on other area, the order of reproduction may be simply B 1 , WB 2 , and WB 3 . 
   To segment the recording signal into block unit in the quite same phase as the segment block of the reproduction signal, it is required to know the head address of the recording block (overwrite block WB 2 ) in the recording ring buffer  611  correctly. 
   Processing to know the head address of the recording block is described with reference to a flow chart shown in  FIG. 69 . In the step S 101 , the head address of the block B 2  in the reproduction ring buffer  603  and the position (PB_REF) of the reproduction ring buffer  603  located when the reference signal is supplied are read out by the memory controller  604 , and delivered to the controller  262 . When, the memory controller  610  delivers the position (REC_REF) of the recording ring buffer  611  corresponding to the same reference signal to the controller  262 . 
   In the step S 102 , the controller  262  calculates the address quantity (signal processing delay) resultant from the rotation of the recording buffer  611  while the reproduction signal from the reproduction ring buffer  603  is processed in the memory controller  604 , the reproduction signal processor  605 , the cross fader  607 , the recording signal processor  608 , and the memory controller  610 . 
   In the step S 103 , the controller  262  adds the signal processing delay to the head address of the reproduction block in the reproduction ring buffer  603 , and further adds the difference (REC_REF-PB_REF) between the position (PB_REF) of the reproduction ring buffer  603  and the position (REC_REF) of the recording ring buffer  611  obtained when the same reference signal is supplied, and the head address of the recording signal block is thereby calculated.
 
recording block head address=reproduction block head address+signal processing delay+ REC   —   REF−PB   —   REF   (14)
 
   For example, as shown in  FIG. 70 , in the diagram in which addresses of the reproduction ring buffer  603  and the recording ring buffer  611  are represented by the rotation angle from the arbitrary reference position respectively, the reproduction block head address is 45 degrees, PB_REF is 90 degrees, and REC_REF is 150 degrees. If the signal processing delay is 75 degrees, it gives the recording reproduction block head address of 180 degrees (=45+75+150−90), and the calculation result indicates the position at 180 degrees from the arbitrary reference position of the recording ring buffer  611 . 
   The controller  262  stores this recording block head address, and DMA-transfers the data recorded in the recording block head address first, which has been calculated and stored, to the DMA bus  251  through the bus controller  612  when the recording block data (overwrite block WB 2 ) is recorded on the hard disk  201 . 
   The description returns to  FIG. 66 . The bus controller  612  reads the signal recorded on the recording ring buffer  611  as a discontinuous burst data, and delivers it to the DMA bus  251 . This data is recorded on the hard disk  201 . 
     FIG. 71  shows a structure comprising a plurality of reproduction signal blocks shown in  FIG. 66  (bus controller  602 , reproduction ring buffer  603 , memory controller  604 , and reproduction processor  605 ) and a plurality of recording signal blocks (recording signal processor  608 , digital output section  609 , memory controller  610 , recording ring buffer  611 , and bus controller  612 ) shown in  FIG. 66 , added with a path changing section  621 . In  FIG. 71 , two reproduction ring buffers  603 - 1  and  603 - 2  and two recording ring buffers  611 - 1  and  611 - 2  are shown, however, there are 24 buffers respectively. 
   The path changing section  621  is equivalent to the router DSP  511 , and supplies the reproduction signal from the reproduction signal processors  605 - 1  and  605 - 2  to the arbitrary input of a multi-cross fader  622  which is connected to the recording signal processor  608 - 1  or recording signal processor  608 - 2 . The multi-cross fader  622  mixes the input reproduction signal with the digital input signal entered from the digital input sections  606 - 1  and  606 - 2  gradually, and delivers the mixed signal to the recording processors  608 - 1  and  608 - 2 . The number of inputs and the number of outputs of the path changing section  621  are not necessarily equal, for example, it is possible that the output of both reproduction ring buffers  603 - 1  and  603 - 2  is supplied to the recording signal processor  608 - 1  and recorded on the recording ring buffer  611 - 1 . 
   For example, the recording block head address  2  in the recording buffer  611 - 2  at the time when the reproduction signal reproduced from the reproduction ring buffer  603 - 1  is recorded on the recording ring buffer  611 - 2  is calculated from the following equation (15).
 
recording block head address 2=reproduction block head address 1+signal processing delay+ REC   —   REF 2 −PB   —   REF 1   (15)
 
REC_REF  2  is the address of the recording ring buffer  611 - 2  corresponding to the reference signal, and PB_REF  1  is the address of the reproduction ring buffer  603 - 1  corresponding to the same reference signal. Further, the reproduction block head address 1 is the head address of the reproduction block of the reproduction ring buffer  603 - 1 .
 
   As described herein above, by introducing the path changing section  621 , the reproduction ring buffers  603 - 1  and  603 - 2  and the recording ring buffers  611 - 1  and  611 - 2  are used in any arbitrary combination, and the independence of the reproduction signal block and the recording signal block is improved. 
     FIG. 72  is the structure which is structured by adding a reproduction signal synthesizing section  631  to the structure shown in  FIG. 71 , the reproduction signal synthesizing section  631  is equivalent to the parallel mixer  509  which is controlled by the router DSP  511 . The reproduction signal synthesizing section  631  synthesizes the reproduction signal from a plurality of reproduction signal processors  605  (in this example, reproduction signal processors  605 - 1  and  605 - 2 ) in any arbitrary combination. For example, in the case that reproduction signals P 1  to P 4  from 4 reproduction signal processors  605  are combined arbitrarily to synthesize synthesis signals M 1  to M 4 , synthesis signals M 1  to M 4  are calculated according to the following equation (16).
 synthesis signal  M   1   =K   1   P   1   +K   2 P 2   +K   3   P   3   +K   4   P   4    synthesis signal  M   2   =K   5   P   1   +K   6   P   2   +K   7   P   3   +K   8   P   4    synthesis signal  M   3   =K   9   P   1   +K   10   P   2   +K   11   P   3   +K   12   P   4    synthesis signal  M   4   =K   13   P   1   +K   14   P   2   +K   15   P   3   +K   16   P   4    
   Coefficients K 1  to K 16  are 0 or 1. 
   According to the structure shown in  FIG. 72 , the synthesis signal which is formed by connecting a plurality of reproduction signals as shown in  FIG. 73  intermittently can be generated. In detail, the block B 2  of the reproduction signal  1  and the block B 4  of the reproduction signal  2  are combined, and the combined synthesis signal (block B 5 ) can be recorded. When this recorded signal is reproduced, the signal is reproduced in the order of block B 1 , block B 5 , and block B 3 . 
   As described herein above, the reproduction signal processing block and the recording signal processing block are highly independent, and can be combined arbitrarily, therefore for example, when a signal processing block is in failure, the process which is performed by this signal processing block can be performed by another signal processing block. Further, for example, when it is required to synthesize many reproduction signals in a short time, a prescribed number of reproduction signals out of many reproduction signals is synthesized and recorded temporarily, and residual reproduction signals are combined to the recorded signal, and the number of reproduction signal processing blocks which are operated simultaneously can be reduced thereby. 
   Further, for example, 24 channel reproduction signal processing blocks and recording signal processing blocks are used as 6 independent apparatuses, each apparatus comprises 4 channel reproduction signal processing blocks and recording signal processing blocks. Alternatively, arbitrary number of reproduction signal processing blocks and recording signal processing blocks out of 24 channel reproduction signal processing blocks and recording signal processing blocks are allocated for use as the audio signal corresponding to 6 channel video signal. 
   Next, the reference signal generated from the reference signal generator  601  is described. As described herein above, in the case of this embodiment, the reference signal is generated at the timing when the sync signal of 1 frame video signal is reproduced (video frame frequency). Therefore, in the case that the audio signal corresponding to the video signal is reproduced at a normal rate, the period of reproduction of 1 frame is regarded as fixed period, the generation timing of the reference signal can be calculated, and it is not necessarily required that the reference signal is generated every frame. 
   However, the NTSC video frame frequency is 30000/1001 Hz, the ratio to 48 kHz, that is the audio sampling frequency, is 30000/1001:48000=1:1601.6, namely ininteger form, 5 frame 8008 words. As it is obvious from this ratio, the sampling period of the audio signal coincides with the video frame period only once per 5 frame video signal. As the result, when the audio signal is reproduced corresponding to the video signal from an arbitrary video frame, the deviation between the video signal and audio signal is accumulated gradually with time. To avoid this problem, it has been general to divides 8008 words, which is the number of samplings corresponding to 5 frames of the video signal, into, for example, 1602+1601+1602+1601+1602 (words) so that the sampling period of the audio signal is coincident with an arbitrary frame. Because the number of words is 1601 words or 1602 word and is not the same regarding the audio signal corresponding to each frame, it is not possible to calculate correct generation timing of REC_REF around the reference signal using generation timing of one reference signal. 
   To calculate correctly the REC_REF around the reference signal from the reference signal in an arbitrary frame, as shown in  FIG. 74 , the phase 0 to phase 4 are set to the audio signal corresponding to the frame 0 to the frame 4 of the video signal, and the information is recorded. The phase 0, phase 2, and phase 4 consist of 1602 words respectively, and the phase 1 and phase 3 consists of 1601 words respectively. 
   For example, when the phase 1 and the following phases of the audio reproduction signal reproduced from the reproduction ring buffer  603  are recorded on the recording buffer  611 , the information for indicating that the head of the recording block (recording BLOCK 1) is the phase 1 is recorded simultaneously together with the audio signal. This recording block is recorded on the hard disk  201  through the bus controller  612 , and the DMA bus  251 . In this case, when this block (recording BLOCK 1) is reproduced, the frame position is determined by referring the head phase information, for example, when the recording block is reproduced from the frame position of the third from the head of the corresponding video signal, the third frame position is determined correctly by calculating 1601+1602+1601 (words) because the head is the phase 1. 
   This phase information is the same for all the recording ring buffers  611  always regardless of the existence of record. 
   As described herein above, the variable speed reproduction processor  510  is capable of variable speed reproduction without changing musical interval of the input audio signal. To perform such processing, the source sound data string X(n), which is divided to segments (in this example, segment [0] to segment [E]) having a prescribed number of sampling N (N is a number of 2 to the power) as shown in  FIG. 75A , and then, the data of the basic pitch period (described hereinafter) extending over two segments is thinned from the adjacent two segments as shown in  FIG. 75B  for compression-reproduction, and on the other hand, the data of the basic pitch period is interpolated between the adjacent segments as shown in  FIG. 75C  for expansion-reproduction. 
     FIG. 76  shows the detailed structure of the variable speed reproduction processor  510  for performing such processing. A memory  701  stores the input audio signal, and delivers the audio signal stored based on control of a memory control section  703  to a pitch extraction section  702  and an audio concatenation processor  704 . The pitch extraction section  702  extracts the basic pitch period of the input audio signal, and supplies it to the audio concatenation processor  704  and the memory control section  703 . 
   Generally, the autocorrelation function is used to determine the basic pitch period P of discrete-time sequence (source sound data sequence) X(n). The auto correlation function φ(m) of the discrete-time sequence (source sound data sequence) X(n) is calculated from the following equation (17).
 
φ( m )=(Σ X ( n )· X ( n+m ))/ N m= 0, 1, 2 . . . ,  N− 1  (17)
 
   Herein, m is correlation lug, and Σ is the sum of n from 0 to N−1. 
   Assuming that N is a number of 2 to the power in the equation (17), then calculation of 1/N can be performed by the shift circuit, and the autocorrelation function φ(m) is calculated from the result of the following equation (18).
 
φ′( m )=(Σ X ( n )· X ( n+m ))  m= 0, 1, 2, . . . ,  N −1  (18)
 
   Herein, m is correlation lug, and Σ is the sum of n from 0 to N−1. 
     FIG. 77  shows the detailed structure of the pitch extraction section  702  for performing calculation of the equation (18). After all the source sound data sequence X(0) to X(2N) as shown in  FIG. 78  is entered in memories  711  and  712 , a memory controller  716  controls the memories  711  and  712  to deliver the source sound data sequence X(n) or X(n+m) simultaneously one by one to a multiplier  713 . The multiplier  713  multiplies the input source sound data sequence X(n) and X(n+m) and delivers it to an accumulator  714 . The accumulator  714  calculates the accumulated sum of X(n)·X(n+m) wherein n is from 0 to N−1 entered sequentially from the multiplier  713 . A memory  715  is controlled by the memory controller  716  so as to store φ′(m) namely the calculation result of the accumulator  714 . A timing controller  717  controls the operation timing of the multiplier  713 , accumulator  714 , and memory controller  716 . 
   The value of m that maximizes any one of φ′(m) (m=1, 2, . . . , N−1) stored in the memory  715  is extracted as the basic pitch period P. 
   Further in this embodiment, the autocorrelation function is calculated after all the source sound data sequence X(0) to X(2N) is entered to the memories  711  and  712 , however, because φ′(m) of the equation (18) can be calculated as long as the source sound data sequence X(0) to X(N−1+m) is available, a method in which calculation of φ′(m) starts at the time point when the source sound data sequence X(0) to X(N−1+m) is written in the memories  711  and  712 , and after calculation is completed, the source sound data sequence X(N−1 30  m+1) is written in the memories  711  and  712  and supplied to the subsequent stage for calculation of φ′(m+1). 
     FIGS. 79A to 79F  show the time axis compression reproduction processing performed by the audio concatenation processing  704 . This processing is performed by thinning X(0) to X(p) namely source sound data of the basic pitch period from the continuous (adjacent) segment [K] and segment [K−1] containing N source sound data string as shown in  FIG. 79A . 
   In detail, the audio concatenation processor  704  generates a data string as shown in  FIG. 79B  that the part of the pitch period P of the segment [K] is removed (thinned) from the signal shown in  FIG. 79A . The reproduction time of the source sound data string X(P+1) to X(2N−1) is shifted to the left side on the time axis by the basic pitch period P (shifted forward). However, if the data string is reproduced as it is, noise will be generated at the portion where the temporally discontinuous part is reproduced continuously. To prevent generation of the noise, fade processing is performed. 
   In detail, the data string shown in  FIG. 79B  is supplied to the cross fade DSP  513  as the fade-in data string Xin (n). The fade-in gain coefficient string Kin (n) is multiplied to the fade-in data string Xin (n). This value increases linearly to 0 to 1. On the other hand, the source sound data string X(0) to X(p) (the data string of the pitch period P shown in  FIG. 79A ) to be thinned shown in  FIG. 79D  is the fade-out data string Xout (n).  FIG. 79E  shows the fade-out gain coefficient string K out (n) to be multiplied to the fade-out data string Xout (n), and the value decreases to 1 to 0. 
   The built-in circuit in the audio concatenation processor  704  shown in  FIG. 80  performs calculation of the following equation (19) using the data string described herein above, and delivers an output data string Yn shown in  FIG. 79F .
 
 Y ( n )= Kin ( n )· Xin ( n )+ Kout ( n )· Xout ( n )  (19)
 
   Multiplication of the first term of the right side member in the equation shown above is performed by a multiplier  731 , multiplication of the second term is performed by a multiplier  733 , and addition of both products is performed by an adder  732 . 
   The above-mentioned processing is performed on a prescribed pair out of the segment [0] to the segment [E], then reproduction time is shortened without change of musical interval and an output data string Ym (n) with suppressed ion generation is obtained. 
     FIGS. 81A to 81F  show the time axis expansion reproduction processing by the audio concatenation processor  704 . This processing is performed by adding the source sound data of the basic pitch period to continuous (adjacent) segment [K] and segment [K+1] containing N source sound data strings as shown in  FIG. 81A . 
   In detail, the audio concatenation processor  704  generates a data string (the data string to which the data of the basic pitch period P is interpolated), which data string is formed by shifting the source sound data string X(N−P) to X(2N−1) to the right by the basic pitch period P on the time axis as shown in  FIG. 81B , correspondingly to the pitch period P from the pitch extraction section  702 . This data string is the fade-in data string Xin (n).  FIG. 81C  shows the fade-in gain coefficient string Kin (n) to be multiplied to the fade-in data string Xin (n), the value increases linearly to 0 to 1.  FIG. 81D  shows the source sound data string X(0) to X(2N−1) and this data string is the fade-out data string Xout (n). This data string is the same data string as the data string shown in  FIG. 81A .  FIG. 81E  shows the fade-out gain coefficient string Kout (n) to be multiplied to the fadeout data string Xout (n), and the value decreases to 1 to 0. 
   The built-in circuit in the audio concatenation processor  704  performs calculation shown by the equation (19) using the data described herein above, and an output data string Y (n) shown in  FIG. 81F  is delivered. 
   The above-mentioned processing is performed on a prescribed pair out of the segment [0] to segment [E] shown in  FIGS. 75A to 75C , and an output data string Yp (n) with expanded reproduction is thereby obtained without changing of musical interval. 
   The number of channels of blocks, buses, and SDI in the above-mentioned embodiments are only examples, and can be changed as required. Further the number of subblocks which are formed by dividing 1 frame data and the number of words of a packet transfer block which are formed by dividing further each subblock can be also changed as required. The RAID can be set to an arbitrary number. 
   Computer programs used for performing the abovementioned processes may be supplied to users in the form of distribution media comprising information recording media such as magnetic disks and CD-ROM, and also through the network distribution media such as the internet and digital satellite.