Method and apparatus for transmitting and/or receiving a digital signal

Abstract: A rotary head type digital tape recorder in which a PCM signal and sub data for control and the like concerned with the PCM signal are recorded and/or reproduced by rotary heads. The invention relates to a method and apparatus for transmitting and/or receiving a digital signal in such a type of digital tape recorder by using a data format such that when the serial data is input and output each of a predetermined number of words of the reproduced PCM signal and each symbol of the reproduced sub data are transmitted as a pair synchronously with the rotation of the rotary heads. Thus, a large amount of sub data can be input and output together with the PCM signal.

Description: The present invention relates to a digital tape recorder and, more particularly, to a method and apparatus for reproducing and/or recording a digital signal in a rotary head type digital tape recorder. There exists a so called R-DAT standard, concerning a rotary head type digital tape recorder for recording/reproducing a digital audio signal (PCM signal) by a pair of rotary heads. The R-DAT standard is described e.g. in "80th AES Convention 1986, March 4-7. Preprint 2318(A7)", in EP-A-149 245 or in JP-A-60-140 570. It will be comprehensively explained in the following. In a digital tape recorder using said standard sub codes such as the program number, the time code, and the like are recorded. In addition, PCM-IDs for identifying the sampling frequency, the number of channels, and the number of digitization bits of the PCM signal, the presence or absence of preemphasis, the characteristic thereof, and the like are recorded together with the PCM signal. In the digital tape recorder according to said standard, the PCM signal can be input and output in the form of serial data in order to be able to supply an analog audio signal as the recording input signal, to obtain an analog audio signal as the reproduction output signal, and to make it possible to easily digitally couple with other PCM apparatuses such as other digital tape recorders, digital mixers, and the like. In this case, it is necessary to transmit the sub data together with the PCM signal. Several formats have been proposed by EBU, Philips, and others as standards for the PCM signal transmitting systems. According to the format of EBU, the auxiliary bits of four bits and the user data of one bit for the sub code of the compact disc are assigned to one audio sample data. According to the format of Philips, the PCM signal and the other data are multiplexed when transmitted and received. In the case of the proposed rotary head type digital tape recorder, there is a large amount of sub -i data of the sub codes and PCM-ID. Therefore, the sub data cannot be transmitted by any of these conventional PCM signal transmitting systems. From JP-A-59-16111 it is known that a digital tape recorder may use a bus for transmitting data and may use RAMs for buffering data when logically treating the data. The document EP-A-37 487 discloses that, instead of placing sub data only at the beginning and the end of a recording area, it is preferable to interleave the sub data over the whole area to reduce the influence of a signal dropout. It is an object of the present invention to provide a method and apparatus for transmitting and/or receiving a digital signal in a rotary head type digital tape recorder in which a large amount of sub data can be input and output together with the PCM signal as compared with a compact disc or the like. A method of recording according to the invention is set out in claim 1. A method of reproducing according to the invention is set out in claim 4. Claims 5 and 6 contain corresponding apparatus according to the invention. The above and other objects and features of the present invention will become apparent from the following detailed description and the appended claims with reference to the accompanying drawings. Fig. 1 is a block diagram showing an overall constitution of a rotary head type digital tape recorder to which the present invention can be applied; Fig. 2 is a schematic diagram showing a tape format of the digital tape recorder; Figs. 3A to 3E are schematic diagrams for explaining a track format and a block format of the digital tape recorder; Figs. 4A and 4B are schematic diagrams for explaining error correction codes of the digital tape recorder; Fig. 5 is a block diagram of the main section of an embodiment of the invention; Figs. 6 and 7 are time charts for explaining the reproducing and recording modes of transmission data; Figs. 8 to 10 are schematic diagrams for explaining the sub data; and Fig. 11 is a time chart for explaining the transmission data. An embodiment when the present invention is applied to a rotary head type digital tape recorder (hereinafter, abbreviated to an RDAT) will be described in detail hereinbelow with reference to the drawings in accordance with the following order. a. Overall constitution of a digital tape recorder; b. Data constitution of a digital tape recorder; c. Error correction codes of a digital tape recorder; d. Recording signal processor and reproduction signal processor according to the present invention; and e. Data recording/reproducing system according to an embodiment of the present invention. a. Overall constitution of a digital tape recorder: Fig. 1 shows an overall constitution of a rotary head type digital tape recorder (i.e., RDAT) for use with the present invention. In the diagram, reference numeral 1 denotes a drum having a diameter of 30mm which is rotated at a speed of 2000 r.p.m. A pair of magnetic heads 2A and 2B are attached to the drum 1 with an angular interval of 180°. A magnetic tape 3 (indicated by an alternate long and short dash line) is obliquely wound around the peripheral surface of the drum 1 at a wrap angle of 90°. The magnetic tape 3 is laid between reel hubs 4A and 4B of a tape cassette and is moved at a speed of 8.15 mm/sec by a capstan 5 and a pinch roller 6. As the drum 1 is rotated, the magnetic heads 2A and 2B alternately come into contact with the magnetic tape 3, thereby writing or reading oblique tracks 7A and 7B onto the magnetic tape 3 as shown in Fig. 2. A tape width A of the magnetic tape 3 is 3.81 mm. The magnetic gap of the rotary head 2A is inclined by an angle of inclination of +α with respect to the direction perpendicular to the track. The magnetic gap of the other rotary head 2B is inclined by an angle of inclination of -α with regard to the direction perpendicular to the track. The value of α is set to 20°. The angles of the magnetic gaps of the magnetic heads 2A and 2B are called + azimuth and - azimuth, respectively. The magnetic heads 2A and 2B are alternately selected by a head change-over switch 8. The recording signal from a terminal r of a recording/reproducing switch 9 is supplied to the magnetic heads 2A and 2B through rotary transformers (not shown). The read signals of the magnetic heads 2A and 2B are taken out to a terminal p of the switch 9 through the rotary transformers (not shown). The analog audio signal from an input terminal 10 is supplied to an A/D converter 12 through a low pass filter 11 and converted into a digital audio signal (at a sampling frequency of 48 kHz on the basis of a linear digitization of 16 bits). The digital audio signal from the A/D converter 12 is supplied to a recording signal processor 13. In the processor 13, the digital audio signal is subjected to an error correction coding process and converted into the format of the recording data, which will be explained hereinafter. In this case, an ID signal (PCM-ID) to identify the on/off of the preemphasis of the signal to be recorded, the sampling frequency, the number of digitization bits, and the like is added. The sub codes such as the program number, the time code, and the like of the signal to be recorded, and an ID signal (sub code ID) for the sub codes are formed by a sub code encoder (not shown) and supplied from a terminal 14 to the recording signal processor 13. Serial recording data for each track is generated from the processor 13 synchronously with the rotation of the magnetic heads 2A and 2B. The recording data is supplied to the head change-over switch 8 through a recording amplifier 15 and the terminal r of the recording/reproducing switch 9. The recording data is alternately supplied to the magnetic heads 2A and 2B by the switch 8. During reproduction, the signals read by the magnetic heads 2A and 2B are supplied to a reproducing amplifier 16 through the switch 8 and through a terminal p of the switch 9. The output signal of the reproducing amplifier 16 is supplied to a phase locked loop (PLL) 17. In the PLL 17, the clock signal synchronized with the reproduced signal is extracted. In a reproduction signal processor 18, the reproduced signal from the PLL 17 is subjected to the processes of error correction, interpolation, and the like. The reproduced digital audio signal is supplied to a D/A converter 19. The reproduced audio signal from the D/A converter 19 is taken out to an output terminal 21 through a low pass filter 20. Further, the sub codes and sub code ID are separated by the reproduction signal processor 18 and taken out to an output terminal 22. A sub code decoder (not shown) is connected to the output terminal 22 and control data and the like are formed from the sub codes. Control signals to control the head change-over switch 8 and recording/reproducing change-over switch 9 are formed by a timing controller 23 from a PG pulse indicative of the rotation of the heads. In addition, the timing controller 23 generates clock signals and timing signals which are respectively necessary for the recording signal processor 13 and reproduction signal processor 18 using the clock signal, block sync signal, and the like from the PLL 17. b. Data constitution of a digital tape recorder: The whole part of the data to be written in a single track is called one segment. Fig. 3A shows a constitution of the data of one segment which is written by one rotary magnetic head. Assuming that a unit amount of the recording data is one block, the data of 196 blocks (7500 µsec) is included in one segment. Margins (eleven blocks) are provided in both end portions of one segment corresponding to the edge portions of the track, respectively. A sub code 1 and a sub code 2 are recorded in the portions adjacent to those margins, respectively. These two sub codes are the same data and this data is recorded twice. The sub code includes the program number and time code. A run-in interval (two blocks) of the PLL and a postamble interval (one block) are arranged on both sides of the recording area of eight blocks of each sub code. Several inter block gaps (GAP) in which no data is recorded for three blocks are also provided. A pilot signal for the ATF is recorded in five blocks between the 3-block inter block gaps. The PCM signal which was subjected to the recording process is recorded in an area having a length of 128 blocks, i.e., excluding the run-in interval of the PLL of two blocks within an area having a length of 130 blocks of the central portion of one segment and between inter block gaps (GAP). This recorded PCM signal is the data corresponding to the audio signal for the period of time when the rotary head rotates by only the amount corresponding to a half rotation of the drum 1. The recorded PCM signal consists of the two-channel stereophonic PCM signals of right (R) and left (L) channels and the parity data of the error detection/correction codes. When one segment as shown in Fig. 3A is written by the magnetic head 2A, the data Le is recorded in the left half portion of the PCM signal recording area and the data Ro is recorded in the right half portion. The data Le consists of the even-number designated data of the L channel and the parity data regarding this data. The data Ro consists of the odd-number designated data of the R channel and the parity data concerned with this data. The odd number and even number are the order numbers when they are counted from the beginning of the interleave block. The data of one segment is recorded in another track which is written by the other rotary magnetic head so as to have the same constitution as that of the above described track except that the data Re is recorded in the left half portion of the data interval in the data of one segment in the other track, and the data Lo is recorded in the right half portion. The data Re consists of the even-number designated data of the R channel and the parity data regarding this data. The data Lo consists of the odd-number designated data of the L channel and the parity data with respect to this data. In this manner, the even-number designated data and odd-number designated data of each channel are recorded in two adjacent tracks and, at the same time, the data of the L and R channels are recorded in the same track. The reason why the data is recorded in this way is to prevent the possibility that continuous data of the same channel might become error data due to dropout of the signal and the like. Fig. 3B shows a data constitution of one block of the PCM signal. A block sync signal of eight bits (one symbol) is added to the head of one block. Then, a PCM-ID of eight bits is added. After the PCM-ID, a block address is added. A simple parity error correction coding process is performed with respect to two symbols (W₁ and W₂) of the PCM-ID and block address. An eight-bit parity is added after the block address. As shown in Fig. 3D, the block address is constituted by seven bits excluding the most significant bit (MSB). When the MSB is set to "0", this means that this block is the PCM block. The block address of seven bits sequentially changes such as (00) to (7F) (hexadecimal notation). The PCM-ID which is recorded into each block having the block address whose lower three bits are (000), (010), (100), or (110) is preliminarily determined. The optional code of the PCM-ID can be recorded as each block address whose lower three bits are (001), (011), (101), or (111). ID₁ to ID₈ each consisting of two bits and the frame address of four bits are included in the PCM-ID. The identification information is defined for each of the ID₁ to ID₇. One pack is constituted by thirty-two ID₈. For example, the ID₁ is the format ID and the kind of application for audio use or other use is identified by the ID₁. The on/off of the preemphasis and the characteristic of the preemphasis are identified by the ID₂. The sampling frequency is identified by the ID₃. The foregoing 1D₁ to ID₇ and the frame address have the same data in the segments of the interleave pair. Fig. 3C shows a data constitution of one block of the sub codes. The data constitution is similar to that of the foregoing PCM block. As shown in Fig. 3E, the most significant bit of the symbol W₂ of the sub code block is set to "1", thereby indicating that the block is the sub code block. The lower four bits of the symbol W₂ are used as the block address. Eight bits of the symbol W₁ and three bits in the symbol W₂ excluding the MSB and the block address in the symbol W₂ are used as the sub code ID. A simple parity error correction coding process is executed with regard to two symbols (W₁ and W₂) of the sub code block and a parity of eight bits is added. The data of the sub code ID which is recorded in the even number designated block addresses (the LSB (least significant bit) of the block address is "0") differs from the data of the sub code ID which is recorded in the odd number designated block addresses (the LSB of the block address is "1"). The sub code ID includes the control ID, time code, and the like to designate the reproducing method. The sub code data is subjected to the error correction coding process by the Reed Solomon code similarly to the PCM data. c. Error correction codes of a digital tape recorder: The processes of the error detection/correction codes are executed for the data of each one of the 128 blocks to be recorded in one segment. Fig. 4A shows a code constitution of the data to be recorded by the magnetic head 2A. Fig. 4B shows a code constitution of the data to be recorded by the other magnetic head 2B. The PCM signal in which the number of digitization bits is sixteen is divided into an upper eight bits and a lower eight bits, and the coding processes of the error detection/correction codes are performed in a manner such that eight bits are used as one symbol. The data of 4096 (= 128 x 32) symbols is recorded in one segment. As shown in Fig. 4A, the C₁ and C₂ error correction coding processes are executed with respect to each of the vertical and horizontal directions of the two-dimensional arrangement of the data consisting of the even-number designated data Le of the L channel comprising the symbols of (L₀, L₂, ..., L₁₄₃₈) and the odd-number designated data Ro of the R channel comprising the symbols of (R₁, R₃, ..., R₁₄₃₉). A C₁ coding process using a Reed Solomon code of (32, 28, 5) is performed with regard to the twenty-eight symbols in the vertical direction. The parity data P of four symbols of the C₁ code is arranged at the last position of the two-dimensional arrangement. A C₂ coding process using a Reed Solomon code of (32, 26, 7) is performed with regard to the fifty-two symbols in the horizontal direction. The coding process of the C₂ code is executed with respect to the twenty-six symbol pairs of every two symbols among the fifty-two symbols. The parity data Q consisting of six symbols is generated with respect to one code series. The parity data Q consisting of a total of twelve symbols of the C₂ code is arranged in the central portion of the two-dimensional arrangement. The parity data Q consisting of six symbols is generated with respect to one code series. The parity data Q consisting of a total of twelve symbols of the C₂ code is arranged in the central portion of the two-dimensional arrangement. Similarly, the C₂ coding process is also executed with regard to the symbols of the other 52 PCM data in the horizontal direction and the parity data Q is arranged in the central portion. The code constitution shown in Fig. 4B is obtained by replacing the even-number designated PCM signals of the L channel in the code constitution shown in Fig. 4A by the even-number designated PCM signals (R₀, R₂, ..., R₁₄₃₈) of the R channel and by replacing the odd-number designated PCM signals of the R channel by the odd-number designated PCM signals (L₁, L₃, ..., L₁₄₃₉) of the L channel. As shown in Fig. 3B, one PCM block is constituted by adding the sync signal, PCM-ID, block address, and parity to the 32 symbols arranged in the vertical direction in those code constitutions. d. Recording signal processor and reproduction signal processor in an apparatus according to an embodiment of the present invention: Digital input data can be supplied to the recording signal processor 13 in the foregoing digital tape recorder separately from the analog audio signal supplied to the input terminal 10. Also digital output data can be derived from the reproduction signal processor 18 separately from the reproduced audio signal taken out to the output terminal 21. The reason for separately deriving the digital output data is to digitally connect the digital tape recorder with another PCM apparatus in order to perform digital dubbing or the like. The present invention is applied to the generation of the foregoing serial data. Fig. 5 shows a constitution of the recording signal processor and reproduction signal processor of the apparatus of the present invention. In Fig. 5, the PCM signal from the A/D converter 12 or serial data from another digital tape recorder, digital mixer, or the like is supplied to an input terminal 31. The input digital signal is supplied to series/parallel converters 33 and 34 which are constituted by shift registers. The PCM signal is separated by the series/parallel converter 33 and the sub codes are separated by the other series/parallel converter 34. The PCM signal in which one sample consists of sixteen bits is divided into the upper eight bits and the lower eight bits. The error correction coding process and digital modulating process are executed for each eight bit symbol. One symbol of the sub codes consists of eight bits. The eight-bit parallel data is supplied from each of the series/parallel converters 33 and 34 to a data bus 37 through a multiplexer 35 and a buffer 36. The buffer 36 is controlled by a control signal from a request controller 38 and is set into the active state at a predetermined timing. A request signal is supplied from a crystal controlled timing generator 39 to the request controller 38. The timing generator 39 generates not only the request signal but also clock signals comprised of a bit clock BCK, a word clock WCK, and a clock LRCK for identifying the L (left) or R (right) channel, and a control signal. The input data transmitted from the data bus 37 is written into a buffer RAM 40. An address to write the input data into the buffer RAM 40 is formed by an address generator 41. The address generator 41 produces a write address using the clocks from the timing generator 39. The data stored in the buffer RAM 40 is supplied to a parity generator 42 through the data bus 37 in accordance with a predetermined order. In the parity generator 42, a parity P of the error correction code C₁ and a parity Q of the error correction code C₂ are generated with respect to the PCM signal to be recorded in one segment. The sub codes are also subjected to the error correction coding process in the parity generator 42. The produced parity symbols are written into the buffer RAM 40 through the data bus 37. The addresses necessary to produce the parity symbols are generated from the address generator 41. The parity generator 42 supplies timing signals indicative of the starts of the C₁ and C₂ coding processes to the address generator 41. A sub code I/O circuit 43 is connected to the data bus 37. The sub codes from the input terminal 14 are written into the buffer RAM 40 through the sub code I/O circuit 43 and data bus 37. The error correction coded PCM signal and the sub codes are supplied to a register 45 through a buffer 44. The output signal of the register 45 is supplied to a modulator 46. The modulator 46 converts eight bit symbols into ten bit patterns. The low frequency components in the recording data which is taken out from the modulator 46 to an output terminal 47 are reduced by the digital modulation, so that no waveform distortion is caused and the digital signal from which the clocks can be easily extracted on the reproduction side is obtained. The reproduced signal from an input terminal 51 is supplied to a demodulator 52 and one symbol and ten bits are demodulated into one symbol and eight bits. The reproduced data from the demodulator 52 is supplied symbol by symbol to the data bus 37 through a register 53 and a buffer 54. The buffer RAM 40 and an error correcting circuit 56 are connected to the data bus 37. The reproduced data is stored into the buffer RAM 40 from the data bus 37. In the error correcting circuit 56, the data stored in the buffer RAM 40 is subjected to the error correcting processes (C₁ decoding and C₂ decoding) by use of Reed Solomon codes. The error corrected PCM signal and the sub codes are read out of the buffer RAM 40 and supplied to a register 57 through the data bus 37. The register 57 is controlled by the control signal from the request controller 38. A block address detecting circuit 55 is provided in conjunction with the demodulator 52. The reproduction block address is detected by the block address detecting circuit 55. The reproduction block address is supplied to the address generator 41. The reproduction address generated from the address generator 41 is set to the address signal of the buffer RAM 40. The reproduction block address is used to write the reproduced data of one segment (32 symbols x 128 blocks) (refer to Fig. 4) for each block in the order from the first block to the 128th block. The address for the ECC (error correcting circuit) is also produced by the address generator 41. The ECC address is supplied to the buffer RAM 40. The ECC address is used to read out the data from the buffer RAM 40 for the respective C₁ and C₂ decoding processes and to write the error corrected data and pointers into the buffer RAM 40. The timing signals indicative of the start timings of the respective C₁ and C₂ decoding processes are supplied from the error correcting circuit 56 to the address generator 41. The PCM signals which were subjected to the C₁ and C₂ decoding processes and the error corrected sub codes are read out of the buffer RAM 40. In this case, the stereophonic signals of two channels are formed by the PCM signals which had been reproduced from two tracks of the interleave pair and which were error corrected. In order to read out the error corrected PCM signal from the buffer RAM 40, the addresses formed by the address generator 41 are supplied to the buffer RAM 40. The PCM signal and sub codes which were read out of the buffer RAM 40 are supplied to the register 57. The reproduced sub codes are supplied to a system controller (not shown) through the sub code I/O circuit 43. Parallel/series converters 58 and 59 are connected to the register 57. The PCM signal is supplied to the parallel/series converter 58 and the sub codes are supplied to the parallel/series converter 59. The serial data PCM signal, as converted by the parallel/series converter 58, is supplied to an interpolating circuit 60 where the uncorrectable errors are interpolated. The output signal of the interpolating circuit 60 is supplied to a multiplexer 62. The operation of the interpolating circuit 60 is controlled by a control signal from an interpolation control circuit 61. In the interpolating circuit 60, the words of the PCM signal whose errors could not be corrected are interpolated by a previous value holding process, an average value interpolating process, or the like. The PCM signal from the interpolating circuit 60 is supplied to the multiplexer 62. The sub codes from the parallel/series converter 59 are delayed by a shift register 63 and supplied to the multiplexer 62. The shift register 63 is provided to delay the input signal from the converter 59. The output signal of the multiplexer 62 is taken out to a digital output terminal 65 through a shift register 64. The PCM signal or the serial data in which the PCM signal and the sub data are mixed as will be explained hereinafter is supplied to a digital output terminal 65. e. Data reproduction apparatus according to the present invention: The serial data which is input from the digital input terminal 31 or output from the digital output terminal 65 in the foregoing recording signal processor and reproduction signal processor will now be described. Fig. 6A shows the reproduced RF signal which was alternately read by the magnetic heads 2A and 2B. The reproduced RF signal is reproduced within a range of the rotational angle of 90°. In Fig. 6A, (+) and (-) denote the azimuths (+ azimuth and - azimuth) of the gaps of the respective magnetic heads 2A and 2B. SA, SB, and SC indicate the sub data (sub codes, sub code ID, and PCM-ID) included in the reproduced RF signal of each segment. An output sync signal EXSY, synchronized with the rotation of the magnetic heads 2A and 2B and shown in Fig. 6B, is formed by rotation detectors provided in conjunction with the magnetic heads. The PCM signal and sub data SA and SB which were read by the magnetic heads 2A and 2B are output as serial data DADT from the output terminal 65 during the period of time of the next rotation of the heads as shown in Fig. 6C. Since the rotational speeds of the magnetic heads 2A and 2B are 2000 r.p.m., it takes 30 msec for the magnetic heads to rotate once. The serial data DADT includes the PCM signal and sub data of one segment during every time slot of 15 msec. The sub data and PCM signal are time-divisionally or alternatively inserted during a period of time corresponding to 472 word clocks in a time slot of 15 msec as will be explained hereinafter and as shown in Figure 11J. This inserting process is performed by the multiplexer 62. In the recording mode, the serial data ADDT shown in Fig. 7C is supplied to the digital input terminal 31. Similar to the serial data DADT shown in Fig. 6C, the serial data ADDT is the data in which the sub data and PCM signal were time-sharingly multiplexed for the period of time of 472 word clocks in the time slot of 15 msec. The serial data is synchronized with the output sync signal EXSY and separated into the PCM signal and the sub data by the serial/parallel converters 33 and 34. The PCM signal and sub data which were separated from the serial data are subjected to the error correcting process and the like, respectively. Thereafter, they are supplied as the recording signals shown in Fig. 7A to the magnetic heads 2A and 2B. There is a time deviation of one rotation of the magnetic heads 2A and 2B between the recording signal and the input serial data. The sub data included in one segment which is recorded in each track will now be described with reference to Figs. 8 to 10. Fig. 8 shows the sub code data. The sub code data S₁ to S₄₄₈ each consisting of eight bits are arranged in a matrix form. The error correction coding process by use of a Reed Solomon code of (32, 28, 5) is executed for every sub code data of twenty-eight symbols. This error correction code is the same as the error correction code C₁ which is applied to the PCM signal. The parity data C₁-P of eight symbols included in two code series are collectively arranged. The sub code data and parity data C₁-P are inserted into the respective block addresses of (0 to F) (hexadecimal notation). The data included in eight block addresses of (0 to 7) is set to the sub code 1. The data included in eight block addresses of (8 to F) is set to the sub code 2. The sub codes 1 and 2 are recorded into the different recording areas of the same track for every block address. The data shown in Fig. 9 is recorded in the sub code ID in the sub code block. The sub code data S₄₆₅ and S₄₆₆ are recorded as W₁ and W₂ in the sub code blocks whose block addresses are (0 x x 0) (where, x = 0 or 1), namely, (0, 2, 4, 6). The sub code data S₄₆₇ and S₄₆₈ are recorded as W₁ and W₂ in the sub code blocks 7). The sub code data S₄₆₉ and S₄₇₀ are recorded in the sub code blocks whose block addresses are (1 x x 0), i.e., (8, A, C, E). The sub code data S₄₇₁ and S₄₇₂ are recorded in the sub code blocks whose block addresses are (1 x x 1), i.e., (9, B, D, F). The four-bit block addresses are also included in the sub code data S₄₆₆, S₄₆₈, S₄₇₀, and S₄₇₂, respectively. The time code information and control information of the reproducing operation are included in the sub code ID. The PCM-ID shown in Fig. 10 is recorded as the PCM-ID (W₁) in the PCM block. The data S₄₄₉ which is recorded into the PCM block of the block address whose lower three bits are (000) includes ID₁ (two bits) and ID₂ (two bits) of the ID code and the frame address (four bits). The data S₄₅₁ which is recorded into the PCM block of the block address whose lower three bits are (010) includes ID₃ (two bits), ID₄ (two bits), and frame address (four bits). The data S₄₅₃ which is recorded into the PCM block of the block address whose lower three bits are (100) includes ID₅ (two bits), ID₆ (two bits), and frame address (four bits). The data S₄₅₅ which is recorded into the PCM block of the block address whose lower three bits are (110) includes ID₇ (two bits), ID₈ (two bits), and frame address (four bits). The presence or absence and the characteristic of the emphasis, the sampling frequency, the number of digitization bits, the tape speed, and the like with respect to the recorded PCM signal are identified on the basis of eight ID codes of ID₁ to ID₈. The frame addresses regarding the interleave pair are set to the same code. The symbols S₄₅₀, S₄₅₂, S₄₅₄, S₄₅₆, S₄₅₈, S₄₆₀, S₄₆₂, and S₄₆₄ other than the foregoing symbols of the PCM-ID are the optional codes and are not defined by the standards. Further, S₄₅₇, S₄₅₉, S₄₆₁, and S₄₆₃ are the codes which are not defined at all. The sub data (total 472 symbols/one segment) including the foregoing sub code data, sub code ID, and PCM-ID, is inserted for the first period of time of 472 word clocks in 15 msec of the serial data which is input and output. Each of SA, SB, and SC in Figs. 6 and 7 is the sub data. The arrangements of the sub codes in the serial data DADT and ADDT will now be described with reference to Fig. 11. Fig. 11A indicates the output sync signal EXSY whose level is inverted every 30 msec synchronously with the rotation of the rotary heads 2A and 2B. Fig. 11B shows the clock LRCK to identify the L and R channels. Fig. 11C represents the word clock WCK of the PCM signal. Fig. 11D indicates the bit clock BCK of the PCM signal. One word of the PCM signal consists of sixteen bits and one symbol of the sub data consists of eight bits. In the period of time of 472 word clocks from the edge of the output sync signal EXSY, the words (L₀, R₀, L₁, R₁, ..., L₂₃₅, R₂₃₅) of the PCM signal are inserted for the period of time when the word clock WCK is set to "1". On the other hand, the sub data (S₁, S₂, S₃, S₄, ..., S₄₇₁, S₄₇₂) is inserted for the period of time of eight bit clocks in the latter half of the period of time when the word clock WCK is set to "0", respectively. Only the PCM signal is inserted for the period of time after the period of time of 472 word clocks. Figs. 11F to 11J show time charts in which the time base of the period of time of thirty-two bit clocks is enlarged. The PCM signal of the L channel is inserted for the period of time when the clock LRCK shown in Fig. 11F is set to "0". The period of time of thirty-two bit clocks BCK shown in Fig. 11H is included in one period of time of the word clock WCK shown in Fig. 11G. As shown in Fig. 11I, the bit numbers of thirty-two bits are defined by the bit clock BCK. As shown in Fig. 11J, the PCM signal (L₀) of sixteen bits is located from the 17th bit to the 32nd bit. The sub code S₁ is located from the ninth bit to the sixteenth bit. In a rotary head type digital tape recorder, the sampling frequency is not limited to 48 kHz but may be also set to 32 or 44.1 kHz. Therefore, the number of words of the PCM signal included in one segment changes. However, the sub data is inserted into the serial data DADT or ADDT for the first period of time of 472 word clocks of the time slot of every 15 msec similar to the case where the sampling frequency is 48 kHz. The data blank interval of eight bit clocks is included in the period of time of thirty-two bit clocks when the PCM signal of one word and the sub data of one symbol are inserted. An auxiliary bit indicative of the effective or ineffective of the data or the user bit which can be specified by the user may be also inserted for the data blank interval as shown in Figure 11E. According to the present invention, a large amount of sub data in the rotary head type digital tape recorder can be inserted into the serial data which is input and output, and the sub data does not need to be transmitted by another channel.

Claims: A method of recording digital data onto a tape by using a tape recorder having rotary heads, said method comprising the steps of: receiving digital data comprising PCM-data and subdata representing control data, said digital data being formated in words, wherein each word is a digital data sample of an analog signal; coding blocks of the received PCM-signal for error correction, each block comprising a predetermined number of words; coding blocks of the received subdata for error correction, each block comprising a predetermined number of words; arranging said coded data into segments, each segment containing a predetermined number of words of error corrected PCM-data and associated error corrected subdata; and writing tracks of data onto said tape, each track containing one of said segments; characterized in that said error corrected PCM-data (LO-236, RO-236) are arranged in units of words, with a gap corresponding to the record length of one word between subsequent written PCM-data words; said error corrected subdata (S1-472) are arranged in units of symbols into at least a part of said gaps, each symbol having half of the length of a word. The method according to claim 1, characterized in that during a first arrangement interval of a segment, a predetermined number of pairs of data, each comprising a PCM-data word and a subdata symbol is serially arranged, whereas in the remaining interval only PCM-data words are arranged, with said gaps between these words. The method according to one of the claims 1 or 2, characterized in that said predetermined number of words is 472. A method of reproducing by a tape recorder having rotary heads a digital signal recorded in a format as achievable by the method of claim 1, a predetermined number of pairs being formed in each segment of data, each pair comprising a symbol of said subdata and a word of said PCM-data; said method comprising the steps of: reproducing said predetermined number of pairs of data synchronously with the rotation of the rotary head; formating said reproduced data in PCM-blocks and subdata blocks; error correcting said data; and decoding said error corrected PCM-data and subdata and outputting the PCM-signals and subdata signals. An apparatus of recording digital data onto a tape by using a tape recorder having rotary heads, said apparatus comprising: a means (10; 31) for receiving digital data comprising PCM-data and subdata representing control data, said digital data being formated in words, wherein each word is a digital data sample of an analog signal; first means (42) for coding blocks of the received PCM-signal for error correction, each block comprising a predetermined number of words; second means (42) for coding blocks of the received subdata for error correction, each block comprising a predetermined number of words; means (44) for arranging said coded data into segments, each segment containing a predetermined number of words of error corrected PCM-data and associated error corrected subdata; and means (2A, 2B) for writing tracks of data onto said tape (3), each track containing one of said segments; characterized in that said means for arranging said data is designed to arrange said error corrected PCM-data in units of words, with a gap corresponding to the record length of one word between subsequent written PCM-data words; and arrange said error corrected subdata in units of symbols into at least a part of said gaps, each symbol having half of the length of a word. An apparatus for reproducing digital data as recorded on a tape (3) with a format as achievable by the method of claim 1, said apparatus comprising: rotary heads (2A, 2B) for reproducing said pairs of data synchronously with their rotation; a means (40) for formating said reproduced symbols in PCM-blocks and subdata blocks; a means (56) for error correcting said data; and a means (52) for decoding said PCM-data and subdata and for outputting the PCM-signals and subdata signals.

Inventors: FUKAMI TADASHI, ODAKA KENTARO, OZAKI SHINYA, FUKAMI, TADASHI, ODAKA, KENTARO, OZAKI, SHINYA
Applicants: SONY CORP, SONY CORPORATION
Application year: 1987
Main classification: G11B20
IPC codes: G11B27, G11B20