Apparatus for recording signals on disk recording medium

A recording apparatus of this invention detects the state of management information, which pertains to a recording address of an image signal, and which is reproduced from a disk-like recording medium having a first area for the image signal and a second area for the management information. On the basis of the detection result, management data is reproduced from the first area of the disk-like recording medium. On the basis of the management data reproduced from the first area, the management information reproduced from the second area is modified. A modify unit records the modified management information in the second area.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an apparatus for recording signals such as image signals on a disk recording medium and, more particularly, to control of management information of recorded signals.

2. Related Background Art

Conventionally, a video tape recorder which records analog video signals on magnetic tapes is available as an image recording apparatus for recording video signals on a recording medium. However, with rapid progress of digital signal processing technologies, digital recording/playback apparatuses which record analog video signals on a recording medium by converting the signals into digital video signals are becoming popular at present.

Such digital recording/playback apparatuses include a digital VTR, a digital video disk apparatus which records signals on a solid-state disk or magnetooptical disk, and a solid-state memory video apparatus which records signals in a solid-state memory such as a flash memory or an SRAM.

These digital recording/playback apparatuses load a video signal obtained by an image pickup device such as a CCD and convert the signal into a digital signal by A/D conversion. The apparatuses reduce the information amount by compression-encoding this digital video signal. In this manner, these apparatuses can record a large amount of image information in a small recording capacity.

Schemes used as this compression encoding are discrete cosine transform (to be referred to as DCT hereinafter) which is orthogonal transformation having the highest compression efficiency, and a variable-length coding scheme. To perform compression encoding, a single image is first segmented into a plurality of blocks each having x horizontal pixels and y vertical pixels, and DCT transform is performed for each block. A DCT coefficient after the transform is divided by a certain divisor, and the remainder is rounded, thereby performing quantization. By using the characteristic that a quantized image is concentrated in low-frequency components, the number of bits of high-frequency components is reduced. In this way, the information amount is greatly reduced.

The information amount can be further compressed by performing variable-length encoding, e.g., Huffman coding, which assigns to the quantized data a code length corresponding to the occurrence frequency of the data.

Furthermore, greater compression can be attained by combining interframe predictive encoding which calculates the difference between frames, by using the characteristic that a motion image has a strong correlation between frames.

Of this type of recording/playback apparatuses, the capacities of disk media of disk apparatuses are rapidly increasing in recent years. Consequently, apparatuses which record and play not only audio signals but video signals in and from a disk medium for a long time have been proposed. For example, a technique has been proposed which uses a recording format based on high-efficiency encoding such as MPEG using, e.g., DCT and variable-length encoding described above, and which can realize a recording/playback apparatus which records video signals for one hour or more at data rates of about 4 Mbps and 10 Mbps. Furthermore, disk media themselves are being reliably decreased in size and increased in capacity.

In an image recording apparatus which records video signals on a disk medium by reducing the information amount by compressing the signals by combining the aforementioned compression techniques, the information amount varies in accordance with an image because variable-length encoding is used. Therefore, a rate control means for holding the information amount constant is used to uniformize the recording rate of images, thereby recording images in a predetermined recording media capacity within a predetermined time.

This rate control uniformizes the rate by writing compressed data having variations into a certain predetermined buffer and reading out the data at a constant rate. That is, buffer control is performed such that if the data may exceed a predetermined value of the buffer, the quantization level described above is increased to raise the compression ratio; if the buffer does not satisfy the predetermined value, the quantization level is decreased to lower the compression ratio.

In constant bit rate recording (CBR recording), the recording rate is held constant by giving priority to the target time of recording on a recording medium. Hence, if an input image moves fast or has a wide color band, quantization becomes coarse to make the image nonuniform between frames. Therefore, an image recording apparatus which performs variable bit rate recording (VBR recording) by attaching importance to image quality has been proposed. This VBR recording performs encoding giving priority to image quality by holding the quantization level of recording at a substantially constant value, while allowing fluctuations of the recording rate.

A recording/playback apparatus like this uses management information called Table of Contents (to be referred to as a TOC hereinafter) to control video data recording and playback operations. When video data obtained by image pickup is recorded on a recording medium, the TOC information is recorded in an area formed on the inner peripheral side of the disk medium independently of an area for recording video data. In playback operation, the TOC information is read out from the disk medium and held in an internal memory of the apparatus. On the basis of this TOC information, the position of access to the disk medium and diverse operations such as video data playback management are controlled.

Examples of operations managed using the TOC are an operation of linking data of one scene, which are discontinuously recorded on a recording medium, and continuously displaying back the data, an operation of deleting a scene once obtained by image pickup, and an operation of recording a scene newly obtained by image pickup in a free space formed by deletion.

In any of these operations, video data is recorded in an area (video recording area) formed near the center in the radial direction of a disk medium, and the TOC information is saved in an area (system information management area) formed inside the image recording area. Note that no data can be recorded in the outer periphery of the disk.

Since the TOC is important information necessary to recording/playback, the reliability is improved by, e.g., recording the TOC a plurality of times in the system management area of a disk.

In conventional image pickup recording/playback apparatuses, the TOC is recorded on a disk after video data is completely written in the medium. That is, after the recording end pointer (address) of video data on a disk is determined, various pieces of information including an end pointer and start pointer are recorded as the TOC information.

If, therefore, one recorded scene extends over a long time period, no TOC information may be recorded for long periods of time.

Also, a system using a disk medium can rapidly access data in the disk medium, so recording or playback access to the disk medium is usually intermittently performed. Between this disk access operation and other operations, large differences are produced in consumption power such as motor driving power, head driving power, and write laser power.

When a series of recording operations are performed with battery driving, therefore, the battery supply voltage lowers with an abrupt rise of the consumption power upon disk access. This sometimes makes the recording operations of the system impossible to perform.

Especially when the TOC information is to be recorded, the write operation is performed by moving a recording/playback head mechanism from the video recording area for recording video data to the system management area in a remote position. Hence, if the battery amount remains to such an extent that a video data recording operation is marginally possible, the TOC information cannot be written in the worst case.

If the TOC information is missing, the start pointer, end pointer, attribution, and the like of recorded video data are unknown, so disk medium playback control cannot be performed.

Also, even if the reliability of the TOC data is improved as described previously, recording is sometimes abnormally terminated in the middle of a scene by, e.g., careless handling by a user, running out or abrupt discharge of a battery, a defect of a recording medium, or some external cause. In a case like this, actually recorded images and sounds and additional data sometimes disagree with the contents of the TOC. This makes playback of the scene based on the TOC impossible.

SUMMARY OF THE INVENTION

It is an object of the present invention to solve the above conventional problems.

It is another object of the present invention to reliably record management information such as TOC information on a recording medium without losing the management information, even when the remaining battery amount becomes insufficient during image pickup recording.

It is still another object of the present invention to normally reproduce a recorded signal halfway even when recording of the signal is not normally completed.

To achieve the above objects, according to one aspect of the present invention, there is provided a recording apparatus comprising reproducing means for reproducing management information pertaining to a recording address of an image signal from a disk-like recording medium having a first area for the image signal and a second area for the management information, control means for detecting the state of the reproduced management information by using the management information and, on the basis of the detection result, controlling the reproducing means to reproduce management data from the first area of the disk-like recording medium, modifying means for modifying the management information reproduced from the second area, on the basis of the management data reproduced from the first area, and recording means for recording an image signal in the first area of the disk-like recording medium and recording the management information modified by the modifying means in the second area.

Other objects and features of the present invention will become apparent from the following detailed description of embodiments of the invention taken in conjunction with the accompanying drawings.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1is a block diagram showing the configuration of a recording/playback apparatus100according to the first embodiment of the present invention. Referring toFIG. 1, this recording/playback apparatus100comprises an optical system101including, e.g., a lens and a lens controller, an image pickup processing unit102, an A/D converter103, a camera signal processing unit104, a video signal processing unit105, a D/A converter106, an analog video signal output unit107, a display unit108, a data bus109, a memory110, a memory controller111, a CPU112, a disk unit113, an electric power unit114such as a battery, and an operation unit115including, e.g., a power switch and a recording trigger switch. For the sake of simplicity, the electric power unit114is connected only to the CPU112in FIG.1. In reality, however, electric power is supplied to all units requiring power via power lines.

In this recording/playback apparatus100, the optical system101including a lens performs iris control, focusing control, zoom control, and the like. The image pickup processing unit102photoelectrically converts an object image (not shown) by a CCD (Charge-Coupled Device) or the like. The A/D converter103converts the obtained analog image signal into a digital signal. The camera signal processing unit104performs predetermined data processing such as gamma correction and white balance adjustment for the digital image data.

In recording operation, the video signal processing unit105segments the output image data from the camera signal processing unit104into a plurality of blocks each composed of a plurality of pixels, performs orthogonal transformation such as DCT for each block, and quantizes and encodes the blocks. Generally, a change between two continuous frames is small in motion image data, so an image of interest has high correlations with images before and after that image. By using this characteristic, the differences between an image of interest and images of frames before and after the image of interest are encoded to perform image compression. An MPEG scheme is used most frequently by which the difference between images is obtained after motion compensation is performed to reduce the redundancy in the time axis, and orthogonal transformation such as DCT and variable-length coding are performed on the obtained differential data.

The image data compressed and encoded by the video signal processing unit105is output to the disk unit113and recorded on a magnetooptical disk, as will be described later.

In playback operation, image data reproduced by the disk unit113is output to the video signal processing unit105. The video signal processing unit105performs decoding, which is the reverse of encoding performed during recording, for the reproduced image data to expand its information amount, and outputs the decoded data to the D/A converter106.

The D/A converter106converts the output digital video signal from the video signal processing unit105into an analog signal. The video signal output unit107converts this analog signal into a signal following a television system, such as NTSC or PAL, and outputs the signal. The display unit108is, e.g., a viewfinder or a liquid crystal monitor and allows a user to monitor an image currently being picked up, or a reproduced image, on the basis of the output analog video signal from the D/A converter106.

The CPU112controls the operation of the whole recording/playback apparatus100via the data bus109. The CPU112also controls parameters in the image pickup processing unit102, the camera signal processing unit104, and the video signal processing unit105. The memory control unit111controls data write to and read from the memory110in accordance with a control signal from the CPU112.

The arrangement of the disk unit113will be described below with reference to FIG.2.

FIG. 2is a block diagram showing the arrangement of the disk unit113.

Referring toFIG. 2, this disk unit113includes a magnetooptical disk201, a magnetic head202, a driver203of the magnetic head, an optical pickup214, and a preamplifier205.

A disk motor208rotates the disk201. A thread mechanism210moves the magnetic head202and the optical pickup214in the radial direction of the disk.

In recording operation, this optical pickup214irradiates the disk201with a laser beam emitted from a semiconductor laser element (not shown) such as a laser diode. At the same time, an encoder204performs error correction encoding and channel encoding such as digital modulation for video data input via an interface207. The driver203drives the magnetic head202with a driving signal modulated on the basis of the data processed by the encoder204. In accordance with this modulated driving signal, the magnetic head202records the data by performing magnetic field modulation on the disk201.

In playback operation, the pickup214irradiates the disk201with a laser beam emitted from the semiconductor laser element (not shown), detects the polarized light amount of reflected light caused by the magnetic Kerr effect, and supplies the detected amount to the preamplifier205. The output signal from the preamplifier205is subjected to demodulation and error correction decoding by a decoder206, and output to the video signal processing unit105shown inFIG. 1via the interface207.

A DC motor211drives the thread mechanism210. A servo digital signal processor (DSP)213controls the rotational speed of the disk and servo operations of the thread mechanism210by using a motor driver209and a servo driver212. More specifically, the servo DSP213controls, e.g., rotational servo of the disk and focusing servo, tracking servo, and seek servo of the pickup system.

The bus I/F207exchanges recording/playback data with the data bus109shown in FIG.1. That is, the bus I/F207controls input and output of data with respect to the encoder204during recording and controls input and output of data with respect to the decoder206during playback.

A file (TOC data) structure used in this embodiment will be described below.

First, TOC data processing by the CPU112will be explained.

In this embodiment, as shown inFIG. 9, an inner peripheral portion901of a disk is used as a system management area, and TOC data is recorded in this system management area901. Video and audio data are recorded in a video recording area902.

The CPU112writes TOC data, which is read out from a disk by the disk unit113, into the memory110via the memory control unit111. In this state, the CPU112updates the TOC data stored in the memory110in accordance with a recording or playback operation. When recording is stopped by the recording trigger switch or when the disk is to be ejected, the CPU112records the TOC data in the system management area901.

FIG. 3shows the file directory structure of the recording/playback apparatus100. Referring toFIG. 3, a disk medium301is defined as uppermost hierarchy0. In lower hierarchy1, application attributions such as video302, audio303, a still image304, . . . , can be classified. In lower hierarchy2of any file (inFIG. 3, the video302) defined in hierarchy1, video A305, video B306, video C307, . . . , can be classified in accordance with the dates of image pickup. Subsequently, in lower hierarchy3of any file (inFIG. 3, the video A305) defined in hierarchy2, scene1(308), scene2(309), scene3(310), . . . , partitioned by ON/OFF of the trigger pointer can be classified. Furthermore, in lower hierarchy4of any file (inFIG. 3, scene1(308)) defined in hierarchy3, an image pickup start pointer311(address information), an image pickup end pointer312(address information), a link pointer313(address information) which allows jump during editing and playback, . . . , of scene1can be classified.

Details of the TOC of the recording/playback apparatus100having this directory structure are shown in FIG.4.FIG. 4depicts the structure of the TOC. This structure is roughly classified into a TOC identification header portion containing all 0s or all 1s, system information, and a management information table portion. For each item, a start pointer401, an attribution402, an end pointer403, and a link pointer404can be defined in units of a few bytes.

As an example, playback control of a file in directory hierarchy3shown inFIG. 3will be explained with reference to FIG.4.

First, playback is started from the address, indicated by a start pointer A of address 0001 in the management information table portion, of the video recording area on a disk medium. After the recorded data is continuously reproduced to an address indicated by an end pointer B, the operation jumps to address AAAA indicated by a link pointer. Subsequently, playback is started from the address, indicated by a start pointer C, of the video recording area on the disk medium. When the recorded data is completely reproduced to an address indicated by an end pointer D, the playback is completed. Link pointer 0000 in address AAAA is an index indicating the end of playback. The playback of image data of each scene is controlled on the basis of attribution information.

In this embodiment, as shown inFIG. 4, a U flag (Urgency Flag) is set in the attribution information402of the system information portion. This U flag is 1-bit digital information used to check whether a TOC recorded in the system management area of a disk is the latest one. The use of this U flag will be described in detail later.

FIG. 5is a view showing the arrangement of the electric power unit114shown in FIG.1. This electric power unit114includes a power reduction detector and monitors and detects a decrease in electric power. Referring toFIG. 5, this electric power unit114comprises a battery501, DC—DC converters502and503, resistors504,505, and506for dividing voltage, and comparators508and509.

Electric power from the battery501is converted into a predetermined voltage by the DC—DC converter502and supplied to each circuit of the recording/playback apparatus100. The DC—DC converter503and the subsequent elements detect power reduction. That is, the output voltage from the DC—DC converter503is divided to obtain a first threshold value (Th1) by the resistors504and505and a second threshold value (Th2) by the resistors506and507. Note that Th1>Th2.

The comparator508compares the battery voltage501with Th1and outputs a binary digital signal indicating the comparison result. On the basis of the output from this comparator508, the CPU112instructs to display a power reduction warning if the battery voltage is equal to or lower than Th1. The comparator509compares the battery voltage501with Th2and outputs a binary digital signal indicating the comparison result. On the basis of the output from this comparator509, the CPU112instructs to shut down the power supply if the battery voltage is equal to or lower than Th2.

A control operation by the CPU112in this embodiment will be described below with reference to FIG.6.FIG. 6is a flow chart for explaining recording and playback of image data and TOC data performed by the CPU112.

First, after power-on in step S601, the CPU112causes the disk unit113to read out TOC data from the system management area901on the disk201and write the TOC data in the memory111. In step S602, the CPU112checks for the U flag of the TOC stored in the memory111. In this embodiment, if the U flag is “0”, this indicates that the TOC is normally recorded in the system management area901of the disk201when the last image data is recorded; if the U flag is “1”, this indicates that the TOC is not normally recorded in the system management area901of the disk201when the last image data is recorded.

If the U flag is “0” in step S602, the CPU112waits for a processing instruction in steps S603and S604. If the processing instruction is other than the start of recording, the CPU112performs corresponding processing in step S605.

If the instruction is the start of recording, in step S606the CPU112sets the U flag of the TOC data stored in the memory111to “1” which indicates that the TOC has not been updated, and causes the disk unit113to record the TOC data having this U flag “1” in the system management area901of the disk201. After that, the CPU112performs recording processing in step S607and at the same time always checks for the result of monitoring by the power reduction detector of the electric power unit114in step S608.

If the CPU112detects in step S608that the battery power lowers and the voltage is below the predetermined voltage Th1, the flow advances to step S612, and the CPU112stops recording the image. In accordance with this recording stop position, in step S613the CPU112updates the contents of the TOC data stored in the memory111, so as to reflect the recording start pointer, end pointer, and link pointer of the image data currently being recorded, thereby urgently removing the TOC information.

In step S613, unlike normal recording processing of TOC data, the TOC data is written following the trailing end of the image data whose recording into the video information recording area902is stopped, without moving the head mechanism of the disk unit113to the system management area901. After performing this TOC data recording processing in step S613, the CPU112waits for the next instruction.

On the other hand, if the battery power is not low in step S608and a recording stop instruction is detected in step S609, in step S610the CPU112updates the contents of the TOC data stored in the memory111, so as to reflect the start pointer, end pointer, and link pointer of the latest recorded image data, and sets the U flag to “0”. In step S611, the CPU112moves the head mechanism to the system management area901and writes the TOC information having the updated contents and the U flag “0” in this system management area901.

If in step S602the U flag is set to “1” indicating that the TOC does not show the latest contents, the flow advances to step S614.

In this case, the TOC recorded in the system management area901has not been updated to the latest information. Therefore, the CPU112sequentially searches the video recording area902of the disk201from a position indicated by the final end pointer of the latest TOC information recorded in the system management area901, and reads out the latest TOC information recorded in the video information recording area902as described previously. In step S615, on the basis of the readout latest TOC information, the CPU112updates the contents of the TOC information stored in the memory111and sets the U flag to “0”. In step S616, the CPU112records this TOC information in the system management area901which is the original recording area of TOC information.

The CPU112continues the above operation until power-off or until the battery voltage becomes lower than Th2and then the comparator509shown inFIG. 5outputs a signal indicating a power-supply voltage drop.

In this embodiment as described above, even when the battery voltage lowers during recording, TOC information reflecting the latest recorded contents can be reliably recorded.

The second embodiment will be described next. A recording/playback apparatus of this embodiment has the same configuration as the image pickup recording/playback apparatus explained with reference toFIGS. 1,2, and5in the first embodiment, so a detailed description thereof will be omitted.

In the second embodiment, a TOC is constructed as shown in FIG.7. One-bit remove information indicating that this TOC information is not normally recorded and its contents do not reflect the latest recorded contents can be described in the MSBs of attribution data402′ in a management information table portion.

Processing by a CPU112in this embodiment will be described below with reference to a flow chart in FIG.8.

First, after power-on in step S801, the CPU112causes a disk unit113to read out TOC data from a system management area901on a disk201and write the TOC data in a memory111. In step S802, the CPU112checks for all MSBs in the attributions402′ of the TOC stored in the memory111. In this embodiment, if the MSB of the attribution402′ is “0”, this indicates that the TOC is normally recorded in the system management area901of the disk201when the last image data is recorded; if the MSB is “1”, this indicates that the TOC is not normally recorded in the system management area901of the disk201when the last image data is recorded and that the contents of this TOC do not correspond to the latest recorded contents.

If the MSB of the attribution402′ is “0” in step S802, the CPU112waits for a processing instruction in steps S803and S804. If the processing instruction is other than the start of recording, the CPU112performs corresponding processing in step S805.

If the instruction is the start of recording, in step S806the CPU112sets the MSB of the attribution402′ of the TOC data stored in the memory111to “1” which indicates that the TOC has not been updated, and causes the disk unit113to record the TOC data having this MSB “1” of the attribution402′ in the system management area901of the disk201. After that, the CPU112performs recording processing in step S807and at the same time always checks for the result of monitoring by a power reduction detector of an electric power unit114in step S808.

If in step S808the CPU112detects the battery supply limit, i.e., detects that the battery voltage is below a predetermined voltage Th1, the flow advances to step S812, and the CPU112stops recording the image. In accordance with this recording stop position, in step S813the CPU112updates the contents of the TOC data stored in the memory111, so as to reflect the recording start pointer, end pointer, and link pointer of the image data currently being recorded, thereby urgently removing the TOC information.

In step S813, unlike normal recording processing of TOC data, the TOC data is written following the trailing end of the image data whose recording into a video information recording area902is stopped, without moving a head mechanism of the disk unit113to the system management area901. After performing this TOC data recording processing in step S813, the CPU112waits for the next instruction.

On the other hand, if the battery power is not low in step S808and a recording stop instruction is detected in step S809, in step S810the CPU112updates the contents of the TOC data stored in the memory111, so as to reflect the start pointer, end pointer, and link pointer of the latest recorded image data, and sets the MSB of the attribution402′ to “0”. In step S811, the CPU112moves the head mechanism to the system management area901and writes the updated TOC information in this system management area901.

If in step S802the MSB of the attribution402′ is set to “1” indicating that the TOC does not show the latest contents, the flow advances to step S814.

In this case, the TOC recorded in the system management area901has not been updated to the latest information. Therefore, the CPU112sequentially searches the video recording area902of the disk201from a position indicated by the final end pointer of the newest TOC information recorded in the system management area901, and reads out the latest TOC information recorded in the video information recording area902as described above. In step S815, on the basis of the readout latest TOC information, the CPU112updates the contents of the TOC information stored in the memory111and sets the MSB of the attribution402′ to “0”. In step S816, the CPU112records this TOC information in the system management area901which is the original recording area of TOC information.

The CPU112continues the above operation until power-off or until the battery voltage becomes lower than Th2and then a comparator509shown inFIG. 5outputs a signal indicating a power-supply voltage drop.

In this embodiment as described above, even when the battery voltage lowers during recording, TOC information reflecting the latest recorded contents can be reliably recorded and reproduced.

In the first and second embodiments, the present invention is applied to the recording/playback apparatus100. However, the present invention is similarly applicable to any apparatus which separately records main information and its management information in separated areas on a recording medium.

The third embodiment of the present invention will be described below with reference the accompanying drawings.

FIG. 10is a block diagram showing a recording apparatus1000according to this embodiment of the present invention.

This recording apparatus1000comprises an image pickup unit1001, a picture rearrangement circuit1002, a switch1003, a subtractor1004, a DCT (Discrete Cosine Transform) circuit1005, a quantization circuit1006, a variable-length encoding circuit1007, an inverse quantization circuit1008, an IDCT (Inverse Discrete Cosine Transform) circuit1009, an adder1010, a motion compensation prediction circuit1011, a switch1012, a buffer1013, a rate control circuit1014, a recording processing circuit1015, a magnetooptical disk1016, a picture change detection circuit1017, a TOC memory1018for storing TOC information, a TOC control circuit1019, and an operation unit1020which includes, e.g., a power switch and a recording trigger switch.

The operation will be described next.

A digital image signal obtained by the image pickup unit1001is input in units of frames to the picture rearrangement circuit1002. This picture rearrangement circuit1002has a memory capable of storing a digital image signal having a plurality of frames. By using this memory, the picture rearrangement circuit1002rearranges frames of the input image signal and outputs the signal.

The operation of the picture rearrangement circuit1002will be explained below with reference to FIG.11.

Referring toFIG. 11, an image signal input in units of frames in the order of a first frame, second frame, third frame, . . . , is output by rearranging these frames in the order of the third frame, first frame, second frame, . . .

The picture rearrangement process shown inFIG. 11is necessary to perform intra-encoding and inter-encoding for an image signal as shown in FIG.12.

The intra-encoding is a method of encoding using only data in one frame and generates an I picture shown in FIG.12. The inter-encoding is a method of encoding also using interframe prediction and generates P and B pictures shown in FIG.12.

The intra-encoding and inter-encoding will be described next.

To perform the intra-encoding, the switch1003is closed to a terminal A. The output image data from the picture rearrangement circuit1002is input to the DCT circuit1005via the switch1003and orthogonally transformed. The quantization circuit1006quantizes the orthogonally transformed image data in accordance with a quantization coefficient determined by the rate control circuit1014. The quantized image data is input to the inverse quantization circuit1008and the variable-length encoding circuit1007.

The output image data from the picture rearrangement circuit1002is also input to the motion compensation prediction circuit1011and the picture change detection circuit1017.

The quantized data is inversely quantized by the inverse quantization circuit1008and subjected to IDCT by the IDCT circuit1009. The switch1012is turned off to supply the image data subjected to IDCT to the motion compensation prediction circuit1011. The motion compensation prediction circuit1011generates and outputs a predictive image for the subsequent inter-encoding.

The quantized data is also input to the variable-length encoding circuit1007where the data is variable-length-encoded. The encoded data is input to the buffer1013. When reaching a certain predetermined data amount, the image data in the buffer1013is output to the recording processing circuit1015. This recording processing circuit1015has an arrangement as shown in FIG.2and records the data on the magnetooptical disk1016. The recording processing circuit1015can record data at a higher data rate than the rate of image data input to the buffer1013. In practice, the recording processing circuit1015intermittently reads out data in units of predetermined amounts of data from the buffer1013and records the readout data.

To perform the inter-encoding, the switch1003is closed to a terminal B. The subtractor1004is used to lower the redundancy in the time axis. This subtractor1004outputs the difference between the output image data from the picture rearrangement circuit1002and the predictive image data from the motion compensation prediction circuit1011to the terminal B of the switch1003.

The output data from the subtractor1004is input to the DCT circuit1005via the switch1003and orthogonally transformed. The quantization circuit1006quantizes the orthogonally transformed image data in accordance with a quantization coefficient determined by the rate control circuit1014. The quantized image data is input to the inverse quantization circuit1008and the variable-length encoding circuit1007.

The output image data from the picture rearrangement circuit1002is also input to the motion compensation prediction circuit1011and the picture change detection circuit1017.

The quantized data is inversely quantized by the inverse quantization circuit1008and subjected to IDCT by the IDCT circuit1009. In this inter-encoding, the switch114is turned on to allow the adder1010to add the image data from the IDCT circuit1009and the predictive image data from the motion compensation prediction circuit1011, thereby obtaining decoded image data. This decoded image data is input to the motion compensation prediction circuit1011for the subsequent image encoding. The motion compensation prediction circuit1011outputs predictive image data and a motion vector. This motion vector is input to the variable-length encoding circuit1007.

The quantized data is input to the variable-length encoding circuit1007where the data is variable-length-encoded. The encoded data is input to the buffer1013. When reaching a certain predetermined data amount, the image data in the buffer1013is output to the recording processing circuit1015. The recording processing circuit1015records the image data on the disk1016.

Recording of a TOC as index information in this embodiment will be described below.

Also in this embodiment, TOC information is recorded in a system management area901on a disk shown in FIG.9.

When the power supply is turned on by the operation unit1020, the TOC control circuit1019stores TOC information, read out from the system management area on the disk1016by the recording processing circuit1015, in the TOC memory1018. In accordance with recording processing, the TOC control circuit1019updates the contents of the TOC information stored in the TOC memory1018. When the stop of recording is designated by the operation unit1020, the TOC control circuit1019reads out the latest TOC information stored in the TOC memory1018. The recording processing circuit1015records the readout TOC information in the system management area of the disk1016.

Furthermore, the TOC control circuit1019records the TOC information stored in the TOC memory1018into the disk1016in accordance with an output from the picture change detection circuit1017.

This picture change detection circuit1017reads out image data of a plurality of frames stored in the picture rearrangement circuit1002and calculates a difference A
A=∫|Frame1(Y)−Frame2 (Y)|  (1)
in luminance information between frames. If this difference A is larger than a certain threshold value TH, i.e., if A>TH, the picture change detection circuit1017outputs a control signal indicating a picture change to the TOC control circuit1019.

When detecting this control signal, the TOC control circuit1019controls the TOC memory1018to record TOC information which reflects the contents of recording up to the point, in the system management area of the disk1016by the recording processing circuit1015, by using a period during which no image data is recorded.

FIGS. 13 and 14are views for explaining TOC recording timings.

Symbols ★ inFIG. 13indicate timings at which the picture change detection circuit1017detects a large picture change.

Referring toFIG. 13, in scene1, TOC information is recorded in the system management area at the timings of detection of picture change1301, temporary stop1302, and stop of recording1303.

As described earlier, image data is output to the recording processing circuit1015via the buffer1013. Also, the recording processing circuit1015can record data on the disk1016at a higher rate than the data rate of image data input to the buffer1013.

That is, the recording processing circuit1015performs intermittent recording on the disk1016. As shown inFIG. 14, therefore, non-record periods are produced during recording of image data.FIG. 14shows recording periods1401and data non-record periods1402. Accordingly, when a picture change is detected at timing1401a, TOC information can be recorded, even during image data recording, by moving the head to the system management area in a data non-record period1402a.

Also, in scene1ofFIG. 13, recording is normally stopped at timing1303. Hence, TOC information reflecting data recorded up to this stop of recording1303is recorded in the disk1016. So, all recorded data up to1303can be correctly reproduced.

In scene2, TOC information is recorded in the system management area at picture change detection timings1304and1305. In this example, the power supply is shut down at timing1306before recording stop operation, so recording is not normally stopped. However, TOC information is recorded on the disk1016at the timing1305at which a picture change is detected. The TOC information recorded at this timing1305reflects the contents of image data recorded up to1305. In playback, therefore, data from the start of recording of scene2to the timing1305at which a picture change is lastly detected can be correctly reproduced.

In this embodiment, a picture change is detected by the difference between frames. However, a picture change can also be detected by another method.

For example, as shown inFIGS. 15A and 15B, a histogram of the directions of motion vectors calculated by the motion compensation prediction circuit113is obtained in one frame. If the correlation between the motion vectors in one frame is low, a picture change is detected.

Referring toFIG. 15A, motion vectors having angles of 0 to 90° is largest in number, so changes between pictures are obviously small. Referring toFIG. 15B, the angles of motion vectors evenly distribute in all directions, so changes between pictures are obviously large.

A recording apparatus according to the fourth embodiment of the present invention will be described below.

FIG. 16is a block diagram showing the configuration of a recording apparatus1000of this embodiment. The same reference numerals as in the configuration shown inFIG. 10denote the same parts, and a detailed description thereof will be omitted.

This apparatus shown inFIG. 16includes an audio input unit1021, an audio change detection circuit1022, an audio encoding circuit1023, a buffer1024, and a multiplexer1025.

Encoding of image data inFIG. 16is the same as the apparatus shown inFIG. 10, so a detailed description thereof will be omitted. Encoded image data stored in the buffer1013is multiplexed with audio data by the multiplexer1025and output to a recording processing circuit1015.

The audio input unit1021includes an audio input device such as a microphone and outputs a digital audio signal pertaining to an object to the audio change detection circuit1022and the audio encoding circuit1023. The audio encoding circuit1023encodes this audio data by using a known coding scheme and outputs the encoded image data to the buffer1024. The multiplexer1025multiplexes the image data stored in the buffer1013and the audio data stored in the buffer1024such that pictures and audio are synchronized. The multiplexed data is output to the recording processing circuit1015.

Recording of a TOC as an important point of the present invention will be described next.

Also in this embodiment, TOC information is recorded in a system management area901on a disk shown in FIG.9.

When the power supply is turned on by an operation unit1020, a TOC control circuit1019stores TOC information read out from the system management area on a disk1016by the recording processing circuit1015, in a TOC memory1018. In accordance with recording processing, the TOC control circuit1019updates the contents of the TOC information stored in the TOC memory1018. When the stop of recording is designated by the operation unit1020, the TOC control circuit1019reads out the newest TOC information stored in the TOC memory1018. The recording processing circuit1015records the readout TOC information in the system management area of the disk1016.

In this embodiment, the TOC control circuit1019further records the TOC information stored in the TOC memory1018into the disk1016in accordance with an output from the audio change detection circuit1022.

This audio change detection circuit1022has a comparator and, as shown inFIG. 17, outputs a high-level signal to the TOC control circuit1019when a period during which the level of an input audio signal is lower than a predetermined threshold Ath continues for a predetermined time Tth or more. When the audio change detection circuit1022outputs this high-level control signal, the TOC control circuit1019controls the TOC memory1018to record TOC information which reflects the contents of recording up to the point, in the system management area of the disk1016by the recording processing circuit1015, by using a period during which neither image data nor audio data are recorded.

FIG. 18is a view for explaining TOC recording timings.

Symbols ★ inFIG. 18indicate timings at which the audio change detection circuit1022outputs a control signal indicating that a period in which the input audio level is lower than the threshold value is detected. In scene1, TOC information is recorded in the system management area901of the disk1016at the timings of audio change detection1801, temporary stop1802, and stop of recording1803.

Also in this embodiment, image data is output to the recording processing circuit1015via a buffer1013. Also, the recording processing circuit1015can record data on the disk1016at a higher rate than the data rate of image data input to the buffer1013.

That is, the recording processing circuit1015performs intermittent recording on the disk1016. As shown inFIG. 14, therefore, non-record periods are produced during recording of image data.FIG. 14shows recording periods1401and data non-record periods1402. Accordingly, when a picture change is detected at timing1401a, TOC information can be recorded, even during image data recording, by moving the head to the system management area901in a data non-record period1402a.

Also, in scene1ofFIG. 18, recording is normally stopped at timing1803. Hence, TOC information reflecting data recorded up to this stop of recording1803is recorded in the disk1016. So, all recorded data up to1803can be correctly reproduced.

In scene2, TOC information can be recorded in the system management area on the disk1016at audio change detection timings1804and1805. In this example, the power supply is shut down at timing1806before recording stop operation, so recording is not normally stopped.

In this embodiment, however, TOC information reflecting the contents of recording up to the point is recorded on the disk1016at the timing1805at which an audio change is detected. Therefore, data from the start of recording of scene2to the timing1805at which an audio change is lastly detected can be correctly reproduced.

FIG. 19is a block diagram showing the configuration of a recording apparatus1000according to this embodiment. The same reference numerals as in the configurations shown inFIGS. 10 and 16denote the same parts, and a detailed description thereof will be omitted.

The recording apparatus of this embodiment further comprises a system control circuit1026for controlling the overall operation of the apparatus1000, a still image encoding circuit1027, a buffer1028for still image signals, and a buffer1029for TOC information.

Referring toFIG. 19, the system control circuit1026controls the operation of each unit of the apparatus. That is, in accordance with instructions from an operation unit1020, the system control circuit1026controls a picture rearrangement circuit1002, switches1003and1012, and the still image encoding circuit1027.

First, the operation of normal motion image recording will be described below.

When the start of motion image recording is designated by the operation unit1020, the system control circuit1026controls a picture rearrangement circuit1022to rearrange frames of an image signal from an image pickup unit1001as shown inFIG. 11, and outputs the signal to a switch1003, a subtractor1004and a motion compensation prediction circuit1011. After that, this motion image signal is encoded as described earlier by, e.g., a DCT circuit1005, a quantization circuit1006, a variable-length encoding circuit1007, an inverse quantization circuit1008, an IDCT circuit1009, an adder1010, and the motion compensation prediction circuit1011. The encoded signal is output to a buffer1013.

Also, an input audio signal from an audio input unit1021is encoded by an audio encoding circuit1023and output to a buffer1024.

The operation of still image recording will be described next.

The recording apparatus of this embodiment has a still image recording mode. When still image recording is designated by the operation unit1020during recording of a motion image signal, a still image signal can be recorded on a disk1016independently of the motion image signal.

When the operation unit1020designates still image recording, the system control circuit1026outputs a control signal to the picture rearrangement circuit1022to extract image data of a frame, at the timing corresponding to the still image recording instruction, from an image signal having a plurality of frames output from the image pickup unit1001. The extracted image signal is output to the still image encoding circuit1027.

In accordance with a control signal from the system control circuit1026, the still image encoding circuit1027receives the image data of one frame output from the picture rearrangement circuit1002, encodes the data on the basis of a JPEG standard for still image encoding, and outputs the encoded still image data to the buffer1028. The encoding scheme of this still image encoding circuit107is, of course, not limited to JPEG encoding. For example, base band encoding can also be performed. The still image encoding circuit1027performs real-time processing at a rate of, e.g., 4 Mbits/sec.

Under the control of the system control circuit1026, a multiplexer1025time-divisionally multiplexes the motion image signal and audio signal stored in the buffer1024, the still image signal stored in the buffer1028, and TOC information stored in the buffer1029(as will be described later), and outputs the multiplexed data to a recording processing unit1015. The recording processing unit1015records this multiplexed data in the magnetooptical disk1016.

FIG. 20is a view showing recording areas of TOC data, motion image audio data, and still image data on the disk1016according to this embodiment.

Referring toFIG. 20, TOC data is recorded in a TOC recording area901in the innermost peripheral portion as in FIG.9. In this embodiment, a video recording area is divided into a motion image recording area902A and a still image recording area902B. That is, still image data is recorded in the still image recording area902B outside the TOC recording area901. Motion image audio data is recorded in the motion image-audio recording area902A outside the still image recording area902B.

The still image recording area902B and the motion image-audio recording area902A are segmented into sectors toward the outer periphery, and these sectors are assigned sector numbers in order. Each sector is referred to by the start address, end address, and the like in TOC data.

As shown inFIG. 21, the recording processing circuit1015records variable-length motion image data in units of GOP and fixed-length audio data in a time series manner in the motion image recording area902A on the disk1016. In encoding of MPEG2, a plurality of frames between two I pictures are called 1GOP (Group Of Pictures) and used as a unit of encoding. Usually, 1GOP is composed of 15 frames.

When still image data is stored in the buffer1028in response to a still image recording instruction, the system control circuit1026controls the multiplexer1025to read out this still image data stored in the buffer1028by using a period during which recording of motion image data and audio data on the disk1016is stopped, i.e., a period1401shown in FIG.14. The readout still image data is recorded in the still image recording area902B different from the motion image recording area902A on the disk1016.

TOC data in this embodiment will be described below.

FIG. 22is a view showing the contents of TOC data according to this embodiment.

The TOC of this embodiment has a scene table2201and a contents table2202. The scene table2201shows the order of scenes and the correspondence between each scene and a row in the contents table2202. In playback, scenes are usually reproduced in the order in this scene table2201.

Also, the scene table2201can manage 4,095 scenes, and each scene has a 12-bit pointer which indicates a specific row in the contents table2202. This scene table2201is used in order from 1, and a pointer having no corresponding scene has “0” which indicates the end.

The contents table2202has 4,095 rows, and each row has a start address2203, an end address2204, a link pointer2205, and an attribution2206. The start address2203and the end address2204are composed of 20 bits each and have the start and end addresses, respectively, of a corresponding scene.

The link pointer2205has a pointer indicating the row of the continuation of a scene, when a certain scene is connected to another scene to form one scene or when one scene is dispersedly recorded in discontinuous areas owing to the locations of empty areas. As indicated by an arrow inFIG. 22, when the continuation of a scene shown in row1of the contents table2202is shown in row3, “3” is stored in the link pointer2205of row1to hold the continuity of the scene.

The attribution2206stores data indicating an attribution such as motion image, still image, or copy inhibition.

Data to be processed is, of course, not restricted to motion image-audio data and still image data but can be script data and the like. The type of data can be described in the attribution2206of the TOC data.

A summary of updating of TOC data as management information in the present invention will be explained below. Details will be described later.

When the power supply is turned on, only TOC data is reproduced from the TOC recording area901on a recording medium and stored in the TOC memory1018. The system control circuit1026can instantly know which data is stored in which area on the disk1016at present by referring to the TOC data loaded into the TOC memory1018. To record a motion image and a still image, therefore, the system control circuit1026so controls as to record new data by designating an empty area on the basis of the TOC.

In this embodiment, whenever the operation unit1020designates still image recording, the system control circuit1026updates the TOC data stored in the TOC memory1018to have contents recorded up to that point, i.e., to have contents reflecting all pieces of information concerning motion image data recorded up to that point and still image data to be recorded henceforth.

The system control circuit1026outputs the TOC data having the updated contents to the buffer1029and records the still image data, stored in the buffer1028, into the still image recording area902B on the disk at the aforementioned timing. Subsequently, the system control circuit1026reads out the TOC data stored in the buffer1029and records the readout TOC data in the system management area901on the disk1016. Also in this embodiment, whenever the operation unit1020designates the start and end of normal motion image recording, the system control circuit1026updates the contents of the TOC data, supplies the updated TOC data from the TOC memory1018to the buffer1029, and records the TOC data in the system management area901on the disk1016.

Still image recording can be designated even while no motion image is being recorded. Also in this case, TOC data is updated and recorded on the disk1016.

In this embodiment as described above, when recording of a still image is instructed while a motion image is being recorded, TOC data reflecting recorded contents is recorded on a disk at that time.

During image pickup of one scene, therefore, even when abnormality such as a decrease in remaining battery amount occurs and recording of a motion image is not normally terminated, if still image recording is designated at least once while a motion image is being picked up, TOC data reflecting recorded contents up to that point the still image data is recorded can be recorded on a disk.

Accordingly, the motion image data, audio data, and still image data recorded up to that point can be correctly reproduced.

The present invention can be applied to a system constituted by a plurality of devices or an apparatus comprising a single device.

Further, the objects of the present invention can also be achieved by supplying a storage medium (or a recording medium) recording program codes of software for realizing the functions of the above-mentioned embodiments to a system or an apparatus, and allowing a computer (e.g., a CPU or MPU) of the system or the apparatus to read out and execute the program codes stored in the storage medium. In this case, the program codes themselves read out from the storage medium realize the functions of the above embodiments, and the storage medium storing the program codes constitutes the invention. Furthermore, besides the functions of the above embodiments are realized by executing readout program codes by a computer, the present invention includes a case where an OS (Operating System) or the like running on the computer executes a part or the whole of actual processing on the basis of instructions by the program codes, and the functions of the embodiments are achieved by the processing.

The present invention also includes a case where, after the program codes read out from the storage medium are written in a memory of a function extension board inserted into a computer or of a function extension unit connected to the computer, a CPU or the like of the function extension board or function extension unit performs a part or the whole of actual processing on the basis of instructions by the program codes, and the functions of the above embodiments are accomplished by the processing.