JP4120056B2 - Playback apparatus and playback method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a playback apparatus and playback method for playing back encoded data compressed by the MPEG method or the like, and more particularly to a backward playback technique in such a playback apparatus and playback method.
[0002]
[Prior art]
As a method for compressing video data over a plurality of frames, there is a method for compressing the data amount by recording the difference from the preceding and succeeding frames by using the correlation in the time axis direction over a plurality of frames. However, when only the differential data is always recorded, there is a problem that reproduction can always be performed only from the beginning of the data.
[0003]
Therefore, normally, an intra-frame predictive coding screen in which coding is completed only within the frame without taking correlation with the preceding and following frames is periodically inserted. That is, when compressing video data using correlation in the time axis direction over a plurality of frames, the video data is compressed in units of a screen group structure including at least one intra-frame predictive encoding screen. To do.
[0004]
Note that such a screen group structure is also adopted in the MPEG system widely used as a video data compression system. In the MPEG system, such a screen group structure is referred to as GOP (Group Of Pictures). ing.
[0005]
[Problems to be solved by the invention]
By the way, when the encoded data having such a structure is reproduced in the direction opposite to the time axis direction, first, the encoded data of the screen to be reproduced is first decoded, and then temporally. The encoded data of the previous screen is decoded, and thereafter the encoded data of the previous screen is sequentially decoded in the same manner.
[0006]
At this time, in order to decode the encoded data of the playback target screen, it is necessary to start decoding from the intra-frame predictive encoding screen ahead of the encoded data of the playback target screen. In other words, when decoding the encoded data of the playback target screen, it sequentially decodes from the intra-frame predictive encoding screen ahead of the playback target screen to the playback target screen without output to the outside, When decoding progresses to the playback target screen, the decoded data of the playback target screen is output. When reverse playback is performed, the decoding from the intra-frame predictive coding screen to the playback target screen as described above is repeated every time one screen is played.
[0007]
As described above, when performing reverse playback, it is necessary to repeatedly perform decoding from the intra-frame predictive encoding screen to the playback target screen every time one screen is played back. In performing reverse reproduction by reading data, in order to perform the reverse reproduction at high speed, it is necessary to repeatedly read out the encoded data from the recording medium at high speed.
[0008]
As a recording medium for recording video data, a disk-shaped recording medium or a tape-shaped recording medium is often used, but there is a limit to reading data from such a recording medium at high speed. For this reason, conventionally, it has been difficult to perform backward reproduction at a high speed, which requires repeated reading of encoded data.
[0009]
The present invention has been proposed in view of the conventional situation as described above, and is a reproduction apparatus capable of performing reverse reproduction of encoded data obtained by compressing video data by the MPEG method or the like at higher speed. And a reproduction method.
[0010]
[Means for Solving the Problems]
The playback apparatus according to the present invention uses, as a unit, a screen group structure in which encoded data obtained by compressing video data using a correlation in the time axis direction over a plurality of frames includes at least one intra-frame prediction encoded screen. Read means for reading the encoded data from the recorded recording medium is provided. The storage unit has a storage capacity equal to or larger than the encoded data of one screen group structure and holds the encoded data read from the recording medium by the reading unit. When the encoded data recorded on the recording medium is reproduced in the direction opposite to the time axis direction, the encoded data of the screen group structure including the screen to be reproduced is read by the reading means, and the encoded data is read. Is stored in the storage means, and the encoded data already read by the reading means and held in the storage means is held in the storage means when necessary for decoding processing for backward reproduction. The encoded data is read and decoded.
[0011]
  The storage means isWhen the encoded data that has been held is no longer needed due to the completion of the decoding process during reverse playback, the areas where the encoded data that has become unnecessary are released are sequentially released as free areas.To do.In addition, when the reading means performs backward reproduction, if there is an empty area in the storage means, it reads out the next necessary encoded data and sequentially stores the encoded data in the empty area of the storage means. StoreGo.
[0012]
In the playback device according to the present invention as described above, at the time of backward playback, the encoded data of the screen group structure including the screen to be played back is read by the reading unit, and the encoded data is held in the storage unit, When the encoded data already read by the reading means and held in the storage means is necessary for the decoding process for backward reproduction, the encoded data held in the storage means is read and decoded. I am doing so. Therefore, backward reproduction can be performed without repeatedly reading the same encoded data from the recording medium.
[0013]
On the other hand, in the reproduction method according to the present invention, encoded data obtained by compressing video data using a correlation in the time axis direction over a plurality of frames has a screen group structure in which at least one intra-frame predictive encoded screen is included. When the encoded data is read from the recording medium recorded as a unit and reproduced in the direction opposite to the time axis direction, the encoded data of the screen group structure including the screen to be reproduced is read and the encoded data Are stored in storage means having a storage capacity equal to or larger than the encoded data of one screen group structure. When the encoded data already read and held in the storage means is necessary for the decoding process for backward reproduction, the encoded data held in the storage means is read and decoded.
[0014]
  Reverse playbackWhen the encoded data held by the storage means becomes unnecessary due to the completion of the decoding process, the areas where the unnecessary encoded data are held are sequentially released to be free areas.To do.Also, when performing reverse playback, if there is an empty area in the storage means, the next required encoded data is read and the encoded data is sequentially stored in the empty area of the storage means.Go.
[0015]
In the playback method according to the present invention as described above, at the time of reverse playback, the encoded data of the screen group structure including the screen to be played back is read out, the encoded data is held in the storage means, and already read out. When the encoded data held in the storage means is necessary for the decoding process for backward reproduction, the encoded data held in the storage means is read and decoded. Therefore, backward reproduction can be performed without repeatedly reading the same encoded data from the recording medium.
[0016]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, a case where the present invention is applied to a DVD reproducing apparatus that reproduces video data and the like from a DVD that is put into practical use as an optical disk on which video data and the like are recorded will be described as an example.
[0017]
A configuration example of a DVD playback apparatus to which the present invention is applied is shown in FIG. The DVD reproducing apparatus 1 includes a pickup 2 that reproduces an RF signal from a recording medium (DVD) 100, an RF circuit 3 that is supplied with the RF signal reproduced by the pickup 2 and performs binarization processing on the RF signal, and the like. A data decoder 4 which is supplied with reproduction data from the RF circuit 3 and performs decoding processing such as error correction, a ring buffer memory 20 which temporarily holds the reproduction data decoded by the data decoder 4, and a data decoder 4 includes a demultiplexer 5 that distributes the reproduction data subjected to the decoding process 4 into main video compression data, sub-video compression data, and audio compression data.
[0018]
Also, the DVD playback device 1 decodes the main video compressed data output from the demultiplexer 5 and the sub decoder for decoding the sub video compressed data output from the demultiplexer 5 and combining it with the main video data. A video decoder 7 and an audio decoder 8 for decoding the audio compression data output from the demultiplexer 5 are provided.
[0019]
Also, the DVD playback apparatus 1 is supplied with video data obtained by combining the sub video data from the sub video decoder 7 and the main video data from the video decoder 6, and converts the video data into an NTSC signal or a PAL signal. Digital / NTSC, PAL conversion circuit (hereinafter simply referred to as NTSC conversion circuit) 9. The NTSC signal or PAL signal from the NTSC conversion circuit 9 output from the DVD playback apparatus 1 is input to the monitor 200 and imaged.
[0020]
Further, the DVD playback apparatus 1 includes a digital / analog conversion circuit (hereinafter simply referred to as an A / D conversion circuit) 10 that is supplied with audio data from the audio decoder 8 and converts the audio data into an analog signal.
[0021]
Further, the DVD playback apparatus 1 controls the pickup 2, the RF circuit 3, the data decoder 4, the demultiplexer 5, the video decoder 6, the sub-picture decoder 7, the audio decoder 8, the NTSC conversion circuit 9, and the A / D conversion circuit 10. A controller 11, a user interface 12 that mediates the controller 11 and user operation input, and a memory 13 that serves as a data storage unit of the controller 11 are provided.
[0022]
Note that, in the recording medium 100 to be reproduced by the DVD reproducing apparatus 1, encoded data that has been subjected to image compression processing by the MPEG method is stored in a Video Object Set (in accordance with the DVD format as shown in FIG. (Hereinafter referred to as VOBS)). That is, for example, one movie movie is recorded as one VOBS on the recording medium 100.
[0023]
A VOBS is composed of a plurality of video objects (hereinafter referred to as VOB), and the VOB is composed of a plurality of cells. Cell is a unit of one scene in a movie, for example. The Cell is composed of a plurality of Video Object Units (hereinafter referred to as VOBU).
[0024]
The VOBU is composed of navigation data, main video compression data, sub-video compression data, and audio compression data. The DVD employs the MPEG method for compressing the main video data, and the main video compressed data included in one VOBU is composed of one or more GOPs.
[0025]
The navigation data, main video compression data, sub-video compression data, and audio compression data constituting the VOBU are a navigation pack (NV_PCK), a main video pack (V_PCK), a sub-video pack (SP_PCK), and an audio pack (A_PCK), respectively. It is recorded in a pack.
[0026]
Here, the navigation data is data in which information related to data in the VOBU, information for special reproduction, and the like are recorded. The main video compression data is data that becomes a main video such as a movie, and constitutes a video stream in the DVD format. The sub-picture compressed data is data such as subtitles and constitutes a sub-picture stream in the DVD format. The audio compression data is data relating to audio and constitutes an audio stream in the DVD format.
[0027]
The recording medium 100 on which data is recorded according to such a DVD format is read by the pickup 2 of the DVD playback apparatus 1. The pickup 2 irradiates the signal recording surface of the recording medium 100 with laser light from a laser light source incorporated in the pickup 2 and receives the reflected light reflected on the signal recording surface. The pickup 2 supplies the RF signal reproduced according to the received light to the RF circuit 3.
[0028]
The RF circuit 3 performs waveform equalization and binarization of the RF signal to generate reproduction data and a synchronization signal thereof. The reproduction data generated by the RF circuit 3 is supplied to the data decoder 4.
[0029]
The data decoder 4 performs decoding processing such as error correction on the reproduction data generated by the RF circuit 3. The reproduced data that has been subjected to decoding processing such as error correction by the data decoder 4 is temporarily held in the ring buffer memory 20, read at an appropriate timing, and supplied to the demultiplexer 5.
[0030]
Here, the ring buffer memory 20 is one that can simultaneously perform writing to an arbitrary location of the ring buffer memory 20 and reading from an arbitrary location of the ring buffer memory 20 independently of each other. The storage capacity of the ring buffer memory 20 is set to be 1 GOP or more. As described above, the GOP is a unit of a screen group structure defined in the MPEG system, and one GOP includes at least one intra-frame predictive coding screen.
[0031]
The demultiplexer 5 divides the reproduction data subjected to decoding processing such as error correction by the data decoder 4 into various packs. That is, the demultiplexer 5 divides the reproduction data into a navigation pack (NV_PCK), a main video pack (V_PCK), a sub video pack (SP_PCK), and an audio pack (A_PCK). Then, the demultiplexer 5 supplies the navigation pack (NV_PCK) to the controller 11 and supplies the other packs to the decoders corresponding to the respective packs.
[0032]
That is, the demultiplexer 5 supplies the main video pack (V_PCK) composed of the main video compressed data to the video decoder 6 and supplies the sub video pack (SP_PCK) composed of the sub video compressed data to the sub video decoder 7 for audio compression. An audio pack (A_PCK) composed of data is supplied to the audio decoder 8.
[0033]
The video decoder 6 decodes the main video compressed data in the main video pack supplied from the demultiplexer 5, and generates main video data obtained by decompressing the main video compressed data by this decoding process. Here, a frame buffer memory 15 necessary for decoding the main video compressed data is added to the video decoder 6, and the video decoder 6 uses this frame buffer memory 15 to convert the main video compressed data. Is decrypted. Then, the video decoder 6 supplies the generated main video data to the sub video decoder 7.
[0034]
The sub video decoder 7 decodes the sub video compressed data in the sub video pack supplied from the demultiplexer 5, and generates sub video data obtained by expanding the sub video compressed data by this decoding processing. The sub video decoder 7 combines the sub video data with the main video data supplied from the video decoder 6 to generate video data. That is, the sub video decoder 7 synthesizes subtitle data or the like reproduced as sub video data with the main video data. Then, the sub video decoder 7 supplies the generated video data to the NTSC conversion circuit 9. If there is no sub-video data, the sub-video decoder 7 supplies the main video data supplied from the video decoder 6 as it is to the NTSC conversion circuit 9 as video data.
[0035]
The NTSC conversion circuit 9 converts the video data from digital data into a television signal such as NTSC or PAL. The television signal from the NTSC conversion circuit 9 is sent to the monitor 200 and is displayed as an image on the monitor 200.
[0036]
The audio decoder 8 decodes the audio compression data in the audio pack supplied from the demultiplexer 5, and generates audio data obtained by decompressing the audio compression data by this decoding processing. Then, the audio decoder 8 supplies the generated audio data to the A / D conversion circuit 10.
[0037]
The A / D conversion circuit 10 converts audio data that is digital data into an analog audio signal and outputs the analog audio signal. By supplying this output to a speaker or the like, the user can hear the sound reproduced from the recording medium 100.
[0038]
The controller 11 operates as described above for the pickup 2, the RF circuit 3, the data decoder 4, the demultiplexer 5, the video decoder 6, the sub-picture decoder 7, the audio decoder 8, the NTSC conversion circuit 9, and the A / D conversion circuit 10. Take control. The controller 11 receives an operation input from a user via a user interface 12 including an operation panel and a remote controller, and the controller 11 controls each circuit based on the operation input.
[0039]
Next, the operation during reverse playback of the DVD playback apparatus 1 as described above will be described.
[0040]
In encoded data compressed using the MPEG method, each GOP has one or more intra-frame predictive encoding screens in which encoding is completed only within the frame without correlation with the preceding and succeeding frames. include. In order to decode the screen to be reproduced, the encoded data is supplied to the video decoder 6 from the GOP including the screen or the head of the previous GOP (hereinafter referred to as the GOP head) and decoded. Can be done.
[0041]
Then, during reverse playback, the screen to be played advances in the reverse direction with respect to the time axis direction. Therefore, at the time of reverse reproduction, first, the encoded data from the GOP head to the first screen to be reproduced is supplied to the video decoder 6 for decoding, and then the second screen to be reproduced from the GOP head ( That is, the encoded data up to the previous screen) is supplied to the video decoder 6 for decoding, and then encoded up to the third playback target screen (ie, the previous screen) from the beginning of the GOP. Data is supplied to the video decoder 6 for decoding. Similarly, the reverse reproduction is realized by sequentially supplying the encoded data from the GOP head to the reproduction target screen to the video decoder 6 for decoding.
[0042]
In the conventional DVD playback apparatus, in order to realize such backward playback, encoded data from the GOP head to the playback target screen is read from the recording medium for each playback target screen. Therefore, the time required for reading the encoded data from the recording medium becomes a bottleneck, and it is difficult to increase the speed of reverse reproduction.
[0043]
On the other hand, in the DVD device 1 to which the present invention is applied, the encoded data required for one decoding process is only a continuous part in the recording medium when performing reverse reproduction, and Considering that the encoded data is often used repeatedly in the decoding process, the encoded data once read from the recording medium 100 is stored in the ring buffer memory 20. When the reverse reproduction is performed and the encoded data that has already been read from the recording medium 100 is repeatedly used for the decoding process, it is not read from the recording medium 100 again but is stored in the ring buffer memory 20. Use encoded data. Thereby, it is not necessary to repeatedly read data from the recording medium 100, and the reverse playback speed can be increased.
[0044]
When performing reverse reproduction using the ring buffer memory 20 as described above, specifically, first, the encoded data required for the reverse reproduction is obtained by using the pickup 2 and the RF circuit as described above. 3. The data decoder 4 is used to read from the recording medium 100 in GOP units, and the encoded data is written to the ring buffer memory 20.
[0045]
Next, among the encoded data written in the ring buffer memory 20, the data necessary for decoding the screen to be reproduced first, that is, the encoded data from the beginning of the GOP to the screen to be reproduced is stored in the ring buffer memory 20. Read from. The encoded data read from the ring buffer memory 20 is sent to the demultiplexer 5 as described above, and thereafter subjected to decoding processing by each decoder.
[0046]
Next, of the encoded data written in the ring buffer memory 20, data necessary for decoding the second screen to be reproduced (that is, the previous screen), that is, from the GOP head to the screen to be reproduced. The encoded data is read from the ring buffer memory 20. The encoded data read from the ring buffer memory 20 is sent to the demultiplexer 5 as described above, and thereafter subjected to decoding processing by each decoder.
[0047]
Then, the reverse reproduction is sequentially advanced by sequentially performing the above processing. At this time, while the encoded data necessary for decoding the screen to be reproduced is read from the ring buffer memory 20 and the decoding process is being performed, the next required encoded data is previously read from the recording medium 100. Then, data is sequentially written into the free area of the ring buffer memory 20. Thus, when it is necessary to send the encoded data necessary for decoding to the demultiplexer 5, the encoded data necessary for decoding is already read from the recording medium 100 and exists in the ring buffer memory 20. deep. Further, when the backward reproduction is sequentially advanced in this way, the area where the encoded data that has become unnecessary after the completion of the reproduction is written out of the storage area of the ring buffer memory 20 is set as an empty area, and the following is performed. Used to capture encoded data.
[0048]
The control process of the ring buffer memory 20 when performing backward reproduction as described above will be described in more detail.
[0049]
The ring buffer memory control process includes a data input control process (FIG. 3) for reading encoded data from the recording medium 100 and writing it to the ring buffer memory 20, and a data output for reading encoded data necessary for decoding from the ring buffer memory 20. It consists of control processing (FIG. 4).
[0050]
In the data input control process, as shown in FIG. 3, first, in step S1-1, it is determined whether there is a free area in the ring buffer memory 20. If there is no free area, the process waits until a free area is generated. On the other hand, if there is a free area, the process proceeds to step S1-2.
[0051]
In step S1-2, the encoded data corresponding to the front of the encoded data on the ring buffer memory 20 is read from the recording medium 100 as much as the free space in the ring buffer memory 20, and the encoded data is read from the free space in the ring buffer memory 20. Write to the area. Then, it returns to step S1-1 and repeats a process.
[0052]
By performing such data input control processing, every time an empty area is generated in the ring buffer memory 20, encoded data necessary for decoding is read from the recording medium 100 and written to the ring buffer memory 20. Become.
[0053]
On the other hand, in the data output control process, as shown in FIG. 4, first, in step S2-1, it is determined whether or not there is a request for instructing to read out and output the encoded data from the ring buffer memory 20. If no encoded data output request is received, the process waits until an encoded data output request is received. On the other hand, if an encoded data output request is received, the process proceeds to step S2-2. .
[0054]
In step S2-2, it is determined whether or not encoded data for which an output request has been received has already been taken into the ring buffer memory 20. If fetching of the encoded data requested to be output has not been completed, the process returns to step S2-1 and is repeated until the encoded data is fetched by the data input control process. On the other hand, if fetching of the encoded data requested to be output has been completed, the process proceeds to step S2-3.
[0055]
In step S2-3, the encoded data requested to be output is output from the ring buffer memory 20. The encoded data output from the ring buffer memory 20 is sent to the demultiplexer 5 as described above, and thereafter subjected to decoding processing by each decoder.
[0056]
Next, in step S2-4, of the storage area of the ring buffer memory 20, an area in which encoded data that has become unnecessary after reproduction is written is set as an empty area. Then, it returns to step S2-1 and repeats a process. If a free space is generated in the ring buffer memory 20 by the process in step S2-4, new encoded data is read from the recording medium 100 by the above-described data input control process, and the encoded data is It is newly written in the ring buffer memory 20.
[0057]
FIG. 5 shows a specific example of how the storage area of the ring buffer memory 20 is used when the ring buffer memory control process as described above is performed. Here, for the sake of convenience, attention is paid only to video data recorded in units of GOP, and description of other data (navigation data, etc.) processing is omitted.
[0058]
First, as shown in FIG. 5A, the recording medium includes an (n−1) th GOP (GOP)._n-1), Nth GOP (GOP_n), N + 1st GOP (GOP_{n + 1}) Is recorded. At this time, GOP_{n + 1}Suppose that reverse playback starts from.
[0059]
At this time, first, as shown in FIG._{n + 1}The encoded data is read as much as an empty area of the ring buffer memory 20 from the end to the start direction, and the read encoded data is written into the ring buffer memory 20. In the example of FIG. 5B, GOP_{n + 1}Encoded data and GOP_{n + 1}The previous GOP (ie GOP_n) Part of the second half of the encoded data is read and written to the ring buffer memory 20.
[0060]
Next, encoded data necessary for decoding the screen to be reproduced is read from the ring buffer memory 20 and sent to the demultiplexer 5. As a result, when there is encoded data that is no longer necessary for the subsequent decoding processing, the storage area of the ring buffer memory 20 in which the encoded data is stored is stored as shown in FIG. Free it up to make it a free area.
[0061]
Next, as shown in FIG. 5 (d), the continuation of the encoded data is read as much as the free area of the ring buffer memory 20, and the encoded data is written into the free area of the ring buffer memory 20. In the example of FIG. 5D, GOP_nA part of the continuation of the encoded data is read and written in the ring buffer memory 20.
[0062]
Next, encoded data necessary for decoding the screen to be reproduced is read from the ring buffer memory 20 and sent to the demultiplexer 5. As a result, when there is encoded data that is no longer necessary for the subsequent decoding processing, the storage area of the ring buffer memory 20 in which the encoded data is stored is stored as shown in FIG. Free it up to make it a free area.
[0063]
Next, as shown in FIG. 5 (f), the continuation of the encoded data is read as much as the free area of the ring buffer memory 20, and the encoded data is written into the free area of the ring buffer memory 20. In the example of FIG. 5 (f), GOP_nThe remaining encoded data and GOP_nThe previous GOP (ie GOP_n-1) In the latter half of the data is read and written to the ring buffer memory 20.
[0064]
In the same manner, the encoded data is read from the ring buffer memory 20, the storage area of the ring buffer memory 20 in which the unnecessary encoded data is stored, and the ring buffer memory which has become a free area. The writing of new encoded data to 20 is sequentially repeated.
[0065]
Here, the ring buffer memory 20 has a storage capacity of 1 GOP or more. In other words, the ring buffer memory 20 has a storage capacity equal to or greater than the maximum value of the data amount required for one decoding. Therefore, by using the ring buffer memory 20 as described above, all the encoded data necessary for one decoding always exists on the ring buffer memory 20. Therefore, by performing reverse reproduction using the ring buffer memory 20 as described above, processing for repeatedly reading the same encoded data from the recording medium 100 in order to decode each screen during reverse reproduction becomes unnecessary. .
[0066]
In the case of performing backward reproduction using the ring buffer memory 20 as described above, the arrangement of encoded data on the recording medium 100 and the code on the ring buffer memory 20 are shown in FIG. The encoded data is written into the ring buffer memory 20 so that the arrangement of the encoded data is the same.
[0067]
That is, each time the encoded data is read from the recording medium 100 and written into the ring buffer memory 20 every time an empty area is generated in the ring buffer memory 20, the encoded data is stored on the ring buffer memory 20. Write continuously. Thereby, the storage area of the ring buffer memory 20 can be utilized very efficiently.
[0068]
In other words, by using the ring buffer memory 20 in this way, the amount of encoded data to be held in the ring buffer memory 20 can be minimized, and only the maximum value of the data amount required for one decoding is obtained. If the storage capacity is sufficient, the requirements for applying the present invention can be satisfied.
[0069]
As described above, by applying the present invention, it is not necessary to repeatedly read out the same data from the recording medium 100 in order to decode each screen during backward reproduction, so that backward reproduction is performed at high speed. Is possible. Furthermore, by devising the order of writing to the ring buffer memory 20 as described above, the storage area can be used efficiently, and the present invention can be realized with a small storage capacity. Furthermore, since many DVD playback apparatuses are originally provided with a ring buffer memory, the amount of change in the apparatus when applying the present invention is small. That is, by applying the present invention, it is possible to increase the reverse playback speed while minimizing the increase in cost.
[0070]
In the above description, an example is given in which processing is performed in units of GOP, which is the minimum unit of the screen group structure including at least one intra-frame prediction encoding screen, but processing is performed in units larger than GOP. Needless to say, you can. That is, for example, the storage capacity of the ring buffer memory 20 may be 1 VOBU or more, and processing may be performed in units of VOBU. Further, for example, the storage capacity of the ring buffer memory 20 may be 1 Cell or more, and Cell Processing may be performed in units of.
[0071]
In the above description, an example in which the ring buffer memory 20 is used as a storage unit that stores encoded data read from the recording medium 100 has been described. If a ring buffer memory is used, the storage area can be used very efficiently as described above. Therefore, the ring buffer memory is very suitable as a storage means for holding encoded data read from a recording medium. However, it is needless to say that the storage means for holding the encoded data read from the recording medium need not be a ring buffer memory if there is sufficient storage capacity.
[0072]
【The invention's effect】
As described above in detail, according to the present invention, it is possible to perform reverse reproduction of encoded data obtained by compressing video data by the MPEG method or the like at higher speed.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration example of a DVD playback apparatus to which the present invention is applied.
FIG. 2 is a diagram showing a data structure of a DVD format.
FIG. 3 is a diagram showing a flow of data input control processing.
FIG. 4 is a diagram showing a flow of data output control processing.
FIG. 5 is a diagram illustrating a specific example of how a storage area of a ring buffer memory is used.
[Explanation of symbols]
1 DVD player, 2 pickup, 3 RF circuit, 4 data decoder, 5 demultiplexer, 6 video decoder, 7 sub-picture decoder, 8 audio decoder, 9 NTSC conversion circuit, 10 D / A conversion circuit, 11 controller, 12 User interface, 13 memory, 15 frame buffer memory, 20 ring buffer memory, 100 recording medium, 200 monitor

Claims (4)

Coded data obtained by compressing video data using a correlation in the time axis direction over a plurality of frames is encoded from a recording medium on which a screen group structure including at least one intra-frame predictive coding screen is recorded as a unit. Reading means for reading the digitized data;
Having a storage capacity equal to or larger than the encoded data of one screen group structure, and storing means for holding encoded data read from the recording medium by the reading means,
When the encoded data recorded on the recording medium is reproduced in the direction opposite to the time axis direction, the encoded data of the screen group structure including the screen to be reproduced is read out by the reading means and the encoded data is stored. If the encoded data that is already read by the reading means and held in the storage means is necessary for the decoding process for backward reproduction, the encoding held in the storage means data have row decoding reads,
When the backward reproduction is performed, the storage means stores the encoded data that is no longer needed when the encoded data that is held becomes unnecessary for the subsequent decoding process due to the completion of the decoding process. The area that had been released is released sequentially to make it an empty area,
When there is an empty area in the storage means, the reading means reads out the encoded data from the unit of the screen structure to be reproduced in the reverse direction next, and sequentially stores the encoded data in the empty area of the storage means. A reproducing apparatus characterized by the above. It said storage means, playback apparatus according to claim 1, characterized in that the ring buffer memory. Coded data obtained by compressing video data using a correlation in the time axis direction over a plurality of frames is encoded from a recording medium on which a screen group structure including at least one intra-frame predictive coding screen is recorded as a unit. When data is read out and played back in the direction opposite to the time axis direction,
Read out the encoded data of the screen group structure including the screen to be reproduced and hold the encoded data in a storage means having a storage capacity equal to or larger than the encoded data of one screen group structure,
If the encoded data stored in the already read and storage means necessary for decoding processing for the reverse reproduction, have row decoding reads the encoded data stored in the storage means,
When the backward reproduction is performed and the encoded data held by the storage unit becomes unnecessary for the subsequent decoding process due to the completion of the decoding process, the unnecessary encoded data is held. Sequentially release the free space to free space,
When there is an empty area in the storage means, the encoded data is read from the unit of the screen structure to be reproduced in the next reverse direction, and the encoded data is sequentially stored in the empty area of the storage means. Playback method. 4. A reproducing method according to claim 3 , wherein a ring buffer memory is used as said storage means.

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