JP2000101970A - Device and method of reproducing - Google Patents

Abstract

PROBLEM TO BE SOLVED: To faster perform backward reproduction of encoded data obtained by compressing video data at higher speed, such as MPEG system. SOLUTION: When backward reproduction is performed, encoded data of a GOP(group of pictures), including an image to be reproduced, are read and the encoded data are stored in a ring buffer memory 20. Then, when encoded data which are already read and stored in the memory 20 are needed for coding processing for backward reproduction, the encoded data stored in the memory 20 are read and decoded.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing apparatus and a reproducing method for reproducing coded data compressed by the MPEG system or the like, and more particularly to a reverse reproducing method in such a reproducing apparatus and reproducing method. About technology.

[0002]

2. Description of the Related Art As a method of compressing video data over a plurality of frames, there is a method of using a correlation in a time axis direction over a plurality of frames and recording a difference between the preceding and succeeding frames to reduce the data amount. However, if only the difference data is always recorded, inconvenience such that the reproduction can always be performed only from the beginning of the data occurs.

Therefore, normally, an intra-frame predictive coded picture in which coding is completed only within a frame without taking a correlation with the preceding and succeeding frames is regularly inserted. That is, when compressing video data using the 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 coding screen. I do.

The MPEG system widely used as a video data compression system also employs such a screen group structure. In the MPEG system, such a screen group structure is referred to as a GOP (Group Of Pictures). ).

[0005]

When the encoded data having such a structure is reproduced in the direction opposite to the time axis, first, the encoded data of the screen to be reproduced is firstly encoded. Decoding is performed, and then, the encoded data of the immediately preceding screen is decoded, and similarly, the encoded data of the immediately preceding screen is sequentially decoded.

At this time, in order to decode the coded data of the playback target screen, it is necessary to start decoding from the intra-frame predictive coded screen located ahead of the coded data of the playback target screen. In other words, when decoding the encoded data of the playback target screen, from the intra-frame predictive encoding screen located ahead of the playback target screen to the playback target screen, sequentially decode without outputting to the outside, When the decoding has progressed to the reproduction target screen, the decoded data of the reproduction target screen is output.
When performing reverse playback, decoding from the intra-frame predictive coding screen to the playback target screen as described above is performed.
It is repeated each time one screen is reproduced.

As described above, when performing reverse reproduction, it is necessary to repeat decoding from the intra-frame predictive coded screen to the reproduction target screen every time one screen is reproduced. When performing reverse reproduction at high speed when reading encoded data that is present and performing reverse reproduction, it is necessary to repeatedly read encoded data from a recording medium at high speed.

As a recording medium on which video data is recorded, 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 high-speed reverse reproduction that requires repeated reading of encoded data.

[0009] The present invention has been proposed in view of the above-mentioned conventional circumstances, and enables faster reverse reproduction of encoded data obtained by compressing video data by the MPEG system or the like. It is an object of the present invention to provide a reproducing apparatus and a reproducing method.

[0010]

According to the present invention, there is provided a reproducing apparatus comprising: a coded data obtained by compressing video data over a plurality of frames using a correlation in a time axis direction; There is provided a reading means for reading encoded data from a recording medium recorded in units of a screen group structure including the number of sheets. Also, a storage unit having a storage capacity equal to or larger than the encoded data of one screen group structure and holding encoded data read from the recording medium by the reading unit is provided. Then, when the encoded data recorded on the recording medium is reproduced in a 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 read out. Is stored in the storage unit, and when the encoded data already read out by the reading unit and stored in the storage unit is necessary for decoding processing for reverse reproduction, the encoded data is stored in the storage unit. The encoded data is read and decoded.

When performing the reverse reproduction, the storage means stores the unnecessary encoded data when the retained encoded data becomes unnecessary due to the completion of the decoding process. It is preferable that the freed area is sequentially released to make it an empty area. Further, when performing reverse reproduction, if there is a free area in the storage means, the reading means reads the next required encoded data and sequentially stores the encoded data in the free area of the storage means. It is preferable to store them.

In the reproducing apparatus according to the present invention as described above,
At the time of reverse reproduction, the coded data of the screen group structure including the screen to be reproduced is read out by the reading means, and the coded data is stored in the storage means. When the coded data used is necessary for decoding processing for reverse reproduction, the coded data stored in the storage means is read and decoded. Therefore, reverse reproduction can be performed without repeatedly reading the same encoded data from the recording medium.

On the other hand, in the reproducing method according to the present invention, the encoded data obtained by compressing the video data over a plurality of frames using the correlation in the time axis direction is converted into a screen including at least one intra-frame predictive encoded screen. When the encoded data is read from the recording medium recorded in units of the group structure and is played back in the reverse direction with respect to the time axis direction, the encoded data of the screen group structure including the screen to be played is read and read. The encoded data is stored in a storage unit having a storage capacity equal to or larger than the encoded data of one screen group structure. Then, 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.

When performing the reverse reproduction, if the encoded data held by the storage means becomes unnecessary due to the completion of the decoding process, the area in which the unnecessary encoded data is held is deleted. It is preferable to release them sequentially to make them empty areas. Also, when performing reverse playback, if there is a free area in the storage means, it is possible to read out the next required coded data and sequentially store the coded data in the free area of the storage means. preferable.

In the reproducing method according to the present invention as described above,
At the time of reverse reproduction, the coded data of the screen group structure including the screen to be reproduced is read out, and the coded data is stored in the storage unit, and the coded data already read out and stored in the storage unit is read out. Is necessary for decoding processing for reverse reproduction, the encoded data stored in the storage means is read and decoded. Therefore, reverse reproduction can be performed without repeatedly reading the same encoded data from the recording medium.

[0016]

Embodiments of the present invention will be described below in detail with reference to the drawings. In the following description, a D that reproduces video data and the like from a DVD that has been put into practical use as an optical disc on which video data and the like are recorded is described.
A case where the present invention is applied to a VD playback device will be described as an example.

FIG. 1 shows an example of the configuration of a DVD reproducing apparatus to which the present invention is applied. The DVD reproducing apparatus 1 includes a pickup 2 that reproduces an RF signal from a recording medium (DVD) 100, and an RF circuit 3 that is supplied with the RF signal reproduced by the pickup 2 and performs a binarization process or the like of the RF signal.
A data decoder 4 supplied with reproduction data from the RF circuit 3 and performing decoding processing such as error correction; a ring buffer memory 20 for temporarily holding the reproduction data decoded by the data decoder 4; A demultiplexer 5 is provided for distributing the reproduced data decoded by the decoder 4 into compressed main video data, compressed sub-video data, and compressed audio data.

The DVD reproducing apparatus 1 further comprises a video decoder 6 for decoding the compressed main video data output from the demultiplexer 5, and a sub video compressed data output from the demultiplexer 5 for decoding the main video data. It comprises a sub-video decoder 7 for synthesizing and an audio decoder 8 for decoding the compressed audio data output from the demultiplexer 5.

The DVD reproducing apparatus 1 is supplied with video data obtained by synthesizing the sub video data from the sub video decoder 7 and the main video data from the video decoder 6.
A digital / NTSC / PAL conversion circuit (hereinafter, simply referred to as an NTSC conversion circuit) 9 for converting the video data into an NTSC signal or a PAL signal is provided. Then, the NTSC signal or PAL signal from the NTSC conversion circuit 9 output from the DVD playback device 1 is input to the monitor 200 and is imaged.

The DVD reproducing apparatus 1 is supplied with audio data from the audio decoder 8, and includes a digital / analog conversion circuit (hereinafter simply referred to as an A / D conversion circuit) 10 for converting the audio data into an analog signal. Prepare.

Further, the DVD reproducing apparatus 1 comprises a pickup 2, an RF circuit 3, a data decoder 4, a demultiplexer 5, a video decoder 6, a sub-picture decoder 7, an audio decoder 8, an NTSC conversion circuit 9, and an A / D conversion circuit 10. , A user interface 12 for mediating the controller 11 and a user's operation input, and a memory 13 serving as a data storage unit of the controller 11.

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 system is stored in a Video format in accordance with the DVD format as shown in FIG. It is recorded in units called Object Set (hereinafter referred to as VOBS). That is, for example, one work of a movie is recorded on the recording medium 100 as one VOBS.

VOBS is composed of a plurality of Video Objects (hereinafter, referred to as "Video Objects").
Called VOB. ), And the VOB is composed of a plurality of C
ell. The 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 VOBUs).

The VOBU is composed of navigation data, main video compression data, sub video compression data, and audio compression data. Note that the DVD adopts the MPEG method for compressing the main video data, and the main video compression data included in one VOBU includes one or more GOPs.

The navigation data, the main video compression data, the sub video compression data, and the audio compression data that constitute the VOBU are respectively stored in the navigation pack (NV
_PCK), a main video pack (V_PCK), a sub video pack (SP_PCK), and an audio pack (A_PCK).

Here, the navigation data is VOB
This is data in which information on data in U, information for special reproduction, and the like are recorded. The compressed main video data is data that becomes a main video such as a movie, and forms a video stream in the DVD format. Also,
The sub-picture compression data is data such as subtitles,
Constructs a sub-picture stream in the format. The audio compression data is data relating to audio, and constitutes an audio stream in the DVD format.

The recording medium 100 on which data is recorded in accordance with the DVD format is a DVD reproducing device 1
The data is read by the pickup 2.
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. Then, the pickup 2 supplies an RF signal reproduced according to the received light to the RF circuit 3.

The RF circuit 3 performs waveform equalization and binarization of the RF signal to generate reproduced data and a synchronization signal thereof. The reproduction data and the like generated by the RF circuit 3 are supplied to a data decoder 4.

The data decoder 4 performs a decoding process such as an error correction on the reproduced data generated by the RF circuit 3. The reproduced data subjected to decoding processing such as error correction by the data decoder 4 is temporarily stored in the ring buffer memory 20, read out at an appropriate timing, and supplied to the demultiplexer 5.

Here, the ring buffer memory 20 has
One that can simultaneously perform writing to an arbitrary location in the ring buffer memory 20 and reading from an arbitrary location in the ring buffer memory 20 independently of each other is used. The storage capacity of the ring buffer memory 20 is set to be equal to or more than 1 GOP. Note that a GOP is a unit of a screen group structure defined in the MPEG system as described above, and one GOP includes at least one intra-frame predictive coded screen.

The demultiplexer 5 includes a data decoder 4
To divide the reproduced data subjected to decoding processing such as error correction into various packs. That is, the demultiplexer 5 converts the reproduced 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,
Other packs are supplied to respective decoders corresponding to the respective packs.

That is, the demultiplexer 5 supplies a main video pack (V_PCK) composed of compressed main video data to the video decoder 6 and supplies a sub video pack (SP_PCK) composed of compressed sub-video data to the sub-picture decoder 7. , An audio pack composed of audio compression data (A_PCK)
Is supplied to the audio decoder 8.

The video decoder 6 includes a demultiplexer 5
The main video compression data in the main video pack supplied from is decoded, and the main video data is generated by expanding the main video compression data. here,
The video decoder 6 is provided with a frame buffer memory 15 necessary for decoding the main video compressed data. The video decoder 6 uses the frame buffer memory 15 to decode the main video compressed data. I do. Then, the video decoder 6 supplies the generated main video data to the sub video decoder 7.

The sub-picture decoder 7 includes a demultiplexer 5
The decoding process of the sub-picture compressed data in the sub-picture pack supplied from is performed, and by this decoding process, the sub-picture data obtained by expanding the sub-picture compressed data is generated. The sub-picture decoder 7 combines this sub-picture data with the main picture data supplied from the video decoder 6 to generate picture data. That is, the sub-picture decoder 7 combines subtitle data and the like reproduced as sub-picture data with main video data. Then, the sub-video decoder 7 supplies the generated video data to the NTSC conversion circuit 9. When there is no sub-video data, the sub-video decoder 7 supplies the main video data supplied from the video decoder 6 to the NTSC conversion circuit 9 as video data as it is.

The NTSC conversion circuit 9 converts 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 displayed on the monitor 200 as an image.

The audio decoder 8 decodes the compressed audio data in the audio pack supplied from the demultiplexer 5, and generates audio data obtained by expanding the compressed audio data by the decoding processing. Then, the audio decoder 8 supplies the generated audio data to the A / D conversion circuit 10.

The A / D conversion circuit 10 converts audio data, which is digital data, into an analog audio signal and outputs it. By supplying this output to a speaker or the like, the user can hear the sound reproduced from the recording medium 100.

The controller 11 includes the pickup 2, R
The above-described operations of the F 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 are controlled. The controller 11
Receives an operation input from a user through a user interface 12 including an operation panel and a remote controller. Based on the operation input, the controller 1
1 controls each circuit.

Next, the operation of the above-described DVD reproducing apparatus 1 at the time of reverse reproduction will be described.

In the coded data compressed by adopting the MPEG system, each GOP has an intra-frame prediction coding screen in which coding is completed only within a frame without correlation with the preceding and following frames. One or more are included.
Then, in order to decode the screen to be played back, the GOP including the screen or the head of the GOP immediately before that (hereinafter, referred to as the GOP)
Called the GOP head. ), The encoded data may be supplied to the video decoder 6 for decoding.

At the time of reverse reproduction, the screen to be reproduced advances in the reverse direction with respect to the time axis direction. Therefore, at the time of reverse reproduction, first, the coded data from the head of the GOP to the screen to be reproduced first is supplied to the video decoder 6 to perform decoding, and then the coded data from the head of the GOP is reproduced.
The coded data up to the screen to be reproduced first (that is, the immediately preceding screen) is supplied to the video decoder 6 for decoding, and then the third screen to be reproduced from the top of the GOP (that is, one more screen) The coded data up to the previous screen is supplied to the video decoder 6 for decoding. In the same manner, in the same manner, the encoded data from the top of the GOP to the screen to be reproduced is sequentially supplied to the video decoder 6 to perform decoding, thereby realizing reverse reproduction.

In the conventional DVD reproducing apparatus, in order to realize such reverse reproduction, the encoded data from the top of the GOP to the reproduction target screen is read from the recording medium for each reproduction target screen. Was. Therefore, the time required to read the encoded data from the recording medium becomes a bottleneck, and it has been difficult to increase the speed of reverse reproduction.

On the other hand, in the DVD apparatus 1 to which the present invention is applied, the coded data required for one decoding process is only a continuous part of the recording medium when performing reverse reproduction. In addition, in view of the fact that the encoded data is often used repeatedly in the decoding process, the recording medium 100
The coded data once read out from is stored in the ring buffer memory 20. When the encoded data that has already been read from the recording medium 100 is to be used repeatedly for decoding when performing reverse reproduction, the encoded data is stored in the ring buffer memory 20 instead of being read from the recording medium 100 again. Use coded data. Accordingly, it is not necessary to repeatedly read data from the recording medium 100, and it is possible to increase the speed of reverse reproduction.

When performing the reverse reproduction using the ring buffer memory 20 as described above, first, first, the coded data which is first required for performing the reverse reproduction is picked up by the pickup 2 as described above. , The RF circuit 3 and the data decoder 4 are used to read data from the recording medium 100 in GOP units, and write the encoded data to the ring buffer memory 20.

Next, of 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 top of the GOP to the screen to be reproduced is stored in a ring. Read from the buffer memory 20. Then, the ring buffer memory 20
Is sent to the demultiplexer 5, as described above, and then subjected to decoding processing and the like by each decoder.

Next, of the encoded data written in the ring buffer memory 20, data necessary for decoding the screen to be reproduced second (that is, the immediately preceding screen), that is, data to be reproduced from the top of the GOP. The coded data up to the screen is read from the ring buffer memory 20. Then, the encoded data read from the ring buffer memory 20 is sent to the demultiplexer 5 as described above, and then subjected to a decoding process or the like by each decoder.

Then, the above-described processing is sequentially performed, whereby the reverse reproduction is sequentially advanced. 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 performed, the encoded data required next is read from the recording medium 100 in advance. Are sequentially written to a 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 stored in the recording medium 10
It is read from 0 and stored in the ring buffer memory 20. When the backward reproduction is sequentially advanced in this manner, an area in the storage area of the ring buffer memory 20 in which encoded data that has become unnecessary after the reproduction has been completed is written as a free area. Used to capture encoded data.

The control processing of the ring buffer memory 20 when performing reverse reproduction as described above will be described in further detail.

The control process of the ring buffer memory is a data input control process of reading encoded data from the recording medium 100 and writing the encoded data to the ring buffer memory 20 (FIG. 3).
And a data output control process (FIG. 4) for reading encoded data required for decoding from the ring buffer memory 20.

In the data input control process, as shown in FIG. 3, first, in step S1-1, it is determined whether or not there is a free area in the ring buffer memory 20. If there is no free space, it will wait until a free space is created,
On the other hand, if there is a free area, the process proceeds to step S1-2.

In step S1-2, the coded data located ahead of the coded data in the ring buffer memory 20 is read from the recording medium 100 as much as there is space in the ring buffer memory 20, and the coded data is read from the ring buffer memory 20. Write to 20 free areas. Thereafter, the process returns to step S1-1 to repeat the processing.

By performing such a data input control process, every time a free 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. It will be.

On the other hand, in the data output control processing, as shown in FIG. 4, first, in step S2-1, it is determined whether or not a request has been received to instruct to read and output encoded data from the ring buffer memory 20. I do. If the output request for the encoded data has not been received, the process waits until the output request for the encoded data comes. On the other hand, if the output request for the encoded data has come, the process proceeds to step S2-2. .

In step S2-2, it is determined whether or not the encoded data requested to be output has already been fetched into the ring buffer memory 20. If the acquisition of the encoded data for which the output request has been made is not completed, the process returns to step S2-1 and repeats the processing until the acquisition of the encoded data is performed by the data input control process. On the other hand, if the acquisition of the encoded data for which the output request has been made has been completed, the process proceeds to step S2-3.

In step S2-3, the coded data requested to be output is output from the ring buffer memory 20. The coded data output from the ring buffer memory 20 is sent to the demultiplexer 5 as described above, and then subjected to decoding processing by each decoder.

Next, in step S2-4, of the storage area of the ring buffer memory 20, the area in which the encoded data that has become unnecessary after the reproduction is completed is written as a free area. Thereafter, the process returns to step S2-1 to repeat the processing. In addition, by the process in step S2-4,
When a free space is generated in the ring buffer memory 20, new encoded data is read from the recording medium 100 by the above-described data input control process, and the encoded data is newly written in the ring buffer memory 20. Become.

FIG. 5 shows a specific example of how the storage area of the ring buffer memory 20 is used when the above-described ring buffer memory control processing is performed. Here, for the sake of convenience, attention is paid only to video data recorded in GOP units, and description of the processing of other data (such as navigation data) is omitted.

First, as shown in FIG. 5A, the recording medium has the ( _n−1 ) th GOP (GOP _n−1 ) and the nth GOP.
It is assumed that the OP (GOP _n ) and the ( _{n + 1} ) th GOP (GOP _{n + 1} ) are recorded. At this time, it is assumed that reverse reproduction is started from GOP _{n + 1} .

At this time, first, as shown in FIG. 5 (b), from the end of GOP _{n + 1} to the head, encoded data is read by an amount corresponding to a free area of the ring buffer memory 20, and the read code is read. The encrypted data is written to the ring buffer memory 20. In the example of FIG.
and _{n + 1} of the encoded data, and the second half of the portion of the encoded data of the GOP immediately preceding the GOP n + ₁ (i.e. GOP _n) are read, are written to the ring buffer memory 20.

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 process, as shown in FIG. 5C, the storage area of the ring buffer memory 20 where the encoded data is stored is changed. Release it to make it an empty area.

Next, as shown in FIG. 5D, the continuation of the coded data is read by an amount corresponding to the free area of the ring buffer memory 20, and the coded data is written to the free area of the ring buffer memory 20. In the example of FIG.
A part of the encoded data of OP _n is read and written in the ring buffer memory 20.

Next, encoded data necessary for decoding a screen to be reproduced is read from the ring buffer memory 20 and sent to the demultiplexer 5. As a result, if there is encoded data that is no longer necessary for the subsequent decoding process, as shown in FIG. 5E, the storage area of the ring buffer memory 20 where the encoded data is stored is changed. Release it to make it an empty area.

Next, as shown in FIG. 5 (f), the continuation of the encoded data is read by the amount corresponding to the empty area of the ring buffer memory 20, and the encoded data is written to the empty area of the ring buffer memory 20. In the example of FIG.
The remainder of the encoded data of OP _n and the GO before GOP _n
Part of the coded data of the latter half of P (that is, GOP _n-1 ) is read and written to the ring buffer memory 20.

Then, in the same manner, the coded data is read from the ring buffer memory 20 and the ring buffer memory 2 storing the coded data that has become unnecessary.
The release of the storage area of 0 and the writing of new encoded data to the ring buffer memory 20 that has become a free area are sequentially and repeatedly performed.

Here, the ring buffer memory 20 has
It has a storage capacity of one GOP or more. In other words, the ring buffer memory 20 has a storage capacity equal to or more than the maximum value of the data amount necessary 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 the reverse reproduction using the ring buffer memory 20 as described above, a process of repeatedly reading the same encoded data from the recording medium 100 to decode each screen at the time of the reverse reproduction becomes unnecessary. .

In the case where the reverse reproduction is performed using the ring buffer memory 20 as described above, the arrangement of the encoded data on the recording medium 100 and the arrangement of the encoded data on the ring buffer memory 20 as shown in FIG. The encoded data is written to the ring buffer memory 20 so that the arrangement of the encoded data at the same time becomes the same.

That is, every time a free area is created in the ring buffer memory 20, the encoded data is read from the recording medium 100, and when the encoded data is sequentially written to the ring buffer memory 20, the encoded data is stored in the ring buffer memory 20. 20 are written continuously. Thereby, the storage area of the ring buffer memory 20 can be used very efficiently.

In other words, by using the ring buffer memory 20 in this manner, the amount of coded data to be held in the ring buffer memory 20 can be minimized, and the amount of data required for one-time decoding can be reduced. If the storage capacity is only the maximum value, the necessary conditions for applying the present invention can be satisfied.

As described above, by applying the present invention, the recording medium 1 for decoding each screen at the time of reverse reproduction is used.
Since the process of repeatedly reading the same data from 00 is not required, reverse playback can be performed at high speed. 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 reproducing apparatuses are originally provided with a ring buffer memory, the amount of change of the apparatus when applying the present invention is small. That is, by applying the present invention, it is possible to increase the speed of reverse reproduction while minimizing the increase in cost.

In the above description, an example has been described in which processing is performed in units of a GOP, which is the minimum unit of a screen group structure including at least one intra-frame predictive coded screen.
It goes without saying that the processing may be performed in units larger than the OP. That is, for example, if the storage capacity of the ring buffer memory 20 is set to 1 VOBU or more,
The processing may be performed in units of OBU, or further, for example, the storage capacity of the ring buffer memory 20 may be set to one cell or more, and the processing may be performed in units of Cell.

In the above description, an example has been given in which the ring buffer memory 20 is used as a storage unit for holding the encoded data read from the recording medium 100. 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 unit for holding the encoded data read from the recording medium. However, if there is a sufficient storage capacity, it goes without saying that the storage means for holding the encoded data read from the recording medium may not be a ring buffer memory.

[0072]

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 system or the like at a higher speed.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a DVD playback device to which the present invention has been applied.

FIG. 2 is a diagram showing a data structure of a DVD format.

FIG. 3 is a diagram showing a flow of a data input control process.

FIG. 4 is a diagram showing a flow of a data output control process.

FIG. 5 is a diagram showing a specific example of how a storage area of a ring buffer memory is used.

[Explanation of symbols]

1 DVD playback device, 2, pickup, 3R
F circuit, 4 data decoder, 5 demultiplexer, 6 video decoder, 7 sub-video decoder,
8 audio decoder, 9 NTSC conversion circuit,
10 D / A conversion circuit, 11 controller, 12
User interface, 13 memories, 15
Frame buffer memory, 20 ring buffer memory, 100 recording medium, 200 monitor

Continued on the front page F term (reference) 5C053 FA06 FA24 GB06 GB08 GB11 GB12 GB21 GB30 GB37 HA25 KA01 KA03 KA24 5C059 KK08 LA01 MA00 MA04 MA05 PP05 PP06 PP14 RB01 RC32 RC34 SS13 SS18 SS30 UA05 UA31 UA36

Claims (6)

[Claims] 1. Encoded data obtained by compressing video data over a plurality of frames using correlation in the time axis direction is recorded in units of a screen group structure including at least one intra-frame predictive encoded screen. Reading means for reading the encoded data from the recording medium; storage means having a storage capacity equal to or larger than the encoded data of one screen group structure and holding the encoded data read from the recording medium by the reading means When reproducing the encoded data recorded on the recording medium in the reverse direction with respect 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 coded data is held in the storage means, and the coded data already read out by the reading means and held in the storage means is decoded for reverse reproduction. If necessary, the reproduction apparatus characterized by performing reading and decoding the coded data stored in the storage means. 2. When performing the reverse reproduction, the storage means stores the unnecessary encoded data when the stored encoded data becomes unnecessary due to the completion of the decoding process. The readout means reads out the next required encoded data if there is a free area in the storage means, and stores the encoded data in the free area of the storage means. 2. The reproducing apparatus according to claim 1, wherein the information is sequentially stored. 3. The reproducing apparatus according to claim 2, wherein said storage means is a ring buffer memory. 4. Encoded data obtained by compressing video data over a plurality of frames using correlation in the time axis direction is recorded in units of a screen group structure including at least one intra-frame predictive encoded screen. When the encoded data is read from the recording medium and 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 and the encoded data is read into one screen. If the encoded data already stored in the storage means is stored in the storage means having a storage capacity equal to or larger than the encoded data of the group structure and is necessary for decoding processing for reverse reproduction. A method for reading encoded data stored in a storage means and decoding the encoded data. 5. When performing the reverse reproduction, if the encoded data held by the storage means becomes unnecessary due to the completion of the decoding process, the unnecessary encoded data is held. If the storage means has a free area, the next necessary coded data is read out, and the coded data is sequentially stored in the free area of the storage means. 5. The reproducing method according to claim 4, wherein the reproducing method is performed. 6. The reproducing method according to claim 5, wherein a ring buffer memory is used as said storage means.