JP4286259B2 - Video playback device and reverse playback method - Google Patents

Description

  The present invention relates to a reverse playback method of digital video data recorded on a recording medium and a video playback device capable of implementing this method.

  As a method for recording / reproducing digital data recorded on a recording medium such as a hard disk or an optical disk, there is a method of handling digital video data compressed and encoded by a Motion Picture Experts Group (MPEG) method in GOP (Group of Picture) units. In this case, complicated data processing is required for special reproduction. The GOP usually includes video information of 15 frames, and the video data of each frame is any one of an I (intra-screen coding) picture, a P (forward prediction coding) picture, and a B (bidirectional prediction coding) picture. Consists of.

  The difficulty in backward reproduction of video data compressed and recorded by the MPEG method is due to predictive coding. In particular, since a B picture is generated by predictive coding with reference to two frames (I picture or P picture) before and after itself in terms of time, complicated processing is required for backward reproduction. I need it. Therefore, a method for realizing reverse frame advance or slow playback by displaying all of the I picture, P picture, and B picture in a digital video playback apparatus adopting the MPEG system has been proposed (for example, see Patent Document 1). ).

Japanese Patent No. 3593293

  However, according to the slow reproduction method of Patent Document 1, in order to obtain an I picture, a P picture, and a B picture to be displayed, it is necessary to repeatedly read the same GOP and decode the same I picture or P picture a plurality of times. Yes, the data processing amount becomes very large. For this reason, this slow playback method can be applied to reverse frame-by-frame playback and reverse playback at a very low speed. There is a problem that it cannot be applied to direction reproduction. The reason for this will be specifically described with reference to FIG.

  In reverse reproduction, after displaying the first picture of the mth GOP (m is a positive integer), that is, the I picture I2 (not shown in FIG. 13), the next display is shown in FIG. The last picture of the (m−1) th GOP shown in FIG. When decoding the P picture P14, it is necessary to sequentially decode from the first picture of the (m-1) th GOP and arrive at the last picture P14 of the (m-1) th GOP. Decoding time for frames is required. Thus, when performing slow reverse playback, {1 / (number of frames constituting one GOP)} double speed, that is, 1 / (in order to perform smooth video display at temporally adjacent GOP boundaries) The upper limit is 15 times normal speed (when 1 GOP is 15 frames), and reverse slow playback at a speed exceeding 1/15 times normal speed cannot be performed with a smooth video.

  Therefore, the present invention has been made to solve the above-described problems of the prior art, and its purpose is to perform smooth reverse video playback at a relatively high speed even at temporally adjacent GOP boundaries. It is an object of the present invention to provide a backward reproduction method realized in the above and a video reproduction apparatus that can implement this method.

The video reproduction apparatus of the present invention includes a reading unit that reads encoded digital video data recorded on a recording medium in units of GOPs, a GOP buffer that temporarily holds the read GOP, and the GOP buffer. A decoder that decodes the held GOP to generate an I picture, a plurality of P pictures, and a plurality of B pictures, a display buffer that outputs a display video signal based on the held pictures, and the digital video data A reference buffer that temporarily holds a plurality of pictures of the generated I picture and a plurality of P pictures, and a reverse reproduction of the digital video data, A process of writing an I picture or a P picture held in the reference buffer to the display buffer, and holding in the reference buffer Has been that I-pictures and P-pictures, or, and a system controller that executes a process of writing with reference to P picture to produce a B-picture in the decoder, said generated B-picture in the display buffer When the digital video data is reproduced in the reverse direction, the system control unit performs a process of writing a picture in the display buffer, an I picture held in the reference buffer, and a P held in the reference buffer. The picture or the generated B picture is executed by overwriting the display buffer one picture at a time in order from the newest picture to the oldest picture, and the I picture or P picture held in the reference buffer At the timing when the process of writing to the display buffer is executed. The I buffer or the P picture newly decoded by the decoder is stored in the reference buffer in which the P picture written in the display buffer at the time point closest to the timing is held. It is characterized by executing an overwriting process .

The backward reproduction method of the present invention also includes a step of reading encoded digital video data recorded on a recording medium in units of GOPs and holding them in a GOP buffer, and decoding the GOP held in the GOP buffer. Generating an I picture and a plurality of P pictures, holding a plurality of pictures of the generated I picture and a plurality of P pictures in a reference buffer, and an I picture held in the reference buffer Alternatively, a process of writing a P picture to a display buffer , or a B picture is generated by referring to an I picture and a P picture stored in the reference buffer , or a P picture, and the generated B picture is displayed. Display video signal based on the picture held in the display buffer by writing to the display buffer A process of writing a picture to the display buffer, and an I picture held in the reference buffer, a P picture held in the reference buffer, or the generated B picture The timing at which execution is performed by overwriting the display buffer one picture at a time in order from the new picture to the old picture, and writing the I picture or P picture held in the reference buffer to the display buffer Thus, the newly decoded I picture or P is stored in the reference buffer in which the P picture written in the display buffer at a time point before the timing and closest to the timing is held. It is characterized by executing a process of overwriting a picture .

  In the present invention, a reference buffer for previously decoding and holding an I picture and / or a P picture in a GOP held in the GOP buffer is provided, and a B picture is referenced with reference to the held I picture or P picture. Decrypt. For this reason, the amount of data processing required to decode a B picture is the amount of data processing for one picture, and every time a GOP held in a GOP buffer is decoded to generate a B picture, the target The amount of data processing can be reduced compared to the conventional case of decoding up to a picture to be performed. Therefore, according to the present invention, there is an effect that it is possible to realize a relatively fast reproduction speed during backward reproduction.

  FIG. 1 is a block diagram schematically showing a configuration of a video playback device 11 (that is, a device capable of performing the backward playback method according to the embodiment) according to the embodiment of the present invention. As shown in FIG. 1, a video reproduction apparatus 11 includes a tuner 2 to which a broadcast signal from an antenna 1 that receives broadcast radio waves is input, a demodulator 3, a switching unit 4, a demultiplexer 5, and a decoder. 6, a recording / reproducing unit (for example, a hard disk drive or an optical disc recording / reproducing unit) 7 for recording or reproducing a digital signal on a built-in or detachable recording medium (eg, hard disk or optical disc) 7a, and recording / reproducing control Unit 8, a memory 9, and a system control unit 10 that controls the entire video reproduction apparatus 11. 1 is a tuner built-in video recording / reproducing apparatus, the present invention can be applied to an apparatus that does not include the tuner 2. 1 has a function of recording a digital signal on the recording medium 7a, the present invention is also applicable to a playback-only apparatus that does not have a function of recording a digital signal. it can. Further, in FIG. 1, the memory 9 is illustrated as a part of the system control unit 10, but the memory 9 may be provided outside the system control unit 10. Furthermore, in FIG. 1, the memory 9 is depicted as a single memory, but the memory 9 may be composed of a plurality of memories.

  The tuner 2 selectively extracts a target carrier wave from the broadcast signal from the antenna 1. The demodulator 3 demodulates the modulated broadcast signal from the tuner 2 to generate a digital multiplexed signal. The digital multiple signal format is, for example, a format that conforms to a transport stream (TS: Transport Stream) defined in MPEG2-Systems (ISO / IEC13818-1) used in digital broadcasting. The switching unit 4 selects either the digital multiplexed signal output from the demodulating unit 3 or the digital multiplexed signal read from the recording / reproducing unit 7 and outputs the selected signal to the demultiplexing unit 5. The demultiplexing unit 5 separates the video and audio signals from the digital multiplexed signal output from the switching unit 4. The decoder 6 decodes (decodes) the signal demultiplexed by the demultiplexing unit 5. The recording / reproducing unit 7 records and stores the received broadcast program in the recording medium 7a, and reproduces the broadcast program recorded in the recording medium 7a. The recording / reproducing control unit 8 controls the recording operation and the reproducing operation of the recording / reproducing unit 7. The memory 9 temporarily stores the working data of the decoder 6 and the digital data read from the recording / reproducing unit 7.

  The system control unit 10 gives instructions to the tuner 2, demodulation unit 3, switching unit 4, decoder 6, recording / playback control unit 8, and memory 9 to control the entire video playback device 11. When recording a broadcast program, the system control unit 10 controls the tuner 2 and the demodulation unit 3 to extract a digital multiple signal of this program. The digital multiplexed signal output from the demodulator 3 is transmitted to the recording / reproducing unit 7 by the switching unit 4.

  FIG. 2 is a diagram for explaining the function of the switching unit 4 shown in FIG. When recording a broadcast program, the switching unit 4 connects the terminals 4 a and 4 c and transmits the digital multiplexed signal from the demodulating unit 3 to the demultiplexing unit 5 and the recording / reproducing unit 7. At this time, when the broadcast program is not viewed in real time by reservation recording or the like, only the path to the recording / reproducing unit 7 is valid, and the transmission to the demultiplexing unit 5 may be invalidated. When the recording / reproducing unit 7 reproduces the broadcast program recorded on the recording medium 7 a, the switching unit 4 connects the terminals 4 b and 4 c and transmits the digital multiplexed signal from the recording / reproducing unit 7 to the demultiplexing unit 5. . At the time of reproduction, the path to the recording / reproducing unit 7 is invalidated.

  When recording a broadcast program, the recording / playback control unit 8 records a time stamp for each TS packet on the recording medium 7a. During normal playback, the recording / playback control unit 8 controls the recording / playback unit 7 to read the TS from the recording medium 7a, refer to the time stamp, and send the TS from the recording / playback unit 7 to the switching unit 4. Do. By referring to the time stamp, the TS can be transmitted at the same timing as the TS arrives. When the recorded program is reproduced, the TS sent from the recording / reproducing unit 7 is input to the demultiplexing unit 5 and separated into video data and audio data. Since the separated video data and audio data are encoded, these data are decoded by the decoder 6. The decoded video data is video-output as an analog signal or a digital signal.

  Next, a method of playing back a program recorded on the recording medium 7a in the slow reverse direction will be described. FIGS. 3A and 3B are diagrams showing timings when reading and sending out the TS recorded on the recording medium 7a. As shown in FIG. 3A, in normal reproduction, TSs are read from the recording medium 7a in the order according to the time stamp and sent out. That is, TSs are read from the recording medium 7a and transmitted in order from the oldest GOP (in the order of GOP-1, GOP-2, GOP-3, and GOP-4). Also, as shown in FIG. 3B, in reverse slow playback, TS is sent in GOP units. The GOP has header information indicating the start of the GOP. The recording / reproducing control unit 8 uses the GOP header information as a reference to record and reproduce the TS in GOP units in order from the temporally new GOP (in the order of GOP-4, GOP-3, and GOP-2). 7 is controlled. Reading from the recording / playback unit 7 is performed in units depending on the file system, and the GOP detection and GOP unit TS transmission are performed by the recording / playback control unit 8.

  4A to 4C are diagrams illustrating a general configuration of a GOP. In decoding the GOP, a P picture is reproduced based on the I picture, and a B picture is reproduced based on the I picture and the P picture or based on the P picture. In the MPEG system, the sequence of encoded pictures shown in FIG. 4A is different from the sequence of pictures reproduced by decoding shown in FIG. 4B. In reverse slow playback, the decoded picture data for GOP shown in FIG. 4B is displayed in reverse order as shown in FIG. 4C. As already described, according to the method described in Patent Document 1, data for GOP is decoded for a total of 15 pictures, and P picture P14 to B picture B0 are displayed in order. The upper limit of the reverse slow playback speed is 1/15 times speed.

  In the reverse slow playback method in the video playback device 11 of the present embodiment, the following control is performed, so that the reverse slow playback is smooth at a relatively fast playback speed (for example, 1/2 times speed). Realize reverse slow-motion video playback. Note that the GOP used in this embodiment is a closed GOP that is independent in GOP units and can be decoded without referring to adjacent GOPs.

  FIG. 5 is a diagram conceptually showing the reference buffers RB1 to RB4 and the display buffer DB0 provided in the memory 9. The reference buffers RB1 to RB4 and the display buffer DB0 are configured to be accessible from the decoder 6. The reference buffers RB1 to RB4 are predetermined areas in the memory 9 that temporarily hold the I picture or P picture decoded by the decoder 6 in order to decode the P picture or B picture. The display buffer DB0 is a predetermined area in the memory 9 that stores the decoded I picture, P picture, or B picture. Each picture stored in the display buffer DB0 is a video that can be viewed by the viewer. Is output. Therefore, if each picture is written (overwritten) in the display buffer DB0, a video signal based on the written picture is output, and a video can be displayed on a display device (not shown).

  FIG. 6A is a diagram showing a decoding process of the first I picture I2 and P pictures P5, P8, P11, and P14 of a GOP composed of 15 pictures, and FIG. 6B shows the decoded I picture. The I2 and P pictures P5, P8, and P11 are held in the reference buffers RB1 to RB4. Next, the P picture P14 is decoded and overwritten on the reference buffer RB1, and the decoded P picture P14 is written in the display buffer DB0 ( Process). In 1 / 2-speed reverse slow playback, control is performed so that the display buffer DB0 is rewritten every 1/15 seconds (time for two pictures during normal playback).

  The flow of the decoding process until the P picture P14 is displayed will be described in detail with reference to FIGS. 6 (A) and 6 (B). Note that each white arrow in FIG. 6B means a decoding process for one picture. As shown in FIG. 6B, first, the I picture I2 is decoded and fetched into the reference buffer RB1, and then the P picture P5 is based on the I picture I2 held in the reference buffer RB1. Decoded and fetched into reference buffer RB2, then P picture P8 is decoded and fetched into reference buffer RB3 based on P picture P5 held in reference buffer RB2, and then held in reference buffer RB3 The P picture P11 is decoded on the basis of the P picture P8, and is taken into the reference buffer RB4. Next, the P picture P14 is decoded based on the P picture P11 held in the reference buffer RB4 and is taken into the reference buffer RB1. At this time, the I picture I2 held in the reference buffer RB1 is overwritten by the P picture P14 and disappears from the reference buffer RB1. The P picture P14 held in the reference buffer RB1 is copied and displayed in the display buffer DB0 for display. The movement of the picture data between the buffers RB1 to RB4 and DB0 is a movement in the memory 9, and the processing time required for the movement of the data is so short that it can be ignored as compared with the decoding process. As shown in FIG. 6B, when displaying the P picture P14, the reference buffer RB1 has the P picture P14, the reference buffer RB2 has the P picture P5, and the reference buffer RB3 has the P picture P8. The reference buffer RB4 holds a P picture P11.

  FIG. 7 is a diagram showing the time required for the decoding process in the present embodiment. As shown in FIG. 7, from the time when the first I picture I2 is decoded to the time when the P picture P14 is displayed, the decoding time for 5 pictures in terms of normal playback (the decoding process for 5 pictures is This corresponds to the decoding process indicated by the five white arrows in FIG. In addition, the processing time required to display each subsequent picture after the P picture P14 is displayed is a decoding time for one picture.

  FIG. 8 is a diagram showing the state of the reference buffers RB1 to RB4, the state of the display buffer DB0, and the picture (white arrow) to be decoded when reverse playback is performed. In FIG. 8, the GOP to be processed is denoted as GOP-a, and the GOP to be processed next to this GOP-a is denoted as GOP-b. These GOPs are sequentially read from the recording medium 7a by the recording / reproducing unit 7. In reading the GOP, as shown in FIG. 9, a storage area capable of storing data for two GOPs, that is, a first GOP buffer 20 and a second GOP buffer 21 are prepared in the memory 9, and GOP-a When the display is completed, the system control unit 10 performs control so that the next GOP, GOP-c, is read from the storage device 7.

  First, as shown in FIG. 9, the processing is started from the state where GOP-a is read from the recording / playback unit 7 to the first GOP buffer 20 and GOP-b is read to the second GOP buffer 21. . 8 and 9, the GOP-a I picture is represented as In-a, the P picture is represented as Pn-a, the B picture is represented as Bn-a, the GOP-b I picture is represented as In-b, and the P picture is represented as Pn. -B, B picture is expressed as Bn-b. In FIG. 9, the I picture of GOP-c is represented as In-c, the P picture as Pn-c, and the B picture as Bn-c. Here, n is an arbitrary number (in this embodiment, n = 0, 1,..., 14). Further, the state S1-a indicates a state where the display of the P picture P14-a is completed.

  Next, as shown in FIG. 8, a P picture P14-a held in the reference buffer RB1 for displaying a B picture B13-a and a P picture P11-a held in the reference buffer RB4 are displayed. The B picture B13-a is decoded by using it and taken into the display buffer DB0 (state S2-a). Next, in order to display the B picture B12-a, similarly to the B picture B13-a, the P picture P14-a held in the reference buffer RB1 and the P picture P11- held in the reference buffer RB4 are displayed. The B picture B12-a is decoded using a and taken into the display buffer DB0 (state S3-a). Each decoding process of the B picture B13-a and the B picture B12-a is a load for one picture as in the normal reproduction, and requires a decoding time for one picture in the normal reproduction.

  Next, the P picture P11-a held in the reference buffer RB4 is copied to the display buffer DB0 to display the P picture P11-a (state S4-a). At the timing of displaying the P picture P11-a, the I picture I2-a in the GOP-a is decoded again and taken into the reference buffer RB1 (state S5-a). At this time, the P picture P14-a disappears from the reference buffer RB1 by overwriting the I picture I2-a. The total load of the display of the P picture P11-a and the decoding process of the I picture I2-a is a load for one picture, and a decoding time for one picture during normal reproduction is required.

  Next, in order to display the B picture B10-a, the B picture B10-a is displayed using the P picture P11-a held in the reference buffer RB4 and the P picture P8-a held in the reference buffer RB3. The data is decoded and taken into the display buffer DB0 (state S6-a). Next, in order to display the B picture B9-a, the B picture B9-a is displayed using the P picture P11-a held in the reference buffer RB4 and the P picture P8-a held in the reference buffer RB3. Decrypt and fetch into the display buffer DB0 (state S7-a).

  Next, the P picture P8-a held in the reference buffer RB3 is copied to the display buffer DB0 to display the P picture P8-a (state S8-a). At the timing of displaying the P picture P8-a, the I picture I2-b in the next GOP (that is, GOP-b) held in the GOP buffer (buffer 21 in FIG. 9) is decoded and taken into the reference buffer RB4. (State S9-a). At this time, the P picture P11-a held in the reference buffer RB4 is overwritten and disappears from the reference buffer. The total load of the display of the P picture P8-a and the decoding process of the I picture I2-b is a load for one picture, and a decoding time for one picture during normal reproduction is required.

  Next, in order to display the B picture B7-a, the P picture P8-a held in the reference buffer RB3 and the P picture P5-a held in the reference buffer RB2 are used to display the B picture B7-a. Is decoded and taken into the display buffer DB0 (state S10-a). Next, in order to display the B picture B6-a, the B picture B6-a is used by using the P picture P8-a held in the reference buffer RB3 and the P picture P5-a held in the reference buffer RB2. Is decoded and taken into the display buffer DB0 (state S11-a).

  Next, the P picture P5-a held in the reference buffer RB2 is copied to the display buffer DB0 to display the P picture P5-a (state S12-a). At the timing of displaying the P picture P5-a, the P picture P5-b in the next GOP (that is, GOP-b) held in the GOP buffer (buffer 21 in FIG. 9) is decoded and taken into the reference buffer RB3. (State S13-a). At this time, the P picture P8-a held in the reference buffer RB3 is overwritten and disappears from the reference buffer.

  Next, in order to display the B picture B4-a, the B picture B4-a is used by using the I picture I2-a held in the reference buffer RB1 and the P picture P5-a held in the reference buffer RB2. Is decoded and taken into the display buffer DB0 (state S14-a). Next, in order to display B picture B3-a, B picture B3-a is used by using I picture I2-a held in reference buffer RB1 and P picture P5-a held in reference buffer RB2. Is decoded and taken into the display buffer DB0 (state S15-a).

  Next, the I picture I2-a held in the reference buffer RB1 is copied to the display buffer DB0, and the I picture I2-a is displayed (state S16-a). At the timing of displaying the I picture I2-a, the P picture P8-b in the next GOP (that is, GOP-b) held in the GOP buffer (buffer 21 in FIG. 9) is decoded and taken into the reference buffer RB2. (State S17-a). At this time, the P picture P5-a held in the reference buffer RB2 is overwritten and disappears from the reference buffer.

  Next, using the I picture I2-a held in the reference buffer RB1, the B picture B1-a is decoded and taken into the display buffer DB0 (state S18-a). Next, using the I picture I2-a held in the reference buffer RB1, the B picture B0-a is decoded and fetched into the display buffer DB0 (state S19-a).

  Next, using the P picture P8-b held in the reference buffer RB2, the P picture P11-b held in the GOP-b is decoded and fetched into the reference buffer RB1 (state S20-a). Thus, the decoding display of each picture in GOP-a is completed, and at the same time, display start preparation for GOP-b, which is the GOP to be displayed next to GOP-a, is completed. Since the display of GOP-a is completed, GOP-c is read out to the first GOP buffer 20 held on the memory 9 here.

  FIG. 10 is a diagram illustrating the state of the reference buffers RB1 to RB4, the state of the display buffer DB0, and the picture (white arrow) to be decoded when reverse playback is performed. FIG. 10 shows processing following the processing shown in FIG. The process of FIG. 10 is started from a state where GOP-c is read into the first GOP buffer 20 and GOP-b is read into the second GOP buffer 21.

  As shown in FIG. 10, since the P picture P11-b in GOP-b is prepared in the state S20-a, the P picture P14-b to be reproduced can be decoded. Therefore, first, using the P picture P11-b held in the reference buffer RB1, the P picture P14-b is decoded and taken into the reference buffer RB4 (state S1-b). Then, the P picture P14-b is written into the display buffer DB0, and the P picture P14-b is displayed.

  Next, in order to display the B picture B13-b, the B picture B13-b is used by using the P picture P14-b held in the reference buffer RB4 and the P picture P11-b held in the reference buffer RB1. Decode and fetch into display buffer DB0 (state S2-b).

  Next, in order to display the B picture B12-b, similarly to the B picture B13-b, the P picture P14-b held in the reference buffer RB4 and the P picture P11-b held in the reference buffer RB1 are displayed. Is used to decode the B picture B12-b and fetch it into the display buffer DB0 (state S3-b).

Next, the P picture P11-b held in the reference buffer RB1 is copied to the display buffer DB0 to display the P picture P11-b (state S4-b).
At the timing of displaying the P picture P11-b, the I picture I2-b in the GOP-b is decoded again and taken into the reference buffer RB4 (state S5-b). At this time, the P picture P14-b disappears from the reference buffer RB4 due to overwriting of the I picture I2-a.

  Next, in order to display the B picture B10-a, the B picture B10-b is displayed using the P picture P11-b held in the reference buffer RB1 and the P picture P8-b held in the reference buffer RB2. Decode and fetch into display buffer DB0 (state S6-b). Next, in order to display the B picture B9-b, the B picture B9-b is displayed using the P picture P11-a held in the reference buffer RB1 and the P picture P8-b held in the reference buffer RB2. Decrypt and fetch into the display buffer DB0 (state S7-b).

  Next, the P picture P8-b held in the reference buffer RB2 is copied to the display buffer DB0 and displayed (state S8-b). At the timing of displaying the P picture P8-b, the I picture I2-c in the next GOP (that is, GOP-c) held in the GOP buffer (buffer 20 in FIG. 9) is decoded and taken into the reference buffer RB1. (State S9-b). At this time, the P picture P11-b held in the reference buffer RB1 is overwritten and disappears from the reference buffer.

  Next, in order to display the B picture B7-b, the P picture P8-b held in the reference buffer RB2 and the P picture P5-b held in the reference buffer RB3 are used to display the B picture B7-b. Is decoded and taken into the display buffer DB0 (state S10-b). Next, in order to display the B picture B6-b, the B picture B6-b is used by using the P picture P8-b held in the reference buffer RB2 and the P picture P5-b held in the reference buffer RB3. Is decoded and taken into the display buffer DB0 (state S11-b).

  Next, the P picture P5-b held in the reference buffer RB3 is copied to the display buffer DB0, and the P picture P5-b is displayed (state S12-b). At the timing of displaying the P picture P5-b, the P picture P5-c in the next GOP (that is, GOP-c) held in the GOP buffer (buffer 20 in FIG. 9) is decoded and taken into the reference buffer RB2. (State S13-b). At this time, the P picture P8-b held in the reference buffer RB2 is overwritten and disappears from the reference buffer.

  Next, in order to display the B picture B4-b, the B picture B4-b is used by using the I picture I2-b held in the reference buffer RB4 and the P picture P5-b held in the reference buffer RB3. Is decoded and taken into the display buffer DB0 (state S14-b). Next, in order to display the B picture B3-b, the B picture B3-b is used by using the I picture I2-a held in the reference buffer RB4 and the P picture P5-b held in the reference buffer RB3. Is decoded and taken into the display buffer DB0 (state S15-b).

  Next, the I picture I2-b held in the reference buffer RB4 is copied to the display buffer DB0, and the I picture I2-b is displayed (state S16-b). At the timing of displaying the I picture I2-b, the P picture P8-c in the next GOP (that is, GOP-c) held in the GOP buffer (buffer 20 in FIG. 9) is decoded and taken into the reference buffer RB3. (State S17-b). At this time, the P picture P5-b held in the reference buffer RB3 is overwritten and disappears from the reference buffer.

  Next, using the I picture I2-b held in the reference buffer RB4, the B picture B1-b is decoded and taken into the display buffer DB0 (state S18-b). Next, using the I picture I2-b held in the reference buffer RB4, the B picture B0-b is decoded and taken into the display buffer DB0 (state S19-b).

  Next, using the P picture P8-c held in the reference buffer RB3, the P picture P11-c held in the GOP-c is decoded and fetched into the reference buffer RB4 (state S20-b). Up to this point, the decoding and display of each picture in GOP-b is completed, and the display start preparation for GOP-c, which is the next GOP, is completed. After that, reproduction control is performed by repeating the above-described series of flows.

  FIG. 11 is a diagram illustrating a relationship between a picture to be decoded, a picture to be displayed, and the number of processes required for decoding (decode number) in the data processing illustrated in FIG. Generation of a B picture is performed by performing decoding processing with reference to data in two reference buffers out of four reference buffers, and display of the B picture is performed by copying the generated B picture to the display buffer DB0. Is done by. As for the P picture and the I picture, those previously decoded and prepared in the reference buffers RB1 to RB4 are copied and displayed in the display buffer DB0 when necessary. For example, when displaying the P picture P11-a, since it is already held in the reference buffer RB4, the I picture I2 of the next GOP-b is decoded and prepared here. Further, when displaying the P picture P8, since it is already held in the reference buffer RB3, the P picture P5 of the next GOP is decoded and prepared here. Here, for example, between the B picture B0 and the P picture P14 at the boundary of the GOP, it is necessary to decode the B picture B0-a and the P picture P11-b, for example. In FIG. 11, the number of decoding processes is expressed as “2” in that sense. By controlling in this way, it is sufficient to decode at most two pictures in a period during which one frame of video is displayed. In reverse slow playback, the display time for one frame (one picture) is 1/15 second at 1/2 times speed, and at this time, decoding processing for up to two pictures and memory copy if necessary It's a good thing to do. This is a level that can be processed if there is processing capability equivalent to that during normal playback.

  FIG. 12 is a diagram illustrating a relationship between a picture to be decoded, a picture to be displayed, and the number of processes required for decoding (decode number) in the data processing illustrated in FIG. For the same reason as in the case of FIG. 11, in the reverse slow playback, if the speed is ½ times, the display time for one frame (one picture) is 1/15 seconds, and at this time, a maximum of two pictures are displayed. Decoding processing and memory copying may be performed if necessary. This is a level that can be processed if there is processing capability equivalent to that during normal playback.

  As described above, in the present embodiment, the encoded digital video data recorded on the recording medium 7a is read in GOP units and held in the GOP buffer 20 or 21, and the GOP buffer 20 or 21 Decoding the GOP held in step S1 to generate an I picture and a plurality of P pictures, and holding a plurality of pictures of the generated I picture and the plurality of P pictures in the reference buffers RB1 to RB4 The process of writing the I picture or P picture held in the reference buffers RB1 to RB4 to the display buffer DB0, or the B picture by referring to the I picture or P picture held in the reference buffers RB1 to RB4 Displayed by processing to generate and write the generated B picture to the display buffer DB0 A step of outputting a display video signal based on a picture held in the buffer DB0, and a process of writing a picture in the display buffer DB0 is performed by an I picture and a reference buffer RB1 held in the reference buffers RB1 to RB4. The P picture held in RB4 or the generated B picture is overwritten one by one in the display buffer DB0 in order from the newest picture to the oldest picture. As described above, the I pictures held in the reference buffers RB1 to Rb4 are provided by including the reference buffers RB1 to Rb4 for decoding and holding the I picture and the P picture in the GOP held in the GOP buffer 20 or 21 in advance. Alternatively, the B picture can be decoded with reference to the P picture. Therefore, the amount of data processing can be reduced as compared with the conventional reproduction method in which the GOP held in the GOP buffer 20 or 21 is decoded from the beginning every time the B picture is decoded. Therefore, according to the backward reproduction method of the present embodiment, smooth backward reproduction of video can be executed at a relatively high speed.

  In the present embodiment, when all the pictures held in the reference buffers RB1 to RB4 are P pictures, a process of writing the P pictures held in the reference buffers RB1 to RB4 to the display buffer DB0 is performed. At the execution timing (states S4-a and S5-a in FIG. 8), a decoded I picture is generated from the GOP held in the GOP buffer 20 or 21, and the generated I picture is referred to the reference buffers RB1 to RB1. A process of overwriting one of the P pictures held in RB4 (P14-a in FIG. 8) is executed. Since the process of writing the P pictures held in the reference buffers RB1 to RB4 to the display buffer DB0 is a data movement in the memory 9 and a process with a small load, the states S4-a and S5-a in FIG. This process can be realized within one decoding time if there is a decoding processing capability during normal reproduction. Therefore, according to the backward reproduction method of the present embodiment, smooth backward reproduction of video can be executed at a relatively high speed.

  Further, in the present embodiment, the timing at which the process of writing the I picture or P picture held in the reference buffers RB1 to RB4 to the display buffer DB0 is executed (states S4-a, S8-a, S12 in FIG. 8). In -a, S16-a), a new decoding is performed in the reference buffer that holds the P picture written in the display buffer DB0 at a time earlier than this timing and closest to this timing. The process of overwriting the I picture (state S6-a in FIG. 8) or P picture (states S5-a, S9-a, S13-a, S17-a in FIG. 8) is executed. For this reason, the memory utilization efficiency can be improved as compared with a method in which all the pictures constituting the GOP are decoded and held in the buffer.

  In the present embodiment, the GOP (for example, FIG. 5) that is currently the decoding target at the timing of executing the process of writing the I picture or P picture held in the reference buffers RB1 to RB4 to the display buffer DB0. 8 and GOP-a in FIG. 9 and other GOPs that are temporally older (for example, GOP-b in FIGS. 8 and 9) are decoded to generate I or P pictures, and other GOPs (for example, A process of overwriting any picture in the reference buffers RB1 to RB4 with the I picture or P picture generated by decoding GOP-b) in FIGS. 8 and 9 (states S9-a and S13 in FIG. 8). -A, S17-a, S20-a). For this reason, smooth display without unnaturalness is possible at the boundary between GOP-a and GOP-b to be reproduced next.

1 is a block diagram schematically showing a configuration of a video reproduction apparatus according to an embodiment of the present invention. It is a figure for demonstrating the function of the switching part shown by FIG. (A) is a diagram showing TS transmission timing at the time of normal reproduction in which data on a recording medium is read out in order from oldest data in time; (B) is a reverse view of reading out data on a recording medium in order from newest data in time. It is a figure which shows the TS transmission timing at the time of direction slow reproduction | regeneration. (A) is a diagram showing encoded pictures constituting the GOP, (B) is a diagram showing pictures after decoding, and (C) is a display order of pictures during backward reproduction. FIG. It is a figure which shows the reference buffer and display buffer which were prepared on the memory of FIG. (A) And (B) is a figure which shows typically the initial control state of the reference buffer in embodiment of this invention. It is a figure which shows the decoding processing time in embodiment of this invention. It is a figure which shows typically the control state of the reference buffer and display buffer in embodiment of this invention. It is a figure which shows the process which overwrites GOP to the GOP buffer prepared on the memory of FIG. It is a figure which shows typically the control state (state following FIG. 8) of the reference buffer and display buffer in embodiment of this invention. It is a figure which shows the number of decoding processes in FIG. It is a figure which shows the number of decoding processes in FIG. It is a figure which shows typically the slow reproduction method in the conventional video reproduction apparatus.

Explanation of symbols

1 antenna, 2 tuner, 3 demodulating unit, 4 switching unit, 5 demultiplexing unit, 6 decoder, 7 recording / playback unit, 7a recording medium, 8 recording / playback control unit, 9 memory, 10 system control unit, 11 video playback device, 20 first GOP buffer, 21 second GOP buffer, DB0 display buffer, RB1 to RB4 reference buffer.

Claims (8)

A reading unit for reading encoded digital video data recorded on a recording medium in GOP units;
A GOP buffer for temporarily holding the read GOP;
A decoder that decodes the GOP held in the GOP buffer to generate an I picture, a plurality of P pictures, and a plurality of B pictures;
A display buffer for outputting a display video signal based on the held picture;
A reference buffer that temporarily holds a plurality of pictures of the generated I picture and a plurality of P pictures when the digital video data is reproduced in the reverse direction;
A process of writing an I picture or a P picture held in the reference buffer to the display buffer when the digital video data is reproduced in the reverse direction; and an I picture and a P picture held in the reference buffer ; Or a system control unit that executes a process of causing the decoder to generate a B picture with reference to a P picture and writing the generated B picture to the display buffer,
When the digital video data is reproduced in the reverse direction, the system control unit performs a process of writing a picture in the display buffer by executing an I picture held in the reference buffer and a P picture held in the reference buffer. Or by overwriting the generated B picture one by one in the display buffer in order from the newest picture to the oldest picture, and the I picture or the P picture held in the reference buffer The reference buffer in which the P picture written in the display buffer is held at a timing that is earlier than the timing and closest to the timing at the time when the processing for writing into the display buffer is executed The I picture or P picture newly decoded by the decoder Video reproducing apparatus characterized by performing a process of overwriting the.   When all the pictures held in the reference buffer are P pictures when the digital video data is reproduced in the reverse direction, the system control unit displays the P pictures held in the reference buffer as the display One of the P pictures held in the reference buffer is generated by generating a decoded I picture from the GOP held in the GOP buffer at the timing when the process of writing to the buffer is executed The video reproducing apparatus according to claim 1, wherein a process of overwriting is executed. When the digital video data is reproduced in the reverse direction, the system control unit becomes a current decoding target at the timing when the process of writing the I picture or P picture held in the reference buffer to the display buffer is executed. Another GOP that is older than the current GOP is decoded by the decoder to generate an I picture or P picture, and the I picture or P picture generated by decoding the other GOP is stored in any of the reference buffers. video reproducing apparatus according to claim 1 or 2, characterized in that to execute a process of overwriting the Kano picture. GOP held in the GOP buffer is any one of claims 1 to 3, wherein the number of pictures to be held in the reference buffer includes one I-picture and four P-picture is four The video playback device described in 1. Reading the encoded digital video data recorded on the recording medium in units of GOPs and holding them in a GOP buffer;
Decoding the GOP held in the GOP buffer to generate an I picture and a plurality of P pictures, and holding a plurality of pictures of the generated I picture and the plurality of P pictures in a reference buffer When,
A process of writing an I picture or a P picture held in the reference buffer to a display buffer , or generating a B picture by referring to an I picture and a P picture held in the reference buffer , or a P picture Outputting a display video signal based on the picture held in the display buffer by a process of writing the generated B picture to the display buffer;
A process of writing a picture to the display buffer is performed by changing an I picture held in the reference buffer, a P picture held in the reference buffer, or the generated B picture from a new picture in time to an old picture. run by overwriting one picture to the display buffer in the order toward the,
The display buffer at the timing when the process of writing the I picture or the P picture held in the reference buffer to the display buffer is executed, at a time earlier than the timing and closest to the timing A backward reproduction method characterized by executing a process of overwriting a newly decoded I picture or P picture in the reference buffer in which the P picture written in is held . When all the pictures held in the reference buffer are P pictures, the picture is held in the GOP buffer at the timing of executing the process of writing the P picture held in the reference buffer to the display buffer. to generate an I-picture decoded from GOP, as claimed in claim 5, characterized in that executes processing for overwriting an I-picture that is the product to any of the P-picture stored in the reference buffer Reverse playback method. At the timing when the process of writing the I picture or P picture held in the reference buffer to the display buffer is executed, another GOP that is temporally older than the GOP currently being decoded is decoded and the I picture 7. The process according to claim 5 or 6 , wherein a process of generating a P picture and overwriting any picture in the reference buffer with an I picture or a P picture generated by decoding the other GOP is performed. The reverse playback method as described. GOP wherein held in the GOP buffer is any one of claims 5 to 7, characterized in that the number of pictures to be held in the reference buffer includes one I-picture and four P-picture is four The reverse direction reproduction method as described in 2.

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