JP3695424B2 - Playback device - Google Patents

Description

[0001]
[Industrial application fields]
The present invention reads out data from a disc on which time-division multiplexed signals that have been time-division-multiplexed by performing compression processing on moving image data and audio data, and reverse playback and reverse low-speed (slow) playback of images. The present invention relates to a playback apparatus suitable for a case where reverse frame advance playback is performed.
[0002]
[Prior art]
As a method for compressing moving image data and audio data, a conventional MPEG (Motion Picture Coding Experts Group) method has been proposed. By this MPEG method, moving image data and audio data are subjected to compression processing, and a disk is sometimes used. Divided multiplex recording is performed. An example of the data format of the multiplexed data is shown in FIG.
As shown in FIG. 11 (a), one unit of the multiplexed bit stream in the multiplexed data recorded in a time division multiplexed manner on the disc is composed of at least one pack (PACK) and ISO_11172_end_code indicating the end. Is done. This ISO_11172_end_code is a 32-bit code and is defined as “0x000001b9” in hexadecimal. The leading “0x” represents a hexadecimal number (C language).
[0003]
Further, as shown in FIG. 5B, the pack is composed of a header composed of Pack_Start_Code, SCR (System Clock Referece), and MUX_Rate, and at least one packet. The Pack_Start_Code of this header is a 32-bit code and is defined as “0x000001b4” in hexadecimal.
Although the length of the pack is defined as a variable length, it may be fixed to 2048 bytes, for example. In the following description, it is assumed that the length is fixed to 2048 bytes.
[0004]
Further, as shown in FIG. 5C, the packet constituting the pack includes a header composed of Packet_Start_Code_Prefix, Stream_ID, Packet_length, PTS (Presentation Time Stamp), and DTS (Decoding Time Stamp), and packet data (Code Data). It consists of.
This Packet_Start_Code_Prefix is a 24-bit code and is defined as “0x000001” in hexadecimal. Stream_ID is an 8-bit code and indicates the type of packet (Stream Type) as shown in FIG. Further, Packet_length (16 bits) indicates the length of the subsequent packet.
[0005]
In the packet data (Code Data) of each packet, audio data is recorded in the case of an audio stream, and video data is recorded in the case of a video stream. Also, since the audio stream can have 32 types and the video stream can have 16 different stream ids, a plurality of audio signals and video signals up to this number can be multiplexed.
[0006]
FIG. 13 is a block diagram showing a schematic configuration of a conventional encoded data decoding apparatus that reproduces such multiplexed data.
In the encoded data reproduction apparatus shown in this figure, the time division multiplexed data read from the DSM (Digital Storage Media) 10 is supplied to the separation apparatus 21, and the header separation circuit 22 converts the time division multiplexed data from the pack header. The packet header is separated and supplied to the control device 24, and the time-division multiplexed data is supplied to the input terminal G of the switching circuit 23. Output terminals H1 and H2 of the switching circuit 23 are connected to input terminals of a video decoder 25 and an audio decoder 26, respectively.
[0007]
In addition, the control device 24 of the separation device 21 connects the input terminal G of the switching circuit 23 to the output terminal H1 in the case of a video signal in accordance with the stream id of the packet header supplied from the header separation circuit 22 to the video decoder 25. In the case of an audio signal, the input terminal G of the switching circuit 23 is connected to the output terminal H2 and the signal is sent to the audio decoder 26, so that the time-division multiplexed data is correctly separated and handled accordingly. The data is supplied to the decoder.
[0008]
Next, an outline of MPEG will be described. MPEG has an intra-frame encoded picture (I picture), an inter-frame forward predictive encoded picture (P picture), and a bi-directional predictive encoded picture (B picture). ing. The I picture is encoded by using only the data in the image (frame or field). For this reason, the compression efficiency of I picture data is low, but since it is encoded within a frame, it can be decoded only by itself.
[0009]
On the other hand, a P picture is a picture that has undergone predictive coding by calculating a difference from the previous I picture or P picture, and the compression efficiency is increased. However, when decoding, it is necessary that the previous I picture or P picture referenced at the time of predictive encoding is decoded.
A B picture is a picture that has been subjected to predictive coding by calculating a difference from the preceding and following I pictures or P pictures, and has the highest compression efficiency. However, in the case of decoding, it is necessary that the preceding and succeeding I pictures or P pictures referenced at the time of predictive encoding are decoded.
[0010]
Here, FIG. 14 shows a conceptual diagram of a bit stream including an I picture, a P picture, and a B picture recorded in the DSM 10 as a disc.
As shown in this figure, a continuous video bit stream is divided into one or more GOPs (Group of Pictures). This GOP has Group-Start-Code (GSC), Time-Code (TC), Closed GOP (CG), and Broken-Link (BC) data in the header, followed by multiple picture data. ing. Note that the head of picture data in a GOP is defined as an I picture.
[0011]
By the way, when the time-division multiplexed video data is compressed by the MPEG encoding method, the random access and the search operation are limited. That is, when random access is made to a disc recorded in MPEG, pictures prior to the picture accessed at the time of access have not been read, so pictures other than I pictures cannot be decoded. Needs access to the I picture. For this reason, in the normal MPEG system, about two I-pictures appear per second so that the random accessibility and the compression efficiency are balanced.
[0012]
In addition, when video data is compressed at a fixed rate, an I picture periodically appears at a predetermined position, so that the position can be obtained by calculation and accessed. However, when variable-rate compression is performed, the position of the I picture is indefinite, making access difficult.
In the case of MPEG, it is usually a variable rate compression.
[0013]
Therefore, in the encoded data decoding apparatus shown in FIG. 13, when a search command is received so that random access is performed, the following operation is performed.
When receiving the search command, the main control device (not shown) commands the control device 24, the video decoder 25 and the audio decoder 26 to shift to the search mode. In the transitioned search mode, the video decoder 25 selects and decodes only I picture data from the input video data. Alternatively, only I picture data is selected by the separation device 21 and input to the video decoder 25. In the video decoder 25, the input I picture data is decoded and output.
Thereby, the searched image is displayed.
[0014]
In the search mode, the control device 24 instructs the DSM 10 to move a data reading position on the disk forward (or backward). The amount of movement of the reading position at this time depends on the search speed, coding rate, and the like, but generally, the amount of movement increases as the search speed increases and the coding rate increases.
When the reading position moves to a predetermined position, the data output from the DSM 10 is input to the separation device 21, and the header separation circuit 22 separates the video data and supplies it to the video decoder 25. The video decoder 25 decodes and outputs the first I picture that appears. Thereby, the searched image is displayed. In the search mode, the audio decoder 26 is muted.
[0015]
In this way, the search operation in which I pictures are continuously reproduced is realized as repeated random access. That is, for example, when a high-speed forward search is instructed by the user, the video decoder 25 skips reading a predetermined number of frames of input data, searches for an I picture, decodes and outputs it. .
Alternatively, the I picture is searched in the separation device 21, and only the data of the I picture is supplied to the video decoder 25 and decoded. By repeating such an operation, a search operation in which I pictures are continuously reproduced is realized.
[0016]
However, conventionally, since it is not known where the I picture for searching and displaying a desired image is, there is a drawback that it takes a lot of time to access the I picture on which the desired image is displayed.
Therefore, an encoded data decoding apparatus that solves this problem has been proposed. An example of the configuration of the encoded data decoding apparatus is shown in FIG.
[0017]
In the encoded data decoding apparatus shown in this figure, data recorded on the optical disk 60 is reproduced by a pickup 61. The output signal of the pickup 61 is input to the demodulation circuit 62. The demodulation circuit 62 demodulates the reproduction signal output from the pickup 61 and outputs it to the ECC circuit 63. The ECC circuit 63 performs error detection / correction on the input data and outputs the data to the demultiplexer circuit 64.
The video data separated in the demultiplexer circuit 64 is input to the video decoder 65, and the audio data is input to the audio decoder 66, from which a decompressed signal is output.
[0018]
The controller (main control device) 67 sends commands to the video decoder 65 and the audio decoder 66 and controls them according to instructions from the user, and gives an access command to the drive control device 69. Thus, the drive control device 69 accesses the disk 60 by driving the pickup 61 using the tracking servo circuit 70 in accordance with a command from the controller 67.
Further, the TOC data located at the head of the data is separated by the demultiplexer circuit 64, input to the controller 67, and stored in the TOC storage device 68. The TOC data is read from the TOC storage device 68 when necessary, and the controller 67 uses it.
[0019]
Next, the operation of the data decoding apparatus shown in FIG. 15 will be described. When the optical disk 60 is inserted, the controller 67 gives a command for reading the first sector to the drive control apparatus 69. The drive control device 69 drives the pickup 61 by the tracking servo circuit 70 and starts reproduction from the position of the head sector on the disk 60.
The pickup 61 irradiates the optical disc 60 with a laser beam and reproduces data recorded on the optical disc 60 from the reflected light. The reproduction signal output from the pickup 61 is input to the demodulation circuit 62 and demodulated. The demodulated data string is input to the ECC circuit 63, and data error detection / correction is performed. The error-corrected data is input to the demultiplexer circuit 64.
[0020]
Next, in the encoded data decoding apparatus shown in FIG. 15, when receiving a search command to perform random access, the controller 67 sets the search mode to the drive control apparatus 69, the video decoder 65, and the audio decoder 66. Command a transition. In the search mode, the video decoder 66 decodes only I picture data from the input video data. Alternatively, only I picture data is selected by the demultiplexer circuit 64 and input to the video decoder 65. Thereby, in the video decoder 65, the I picture data is decoded and displayed on a display (not shown).
[0021]
In the search mode, the drive control device 69 commands the tracking servo circuit 70 to command to move the data reading position on the disk forward (or backward). The amount of movement of the reading position at this time depends on the search speed, coding rate, and the like, but generally the amount of movement increases as the search speed increases and the coding rate increases.
When the reading position moves to a predetermined position, the data output from the pickup 61 is input to the demultiplexer circuit 64 via the demodulation circuit 62 and the ECC circuit 63. The demultiplexer circuit 64 separates the video data and supplies it to the video decoder 65. The video decoder 65 decodes and outputs the first I picture that appears. In the search mode, the audio decoder 66 is muted.
[0022]
That is, the search operation is realized as repeated random access to the I picture. That is, for example, when a high-speed forward search is instructed by the user, the video decoder 65 skips data of a predetermined number of frames from the input data, searches for an I picture, decodes it, and outputs it. Alternatively, the controller 67 gives a command to the drive control circuit 69 based on the information recorded in the TOC storage device 68, and the drive control circuit 69 drives the tracking servo circuit 70 to search the I picture, and the I picture data Are supplied to the video decoder 65 and decoded. The search operation is performed by repeating such an operation.
[0023]
By the way, the position of the I picture can be stored in the disk 60 as TOC data and used by detecting the information. However, when the position of all the I pictures is to be stored in the disk 60, 1 Assuming that two I pictures are generated per second, the number of I pictures recorded on a recording medium having a capacity of one hour is 7200. It is difficult to store all the positions on the disk 60 as TOC data from the viewpoint of capacity, and the disk 60 can actually record only the position of the first I picture of each track. Therefore, there is a problem that it is practically difficult to perform a precise search operation using the TOC data stored in the disk 60.
In addition, the same problem occurs not only in the disk but also in other storage media.
[0024]
Therefore, a data decoding device described in Japanese Patent Application No. 5-235121 has been proposed in which an entry packet is provided in a bit stream so that a search can be easily performed. As shown in FIG.
FIG. 17 shows an example of the data format in this case. In this data format, the entry packet (Entry Packet) is multiplexed before the video packet including the entry point in the multiplexed data. Has been.
FIG. 18 shows another example of the data format. In this data format, position information of three entry points in the forward direction and the backward direction is recorded in each packet.
[0025]
Next, the operation of the encoded data decoding apparatus shown in FIG. 16 will be described in the case where the data having the format shown in FIG. 17 or 18 is decoded.
The header separation circuit 22 of the separation device 21 separates the pack header, the packet header, and the entry packet from the data read from the DSM 10 and supplies them to the control device 24, and the time division multiplexed data is supplied to the switching circuit 23. Supply to input terminal G. Output terminals H1 and H2 of the switching circuit 23 are connected to input terminals of a video decoder 25 and an audio decoder 26, respectively.
[0026]
Further, the control device 24 reads information on the entry point (information on the entry packet) from the data input from the header separation circuit 22 and supplies the information to the entry point storage device 41 for writing. Since the information on the current reading position is supplied from the DSM 10 to the control device 24, the control device 24 stores the entry point position and its contents in the entry point storage device 41 in association with the current reading position. I can do it.
[0027]
The control device 24 of the separating device 21 is time-division multiplexed by sequentially connecting the input terminal G and the output terminals H1, H2 of the switching circuit 23 according to the stream id in the packet header supplied from the header separating circuit 22. The data is correctly separated, and the video data is supplied to the video decoder 25 and the audio data is supplied to the audio decoder 26, respectively.
[0028]
Next, when a search operation is commanded, the main control device (not shown) commands the control device 24, the video decoder 25, and the audio decoder 26 to shift to the search mode. The control device 24 reads the current read position from the output of the DSM 10 and extracts the entry point near the position from the entry point storage device 41. The entry point storage device 41 stores information on entry packets reproduced in the reproduction mode as needed. Alternatively, all or a predetermined range of entry packets recorded on the disk mounted on the DSM 10 at a predetermined timing, such as when the power of the apparatus is turned on, when a disk is mounted, or when playback is commanded. This information may be read and stored in advance.
[0029]
When the control device 24 obtains the entry point, it sends a search command to the DSM 10 to move the reading position to the entry point at a high speed. When the movement is completed, the DSM 10 reproduces data from the entry point and supplies it to the separation device 21.
When the data format is as shown in FIG. 17, the entry packet is arranged immediately before the video data in which the I picture is recorded. Accordingly, when the video data following the entry packet is separated by the header separation circuit 22 and supplied to the video decoder 25, the first picture of this video data is made an I picture.
Therefore, the video decoder 25 immediately decodes and outputs the first I picture that appears. As a result, the searched image is displayed.
[0030]
Further, when the data format is as shown in FIG. 18, since the position information of the three entry points before and after is recorded in the entry packet, the control device 24 determines the next information from the position information. The entry packet is searched and played back repeatedly. As a result, the I picture is quickly and sequentially decoded, and the searched image is displayed.
[0031]
When the search speed is high, the control device 24 allows access to a farther entry point, and when the search speed is low, the control apparatus 24 accesses a closer entry point. As shown in FIG. 18, when three entry points are recorded in the forward direction and the reverse direction, respectively, there are three or more search speed variations depending on the combination of entry points to be selected. Can do.
As described above, in the encoded data decoding apparatus shown in FIG. 17, the position of the I picture that is the access point can be known from the entry packet, so that the search operation can be completed quickly.
[0032]
In addition, a technique for recording the position (access point) of a nearby I picture as subcode data in the sector header has been proposed, and a similar search operation can be realized using this technique.
[0033]
Further, the MPEG2 System defines a PSD (Program Stream Directory). The structure of this PSD is shown in FIG. 19, but a similar search operation can be realized even when the position of the entry point is recorded by prev_directory_offset, next_directory_offset, and PES_header_position_offset shown in FIG.
[0034]
[Problems to be solved by the invention]
By the way, video equipment such as a VTR is required to have functions such as reverse playback, reverse slow playback, and reverse frame advance playback in addition to normal playback and search operations.
However, the moving image data recorded in accordance with ISO11172-2 (MPEG1 Video) and ISO13818-2 (MPEG2 Video) is referred to as shown in FIG. 20 (a). Therefore, FIG. 20 (b) The order of picture data is recorded in the order shown in FIG.
That is, as shown in FIG. 20A, the structure of inter-frame prediction in the MPEG system is composed of, for example, 15 frames in 1 GOP (Group Of Pictures). In 1 GOP, 1 frame of I picture and 4 frames of P picture The remaining 10 frames are B pictures.
[0035]
The I picture is an intra-frame predictive encoded image that is predictively encoded within one frame, and the P picture is a frame that is already encoded and predicted with reference to a temporally previous frame (I picture or P picture). Since it is an inter-forward prediction encoded image, and a B picture is a bidirectional predictive encoded image that is predicted with reference to two frames preceding and following in time, the I picture I ₂ is the frame as shown by the arrows. P picture P ₅ is inter-frame predictive encoded with reference to I picture I ₂ , and P picture P ₈ is inter-frame predictive encoded with reference to P picture P ₅ . Has been. Further, the B pictures B ₃ and B ₄ are interframe predictively encoded with reference to two of the I picture I ₂ and the P picture P ₅ , and the B pictures B ₆ and B ₇ are P pictures P ₅ and P ₅ , respectively. Inter-frame predictive coding is performed with reference to two pictures P ₈ . Thereafter, the subsequent encoding is performed in the same manner and the subsequent pictures are created.
[0036]
By the way, in order to decode a picture that has been predictively encoded in this way, an I picture is subjected to predictive encoding within a frame, so that it can be decoded only by an I picture, but a P picture is temporally Therefore, the temporally preceding I picture or P picture is required for decoding, and the B picture is temporally preceding or following the I picture or P picture. Therefore, temporally preceding and following I pictures or P pictures are required for decoding.
Therefore, the pictures are replaced as shown in FIG. 20B so that the pictures required for decoding can be decoded first.
[0037]
As shown in the figure, since the B pictures B ₀ and B ₁ require the I picture I ₂ at the time of decoding, the B picture B _{3 is set} so that the I picture I ₂ precedes the B pictures B ₀ and B _1. , B ₄ require I picture I ₂ and P picture P ₅ at the time of decoding, so that B picture B ₆ , B ₇ is also decoded at the same time so that P picture P ₅ precedes B picture B ₃ , B _4. requires a P picture P ₅ and P picture P _8, so that P picture P ₈ the B picture B _6, B ₇ is preceded, B pictures B _9, B ₁₀ is P picture P ₈ and P picture P when decoding ₁₁ is required, so that the P picture P ₁₁ is replaced with the B picture B ₉ , B ₁₀ . Similarly, the B picture B ₁₂ and B ₁₃ are replaced with the P picture P ₁₄ so as to precede it.
[0038]
If such a bit stream is transferred to the video decoder in the order shown in FIG. 20B, normal reproduction can be performed, but there is a problem that other special reproduction cannot be performed as it is. .
Moreover, in the above-described conventional encoded data decoding apparatus, although an implementation method has been disclosed for a search operation for continuously displaying only I pictures, all including not only I pictures but also P pictures and B pictures are disclosed. There is a problem that it is difficult to realize reverse playback, reverse slow playback, and reverse frame-by-frame playback by continuously displaying the frames in reverse order.
[0039]
Therefore, the present invention has been made in view of such a situation, and can perform reverse playback, which can continuously display all frames including not only I pictures but also P pictures and B pictures in reverse order. It is an object of the present invention to provide a playback apparatus that enables reverse slow playback and reverse frame advance playback.
[0040]
[Means for Solving the Problems]
In order to achieve the above object, the present invention provides a playback device for playing back a recording medium on which image data composed of at least an I picture, a P picture, and a B picture is recorded, and a playback unit that plays back the image data from the recording medium. A decoding unit that decodes the reproduced image data, and at the time of backward reproduction, the image data to be decoded is arranged before the I picture in the first GOP to which the image data to be decoded belongs. It is determined whether or not it is a picture, and when it is determined that the B picture is arranged before the I picture , the entry point of the second GOP arranged immediately before the first GOP The playback means is controlled to access.
In addition, the control unit performs control so as not to decode the B picture in the second GOP when obtaining a predicted image necessary for decoding the image data to be decoded first.
The reverse reproduction is reverse frame advance reproduction or reverse slow reproduction.
Further, in a reproducing apparatus for reproducing a recording medium on which image data encoded using predictive encoding is recorded, reproducing means for reproducing the image data from the recording medium, and decoding means for decoding the reproduced image data In reverse playback, a reference image necessary for decoding image data to be decoded refers to an image belonging to the second GOP arranged immediately before the first GOP to which the image data to be decoded belongs. If it is determined that the image is encoded with reference to an image belonging to the second GOP arranged immediately before the first GOP, the second Control means for controlling the reproducing means to access the entry point of the GOP.
[0041]
[Action]
According to the present invention, in reverse playback that is reverse frame advance playback or reverse slow playback, the image data to be decoded is arranged before the I picture in the first GOP to which the image data to be decoded belongs. In the case of a B picture, the playback means is controlled to access the entry point of the second GOP arranged immediately before the first GOP.
In addition, the control unit performs control so as not to decode the B picture in the second GOP when obtaining a predicted image necessary for decoding the image data to be decoded first.
In reverse playback, a reference image necessary for decoding image data to be decoded is an image belonging to the second GOP arranged immediately before the first GOP to which the image data to be decoded belongs. If it is coded with reference, the playback means is controlled to access the entry point of the second GOP.
[0042]
【Example】
FIG. 1 shows the configuration of a first embodiment of an encoded data decoding apparatus that embodies the reproducing apparatus of the present invention.
In the encoded data decoding apparatus shown in this figure, data recorded on the optical disk 60 is reproduced by a pickup 61.
The pickup 61 reads the data recorded on the optical disc 60 and supplies the output signal to the demodulation circuit 62. The demodulation circuit 62 demodulates the reproduction signal output from the pickup 61 and supplies it to the ECC circuit 63.
The ECC circuit 63 performs error detection / correction on the input data and sends it to the demultiplexer 21.
[0043]
The header separation circuit 22 provided in the demultiplexer 21 separates the pack header, packet header, and the like from the data sent from the ECC circuit 63 and supplies them to the control device 24 and is time-division multiplexed. Data is supplied to the input terminal G of the switching circuit 23. The output terminals H1 and H2 of the switching circuit 23 are connected to the input terminals of the video decoder 25 and the audio decoder 26, respectively.
[0044]
Further, the control device 24 provided in the demultiplexer 21 reads information on entry points (entry packet information) from the data input from the header separation circuit 22 and sends the information to the controller 67. Information about this entry point is stored in the entry point storage unit 41 in the controller 67. Since the controller 67 is supplied with information on the current reading position from the drive control circuit 69, the controller 67 associates the position of the entry point with the contents of the information on the current reading position, and enters the entry point storage unit 41. Can be remembered.
[0045]
Further, the control device 24 sequentially connects the input terminal G and the output terminals H1 and H2 of the switching circuit 23 according to the stream id information in the packet header supplied from the header separation circuit 22, and time-division multiplexed data. The video data is supplied to the video decoder 25 and the audio data is supplied to the audio decoder 26, respectively.
In this way, the video data separated by the demultiplexer circuit 64 is input to the video decoder 25 and decoded, and the audio data is input to the audio decoder 26 and decoded. Is output.
[0046]
Incidentally, the video data supplied from the demultiplexer 21 to the video decoder 25 is input to the video code buffer 121 in the video decoder 25 and the data is temporarily stored.
The data read from the video code buffer 121 is input to the picture header detection circuit 122, and the data sent from the video code buffer 121 to the video decoding circuit and the frame memory 125 is analyzed in the picture header detection circuit 122. And GOP headers are detected.
The contents of the picture header are sent to the controller 67 as picture header information. The picture header information indicates temporal reference (TR) information indicating the screen order in the GOP and any picture in I, P, and B. It consists of picture type information.
Note that the picture header described in this embodiment is picture_header defined by ISO11172-2 (MPEG1 Video) and ISO13818-2 (MPEG2 Video).
[0047]
Next, the data from the picture header detection circuit 122 is supplied to the picture selection circuit 123, and the movable contact P of the switch is switched to the fixed contact Q1 or the fixed contact Q2. It is sent to the decoding circuit and frame memory 125.
[0048]
That is, when the movable contact P is connected to the fixed contact Q1, the data is sent to the video decoding circuit and the frame memory 125, and when the movable contact P is connected to the fixed contact Q2, the data is It is not sent to the video decoding circuit and frame memory 125 but discarded. Although the switching condition of the movable contact P is instructed from the controller 67, the switching of the movable contact P is performed in synchronization with the detection signal from the picture header detection circuit 122.
Therefore, data of a specific picture can be selectively sent to the video decoding circuit and the frame memory 125.
[0049]
The video decoding circuit and frame memory 125 decompresses the compressed video data sent from the video code buffer 121 through the picture header detection circuit 122 and the picture selection circuit 123 and outputs the decompressed video data to the external frame memory 131.
In this embodiment, the video decoding circuit and frame memory 125 decompresses compressed data based on ISO13818-2 (MPEG2 Video), and therefore has at least three frame memories inside.
[0050]
By the way, the external frame memory 131 holds the video signal sent from the video decoder 25 by the picture hold command signal from the controller 67. When this picture hold command signal is at a low level, the video signal sent from the video decoder 25 is written for each screen and output as it is. When the picture hold command signal from the controller 67 becomes high level, the data of the picture that was output last is held, and thereafter, the held picture data until the picture hold command signal returns to low level again. Will be output.
That is, the same image is displayed continuously.
[0051]
When an instruction for reproduction or the like is given from the user to the encoded data decoding device, the controller 67 sends a control command to the video decoder 25 and the audio decoder 26 and gives an access command to the drive control device 69.
The drive control device 69 drives the pickup 61 using the tracking servo circuit 70 in accordance with a command from the controller 67 and accesses the disk 60.
Further, the drive control device 69 supplies the current read position information accessed to the controller 67.
[0052]
Next, the operation when normal reproduction and subsequent reverse frame advance are performed in the encoded data decoding apparatus shown in FIG. 1 will be described.
Of the reverse playback, reverse slow playback, reverse constant speed playback, and reverse high speed playback can be realized by an operation in which reverse frame advance is repeated at appropriate intervals. Although only the embodiment will be described, other reverse reproduction can be similarly realized within the range of speeds permitted by the processing speed of the constituent elements.
[0053]
When normal playback is instructed by the user, the controller 67 gives a command to the drive control circuit 69 to start supplying data.
In this case, if the start position of data supply on the disk 60 is designated by the user, the designated position is set as the start position, and if not, it starts from the first data recorded on the disk 60.
The drive control circuit 69 to which the command is given controls the tracking servo circuit 70 to drive the pickup 61, and the disk 60 is accessed. The pickup 61 sends the signal read from the disk 60 to the demodulation circuit 62, and the demodulation circuit 62 demodulates the reproduction signal output from the pickup 61 and outputs it to the ECC circuit 63.
Further, the ECC circuit 63 detects and corrects data errors and supplies data to the demultiplexer 21.
[0054]
When the supply of data is started, the drive control device 69 supplies the current read position information to the controller 67.
The header separation circuit 22 of the demultiplexer 21 to which the data is supplied from the ECC circuit 63 separates the pack header and the packet header from the data sent from the ECC circuit 63 and supplies them to the control device 24. The time-division multiplexed data is supplied to the input terminal G of the switching circuit 23.
[0055]
In addition, the control device 24 of the demultiplexer 21 performs time division multiplexing by sequentially connecting the input terminal G and the output terminals H1 and H2 of the switching circuit 23 according to the stream_id information of the packet header supplied from the header separation circuit 22. The video data is supplied to the video decoder 25 and the audio data is supplied to the audio decoder 26.
Further, the control device 24 of the demultiplexer 21 reads information on entry points (information on entry packets) from the data input from the header separation circuit 22 and sends the information to the controller 67. Information about this entry point is stored in the entry point storage unit 41.
[0056]
The video data separated by the demultiplexer circuit 64 is input to the video decoder 25, and the audio data is input to the audio decoder 26, from which the decompressed signals are output.
That is, the data input to the video decoder 25 is temporarily stored in the video code buffer 121, and the data read from the video code buffer 121 is passed through the picture header detection circuit 122 and the picture selection circuit 123 through the video decoding circuit and the frame memory 125. The compressed video data is decompressed to be the original video data.
[0057]
During normal playback, the picture hold command signal supplied from the controller 67 to the external frame memory 131 is at a low level, and the video signal sent from the video decoder 25 is output as it is.
In this way, a moving image is reproduced in the case of normal reproduction.
At this time, the entry point storage unit 41 of the controller 67 stores information (entry packet information) on the entry point supplied from the control device 24 of the demultiplexer 21 at the current read position supplied from the drive control circuit 69. It is stored in association with the content of information.
The controller 67 always receives the picture header information sent from the picture header detection circuit 122, and the latest information is held.
[0058]
Here, when a reverse frame advance is instructed by the user, the controller 67 starts preparation for reverse frame advance.
That is, first, the picture hold signal to the external frame memory 131 is set to a high level to hold the picture that was output last.
Next, from the information about the entry point and the latest picture header information stored during normal playback, the temporal reference information of the picture to be displayed first, and the entry point of the GOP to which the picture belongs on the disk 60 Determine the position.
When the picture to be displayed first is determined, the controller 67 enters a reverse frame advance operation.
[0059]
A flowchart of the reverse frame advance operation of the controller 67 is shown in FIG. 2, and the operation of the reverse frame advance controller 67 will be described with reference to the reverse frame advance operation flowchart.
In this operation flowchart, when reverse frame advance is started, a picture to be displayed is loaded in step S10, and then a picture to be displayed is displayed in step S20. Further, it is determined in step S30 whether or not a command for performing reverse frame advance is input from the user. If it is determined that an instruction for reverse frame advance is input, the process proceeds to step S40 and the next to be displayed. A (new) picture determination operation is performed. When the next (new) picture determination work is completed, the process returns to step S10, and the processes of steps S10 and S20 are performed to display the previous frame image. In addition, the work process of step S10 thru | or step S40 is performed circularly.
[0060]
As a result, reverse frame advance is sequentially performed.
Here, a picture to be displayed is called a target picture, a GOP to which the target picture belongs is called a target GOP, and a GOP entry point position accessed for decoding the target GOP is called an access position.
Then, the work in the operation flowchart shown in FIG. 2 can be paraphrased as a target picture load work, a target picture display work, a user command wait, and a next (new) picture determination work.
[0061]
Next, FIG. 3 shows a target picture loading flowchart in the target picture loading operation of the controller 67 performed in step S10 of the operation flowchart.
When the target picture loading flowchart is started, in step S100, the controller 67 sends a seek command to the drive control circuit 69 so that a seek operation to the access position is performed. In this case, if the access position is not defined at the beginning of the reverse frame advance operation, the position of the GOP entry point to which the target picture (picture to be displayed first) belongs is used as the access position.
[0062]
Next, the process proceeds to step S110 and waits until a picture header is detected. That is, as in normal playback, the data read from the designated position on the disc 60 is processed in each block and sent to the picture header detection circuit 122 of the video decoder, where picture type information and temporal Reference information is extracted and sent to the controller 67 to wait for detection of picture header information. When the picture header is detected, it is determined whether or not the GOP to which the picture header detected in step S120 belongs is the target GOP.
[0063]
Here, when the GOP in which the picture header is detected is different from the target GOP, when the B picture used by referring to the previous GOP picture at the time of decoding is set as the target picture, the access position of the target GOP This is when the previous GOP is specified.
Therefore, if the detected GOP is different from the target GOP, the process branches to step S160 to determine whether or not the detected picture is a B picture. If the detected GOP is determined to be a B picture, the picture selection circuit 123 is determined. By operating the movable contact P to be connected to the fixed contact Q2, the B picture data is discarded. Then, the process returns to step S110 via step S180, and again enters a picture header detection wait state.
[0064]
If the picture detected in step S160 is determined to be an I picture or a P picture, the process proceeds to step S170, where the movable contact P of the picture selection circuit 123 is operated to be connected to the fixed contact Q1, thereby decoding the picture. After the processing is performed, the process returns to step S110 via step S180, and returns to the picture header detection wait state.
As described above, in the case of an I picture or a P picture, a decoding process is performed on a picture that does not need to be displayed in order to create a predicted picture for decoding a subsequent picture. However, since it is not the target picture, the picture hold signal to the external frame memory 131 is kept at a high level so that display is not performed.
[0065]
Next, if it is determined that the GOP detected in step S120 matches the target GOP, whether or not the temporal reference value of the picture detected in step S130 matches the temporal reference value of the target picture. Is judged. If it is determined that they match, the movable contact P of the picture selection circuit 123 is connected to the fixed contact Q1 in step S140, and the picture data is sent to the video decoding circuit and the frame memory 125 for decoding processing. After being stored in the frame memory, the picture loading operation is completed.
[0066]
If the temporal reference value of the picture detected in step S130 does not match the temporal reference value of the target picture, the process proceeds to step S160 and it is determined whether or not the detected picture is a B picture. When the B picture is determined and the B picture is determined, the B picture is discarded and the process returns to the picture header detection waiting state.
Further, if it is not determined that the picture is a B picture in step S160 and the detected picture is an I picture or a P picture, a decoding process is performed in step S170 as described above, and then a picture header detection wait state is entered. Return. This is because in the case of an I picture or a P picture, it is necessary to perform a decoding process on a picture that does not need to be displayed in order to create a predicted picture for a later picture. Since it is not necessary to perform display, the picture hold signal to the external frame memory 131 is kept at the high level.
[0067]
When the picture selection circuit 123 detects an I picture, the temporal reference value of the picture, that is, the first I picture of the GOP is stored. This is for obtaining information to be used in the next work for determining a picture to be displayed, which will be described later.
Furthermore, as will be described later in the determination of the picture to be displayed, when the last display order picture of the GOP before the GOP displayed immediately before is specified as the target picture, the specific temporal reference value is not known. Is set to “$ FFFF” for the end. Thus, when the temporal reference value of the target picture is “$ FFFF” indicating the last picture of the previous GOP, the maximum temporal reference (TR) value in the GOP is detected in step S180. Then, the process proceeds to step S190. In this step S190, the maximum temporal reference value is held. If the head of the next GOP after the target GOP, that is, the second I picture or GOP header is detected, it is detected so far. The maximum temporal reference value is updated to the original temporal reference value of the target picture, and the target picture loading operation is repeated from the beginning.
[0068]
Next, FIG. 4 shows a flowchart of the target picture display operation of the controller 67 performed in step S20 of the reverse frame advance operation flowchart.
In this case, in this flowchart, the display image holding operation is performed by the external frame memory 131. Therefore, in step S200, the target picture is displayed in the external frame memory 131 from the controller 67 in step S200. The picture hold signal is set to the low level once, and then, in step S210, the operation of returning the picture hold signal to the external frame memory 131 to the high level is performed and the process is ended.
[0069]
Next, FIG. 5 shows a flowchart of the next (new) target picture determination operation of the controller 67 performed in step S40 of the reverse frame advance operation flowchart. Here, as information for specifying the next (new) target picture, the temporal reference value and access position of the next (new) target picture are determined.
When the next (new) target picture determination operation is started, it is determined in step S300 whether or not the temporal reference (TR) value of the current target picture is “0” (zero). In step S310, “$ FFFF” indicating the last picture of the GOP immediately before the current target picture is set as the temporal reference value of the new target picture, and the new access position is set as the new access position. The position of the entry point immediately before the entry point of the target GOP so far is read from the entry point storage device 41 and determined.
[0070]
Next, a new target picture is confirmed in step S320. That is, the temporal reference value of the new target picture is adopted as the temporal reference value of the target picture, and the new access position is adopted as the access position. Step S10 shown in FIG. And used in step S20.
If it is determined in step S300 that the temporal reference value of the target picture is greater than “0” (zero), whether the temporal reference value of the first I picture of the GOP to which the target picture belongs is known in step S330. If it is determined whether or not it is known, the process proceeds to step S340.
[0071]
Then, in step S340, the magnitude relation between the temporal reference value of the current target picture and the temporal reference value of the first I picture of the GOP to which the current target picture belongs is determined.
In this case, if it is determined that the temporal reference value of the current target picture is the same as or smaller than the temporal reference value of the first I picture to which the GOP target picture belongs, the I picture is known in step S330. The process proceeds to step S360 as in the case where it is determined that there is not, and the number decremented by “1” from the temporal reference value of the target picture so far is set as the temporal reference value of the new target picture. Further, as the new access position, the position of the entry point of the GOP immediately before the target GOP so far is determined by being read from the entry point storage device 41, the process proceeds to step S320, and the operation in step S320 is performed. The work is finished.
[0072]
On the other hand, if it is determined that the temporal reference value of the current target picture is larger than the temporal reference value of the first I picture to which the current target picture of the GOP belongs, the process proceeds to step S350, where As the reference value, the number decremented by “1” from the temporal reference value of the target picture so far is set. Further, as the new access position, the previous access position, that is, the position of the previous entry point of the target GOP is used as it is, and the operation proceeds to step S320 and the operation in step S320 is performed, and the operation is completed.
[0073]
Then, the reverse frame advance is realized by repeating the various operations described above, that is, the target picture load operation, the target picture display operation, the user command waiting, and the next (new) target picture determination operation.
[0074]
FIG. 6 is a block diagram showing the configuration of the second embodiment of the present invention.
In the second embodiment shown in this figure, even if the external frame memory 131 is omitted by operating the video decoding circuit and the frame memory 125 in the first embodiment, the same as in the first embodiment. In addition, reverse frame advance can be realized.
As shown in FIG. 6, the video decoding circuit and the frame memory 125 in the first embodiment internally include a video decoding circuit 132, a frame memory write control switch 126, an internal frame memory (FM) a127, an internal frame memory ( FM) b 128, an internal frame memory (FM) c 129, and a frame memory read control switch 130.
[0075]
In other words, in normal reproduction, the frame memory write control switch 126 and the frame memory read control switch 130 are controlled according to the picture type detected by the detection circuit of the picture header detection circuit 122 as shown in the timing of FIG. , I picture, P picture, and B picture can be decoded and displayed in the correct display order.
[0076]
The switching timing of the write control switch 126 and the read control switch 130 will be described. First, the I picture I ₂ is decoded and output from the video decoding circuit 132. At this time, the write control switch 126 is switched to the contact a. Therefore, the I picture I ₂ is stored in the frame memory a127. Next, the B picture B ₀ is decoded with reference to the I picture I ₂ stored in the frame memory a 127 and the P picture of the immediately preceding GOP (not shown), via the write control switch 126 whose contact is switched to c. And stored in the frame memory c129. At this time, since the read control switch 130 is switched to the contact c, the B picture B ₀ is read and sent to the display.
[0077]
Subsequently, the B picture B ₁ is decoded with reference to the I picture I ₂ stored in the frame memory a 127 and the P picture of the immediately preceding GOP (not shown), and the write control switch 126 whose contact is switched to c is changed. Is stored in the frame memory c129. At this time, since the read control switch 130 is switched to the contact c, the B picture B ₁ is read and sent to the display.
Further, the P picture P ₅ is decoded with reference to the I picture I ₂ stored in the frame memory 16a, and is written into the frame memory b 128 via the write control switch 126 switched to the contact point b. At this time, the read control switch 130 switches to the contact a, and the I picture I ₂ is output and sent to the display.
[0078]
Then, B picture B ₃ is decoded with reference to P picture P ₅ stored in the I-picture I _2, and the frame memory b128 are stored in the frame memory A127, a control write the contacts are switched to c It is stored in the frame memory c129 via the switch 126. At this time, since the read control switch 130 is switched to the contact c, the B picture B ₃ is output and sent to the display.
[0079]
Subsequently, the write control switch 126 and the read control switch 130 are sequentially switched at the timing shown in FIG. 7, and B ₀ → B ₁ → I ₂ → B ₃ → B ₄ → P ₅ →... From the frame memory. Are read out in the order of the pictures and sent to the display.
In this way, the read control switch 130 is controlled so that the picture order is rearranged and sent to the display in the original picture order shown in 20 (a).
[0080]
In the second embodiment shown in FIG. 6, the controller 67 controls the frame memory write control switch 126 and the frame memory read control switch 130, thereby effectively using the frame memory during reverse frame advance. The external frame memory 131 is unnecessary.
Therefore, the video decoding circuit and the frame memory which are different from the first embodiment will be described, and the description of the other parts will be omitted.
[0081]
The video decoding circuit 132 in the second embodiment performs an operation for expanding the compressed video data in units of pictures. At this time, when decompression using inter-frame correlation is performed, such as P picture and B picture, it is possible to decode by referring to data stored in the internal frame memories a127, b128, and c129. ing. Then, the video data decoded by performing arithmetic processing in the video decoding circuit 132 is sent to the frame memory write control switch 126.
[0082]
The frame memory write control switch 126 switches the contact w to the contacts a, b, and c in response to an instruction from the controller 61, thereby converting the video data sent from the video decoding circuit 132 to the internal frame memories a127, b128, and c129.
The internal frame memories a127, b128, and c129 store (accumulate) the video data sent from the frame memory write control switch 126 and output the video data read via the frame memory read control switch 130. .
That is, the frame memory read control switch 130 is stored in an arbitrary frame memory among the internal frame memories a127, b128, and c129 by switching the contact z to a, b, and c in accordance with an instruction from the controller 61. Output frames.
[0083]
In normal reproduction, control is performed as described above with reference to the timing chart of FIG. 7, but the controller 67 obtains the picture type of the detected picture from the picture header detection circuit 122 every time a picture header is detected, and Thus, the frame memory write control switch 126 and the frame memory read control switch 130 are controlled.
[0084]
When a reverse frame advance is instructed by the user, the frame memory read control switch 130 is fixed to the currently selected terminal instead of performing a picture hold operation using the external frame memory 131. Hold the picture.
As described above, in the second embodiment, one of the three planes of the internal frame memory is used for holding a picture. Therefore, in the reverse frame advance operation, the target picture is loaded on the remaining two planes. There is a need to do. In this case, if the B picture is not decoded, the decoding operation can be continued on the two sides by alternately storing the I and P pictures on the remaining two sides.
[0085]
If the target picture is a B picture, an internal frame memory on the third side is required when decoding the target picture. In this case, the target picture has been used to hold the picture until the target picture is displayed. A new target picture may be overwritten on the internal frame memory while the internal frame memory is selected as the display picture.
Since the screen is disturbed when writing and reading are performed simultaneously, the data writing to the internal frame memory is delayed by one field from the phase of the data reading from the internal frame memory so that the screen is not disturbed.
[0086]
The flowchart of the reverse frame feed operation of the controller 67 in the second embodiment is as shown in FIG. 2 as in the first embodiment.
That is, the target picture loading work, the target picture display work, the user command waiting, and the next picture determining work are repeated.
[0087]
Next, FIG. 8 shows a flowchart of the target picture loading operation of the controller 67 in the second embodiment.
Since this flowchart is also almost the same as FIG. 5, only different parts will be described.
A different part is that the decoding process in step S140 is not performed. In other words, if it is determined that the detected GOP is the same as the target GOP, and the temporal reference value of the detected picture matches the temporal reference value of the target picture, no processing is performed. The picture loading operation is finished as it is.
[0088]
Further, although not shown in the flowchart, it is determined that the temporal reference value of the detected picture does not match the temporal reference value of the target picture, and the detected picture is determined to be an I picture or a P picture. If this is the case, the decoding process is performed in step S170, but the remaining two frame memories other than the internal frame memory used for picture hold are alternately used as the internal frame memory in which the decoding result is written. This switching is performed by operating the frame memory write control switch 126. In addition, the frame memory read control switch 130 keeps the internal frame memory used for picture hold selected so that an I picture or P picture image being decoded is not displayed.
[0089]
Next, a flowchart in the target picture display operation of the controller 67 is shown in FIG.
In the second embodiment, the target picture display operation is performed by decoding the detected picture in step S400 and overwriting the internal frame memory used for picture hold.
Further, since the flowchart of the target picture determination operation is the same as that in FIG. 5, the description thereof is omitted.
[0090]
As described above, the second embodiment in which the external frame memory 131 is omitted by controlling the timing for performing the frame memory write control and read control and the target picture decoding process is the same as in the first embodiment. It is possible to perform reverse frame advance.
[0091]
In the first and second embodiments of the present invention described above, as the reverse frame advance processing procedure, as shown in FIG. 2, after receiving a command from the user, the target picture determination work, the target picture Loading work and display work.
However, according to this method, since each process is performed after receiving a command from the user, it takes time until the screen is updated from the user's command, and the image is displayed with a delay. .
In particular, it takes time to load the target picture.
[0092]
A third embodiment capable of improving this problem will be described with reference to the flowchart shown in FIG.
In the third embodiment, the process of determining the target picture and the process of loading the target picture are performed in advance in step S500 without waiting for an instruction from the user, and the process waits for an instruction from the user in step S510. If it is determined in step S510 that there is a command from the user, the target picture is displayed in step S520. When this display operation is completed, the next target picture determination operation is immediately performed in step S530, and the target picture loading operation is performed in step S500, and a command standby state from the user in step S510 is set via step S500. The
[0093]
Thereby, it becomes possible to almost eliminate the reaction time from the user's command input to the display. In general, when a user issues a reverse frame feed operation command, the interval between the reverse frame feed commands of the user is not performed in a very short time, for example, about once per second. In the third embodiment, it is possible to realize a reverse frame feed function with almost no waiting time.
In the above description, reverse frame advance has been described. Of reverse playback, reverse slow playback, reverse constant speed playback, and reverse high speed playback are realized by repeating reverse frame feed at appropriate intervals. Therefore, the present invention described above can also be applied to other reverse reproduction.
[0094]
【The invention's effect】
As described above, the present invention stores the currently decoded entry point and extracts the immediately preceding entry point so as to specify the frame to be sent to the decoding. It is possible to reproduce moving image data composed of frames compressed using difficult inter-frame correlation in the reverse direction.
In addition, since decoding is started from the I picture located at the head of the GOP, even if there is no data necessary for decoding in the frame memory, all frames (frames) can be displayed. Direction playback, reverse slow playback, and reverse frame advance playback can be performed.
[0095]
Furthermore, in the process of detecting data to be displayed next, unnecessary frames are discarded and frames necessary for the next frame to be decoded are decoded, so that all pictures including B pictures can be quickly reversed. You will be able to play.
Furthermore, if the operation up to immediately before the display is performed before the user's command is input, the reverse frame feed can be displayed without a time delay in response to the user's command.
[Brief description of the drawings]
FIG. 1 is a block diagram showing a configuration of a first embodiment of a coded data decoding apparatus embodying a reproducing apparatus of the present invention.
FIG. 2 is a flowchart executed by a controller during a reverse frame advance operation in the first embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 3 is a flowchart of a target picture loading operation performed by a controller during a reverse frame advance operation in the first embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 4 is a flowchart of the target picture display operation performed by the controller during the reverse frame advance operation in the first embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 5 is a flowchart of the next picture determination operation performed by the controller during the reverse frame advance operation in the first embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 6 is a block diagram showing the configuration of a second embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention.
FIG. 7 is a diagram showing the write and read timings of the frame memory of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention.
FIG. 8 is a flowchart executed by a controller at the time of reverse frame feed operation in the second embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 9 is a flowchart of a target picture display operation performed by the controller during a reverse frame advance operation in the second embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 10 is a flowchart executed by a controller during reverse frame advance operation in the third embodiment of the encoded data decoding apparatus embodying the reproducing apparatus of the present invention;
FIG. 11 is a diagram illustrating a data format in a unit of a conventional multiplexed bit stream.
FIG. 12 is a diagram showing a table of stream IDs constituting a part of a packet header.
FIG. 13 is a block diagram showing a configuration of a conventional encoded data decoding apparatus.
FIG. 14 is a conceptual diagram illustrating a configuration of a bitstream including an I picture, a P picture, and a B picture.
FIG. 15 is a block diagram showing a configuration of another conventional encoded data decoding apparatus.
FIG. 16 is a block diagram showing a configuration of yet another conventional encoded data decoding apparatus.
FIG. 17 is a diagram illustrating an example of a data format in still another encoded data decoding apparatus in the related art.
FIG. 18 is a diagram illustrating another example of a data format in still another conventional encoded data decoding apparatus.
FIG. 19 is a diagram showing a structure of a program stream directory defined in the MPEG2 system.
FIG. 20 is a diagram illustrating the structure of inter-frame prediction and the structure of a recording frame in MPEG.
[Explanation of symbols]
21 Demultiplexer 22 Header separation circuit 23 Switching circuit 24 Control circuit 25 Video decoder 26 Audio decoder 41 Entry point storage unit 60 Disk 61 Pickup 62 Demodulation circuit 63 ECC circuit 69 Drive control circuit 67 Controller 70 Tracking servo circuit 121 Video code buffer 122 Picture Header detection circuit 123 Picture selection circuit 125 Video code circuit and frame memory 126 Frame memory write control switch 127, 128, 129 Frame memory 130 Frame memory read control switch 131 External frame memory 132 Video decode circuit

Claims (6)

In a playback apparatus for playing back a recording medium on which image data consisting of at least an I picture, a P picture, and a B picture is recorded.
A reproducing unit for reproducing the image data from said recording medium,
A decoding unit for decoding the reproduced image data;
At the time of reverse reproduction, it is determined whether or not the image data to be decoded is a B picture arranged before the I picture in the first GOP to which the image data to be decoded belongs. A control unit that controls the reproducing means to access an entry point of a second GOP arranged immediately before the first GOP when it is determined that the B picture is arranged before; A playback device comprising:   The control unit controls the B picture in the second GOP not to be decoded when obtaining a predicted image necessary for decoding the image data to be decoded first. The reproducing apparatus according to 1.   3. The playback apparatus according to claim 2, wherein the reverse playback is reverse frame advance playback or reverse slow playback. In a playback apparatus for playing back a recording medium on which image data encoded using predictive encoding is recorded,
Reproducing means for reproducing the image data from said recording medium,
Decoding means for decoding the reproduced image data;
At the time of backward reproduction, a reference image necessary for decoding image data to be decoded refers to an image belonging to the second GOP arranged immediately before the first GOP to which the image data to be decoded belongs. The second GOP is determined by referring to an image belonging to the second GOP arranged immediately before the first GOP. And a control means for controlling the playback means to access the entry point. In a reproduction method for reproducing a recording medium on which image data consisting of at least an I picture, a P picture, and a B picture is recorded,
A reproduction step of reproducing image data from the recording medium;
A decoding step of decoding the reproduced image data;
At the time of backward reproduction, it is determined whether or not the image data to be decoded is a B picture arranged before the I picture in the first GOP to which the image data to be decoded belongs. A control step for controlling the reproduction step to access the entry point of the second GOP arranged immediately before the first GOP when it is determined that the B picture is arranged before.
A playback method characterized by comprising: In a reproduction method for reproducing a recording medium on which image data encoded using predictive encoding is recorded,
A reproduction step of reproducing image data from the recording medium;
A decoding step of decoding the reproduced image data;
At the time of reverse reproduction, a reference image necessary for decoding image data to be decoded refers to an image belonging to the second GOP arranged immediately before the first GOP to which the image data to be decoded belongs. If it is determined that it is encoded with reference to an image belonging to the second GOP arranged immediately before the first GOP, the second GOP Control step for controlling the playback step to access the entry point
A playback method characterized by comprising:

Images