JP2002010213A - Method and device for reproducing encoded data - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reproducing device and method which can implement backward reproduction of an encoded data such as MPEG per unit of picture. SOLUTION: When a nth picture in a mth picture structure group is instructed to be reproduced backward during decoding, a (n-1)th picture is decoded. When (n-1) is 2 or more, decoding is implemented from the first picture in mth picture structure group as the (n-1)th picture. When (n-1) is 1 or 0, decoding is implemented from the first picture in (m-1)th picture structure group as the (n-1)th picture. The backward reproduction per unit of picture can be implemented even if the first type of picture is I picture and the second type of picture is B or P picture.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a reproducing method for reproducing encoded video data recorded on a storage medium such as a hard disk, and a reproducing apparatus for encoded video data. The present invention relates to a method of reproducing encoded data and an apparatus for reproducing encoded data, which make it possible.

[0002]

2. Description of the Related Art Moving picture image coding (MPEG) has been widely used as a means for efficiently encoding a long moving picture.
Experts Group).

The MPEG encoding algorithm is based on temporal information compression by motion compensation, that is, a frame (picture).
Inter compression is used. In order to efficiently perform editing and random access, a GOP (Group Of Pictur) is a picture structure group in which a plurality of pictures are grouped together.
e) is a unit, and a unit obtained by adding a sequence header to the head of the GOP is configured as an access unit.

[0004] The GOP is of a first type, ie, an I (Intra) picture which is an intra-frame (picture) intra-coded video, and a second type, ie, a P (Predictive) which is a forward predictive encoded video between frames (pictures). It is composed of a picture and a second type, that is, B (Bidirectionally predictive), which is an inter-frame (picture) bidirectional predictive encoded video. I-pictures can be decoded from the picture itself without reference to other pictures when decoding,
It is added to the head of the GOP. The P picture is decoded with reference to a temporally previous I picture or P picture. The B picture is decoded with reference to the I picture or the P picture in both the temporally preceding and succeeding directions.

FIG. 11 shows the I picture, P picture, and B picture.
FIG. 4 is an explanatory diagram showing a relationship between a state of a picture on a recording medium and a state after decoding. (A) The figure shows encoded data on a recording medium,
(B) shows a video signal arrangement after the decoding. (A)
In the figure, three GOPs are shown together with a sequence header. One GOP is composed of the first GOP header and 12
Are shown, and a picture header is added to the head of each picture.

(A) In the figure, I indicates an I picture, B indicates a B picture, P indicates a P picture, and the numbers in parentheses indicate frame (picture) numbers. The recording direction is, for example, the direction from left to right in the diagram (a). The video signal after decoding is the same as the recording direction during forward reproduction, as shown in the diagram (b), in the order of frame (picture) number. They are arranged and displayed on the display monitor in this order. (A) In the example of the figure, GO
There is one I picture at the beginning of P, and then B, B,
Each picture of P, B, B, P, B, B, P, B, B is recorded. There are eight B pictures and two P pictures.

[0007]

In the case of decoding encoded data as described above, during normal reproduction in the forward direction, decoding can be performed in the correct order by decoding in the forward direction. In this case, even if the decoding order of the pictures in the GOP is simply reversed, there is a problem in that decoding is inconvenient. In FIG. 11 as an example, to decode B (9) having picture number 9, P (8) having picture number 8 and P (8) having picture number 11 can be decoded.
(11), P (5) is required to decode P (8), and P (5) is
(2) is required. Therefore, even if the decoding order is reversed, decoding cannot be performed correctly.

As a method for solving this problem, Japanese Patent Application Laid-Open
No. 46712 has been proposed. This discloses a decoding method in which encoded data of the MPEG system recorded on a storage medium is reproduced in a backward direction using only a frame memory necessary for a forward reproduction. However, the reproduced video is only an I picture or a P picture, and a B picture is not reproduced. Therefore, it has not been possible to realize the reproduction in the backward direction on a picture basis.

In addition, Japanese Patent Application Laid-Open No. H11-136638 has been proposed. For this purpose, a reverse playback method in picture units has been proposed.
Since the number of frame memories required is equal to the number of pictures constituting the OP, there is a problem that the cost increases.

The present invention has been made to solve the above-mentioned problem. Even if the first type of picture is an I picture and the second type of picture is a B picture or a P picture, the inverse of the picture unit is used. The present invention proposes a new encoded data reproducing method capable of reproducing in the direction.

Further, according to the present invention, the first type of picture is I
The present invention proposes a new encoded data reproducing apparatus that can perform reverse reproduction in picture units even if the second type of picture is a B picture or a P picture.

Further, according to the present invention, the first type of picture is I
Even if the second type of picture is a B-picture or a P-picture, a new and improved method that can calculate the read start position of coded data more easily in picture units and perform reverse playback in picture units The present invention proposes a reproducing apparatus for encoded data.

Further, the present invention provides a method of reproducing a picture in the backward direction using a smaller number of frame memories even if the first type of picture is an I picture and the second type of picture is a B picture or a P picture. The present invention proposes a new encoded data reproducing apparatus capable of performing the following.

[0014]

A method of reproducing encoded data according to the present invention includes a plurality of picture structure groups recorded on a recording medium, and each of the picture structure groups is used for decoding within the picture structure group. A method of reproducing encoded data including a possible first type of picture, and a succeeding second type of picture that includes pictures that can be decoded from the picture structure group and other picture structure groups; ,
While decoding the n-th (n is a natural number of 3 or more) picture in the m-th (m is a natural number of 2 or more) picture structure group,
This is a method for decoding the (n-1) th picture of the m-th picture structure group when decoding in the reverse direction to the recording direction is instructed, and when (n-1) ≧ 2, The (n-1) th picture is decoded by decoding in the forward direction from the first picture of the first picture structure group, and when (n-1) = 1 or 0, (m-1) By decoding in the forward direction from the first picture of the first picture structure group, the (n-1)
This is a method characterized by decoding a th picture.

The encoded data reproducing apparatus according to the present invention includes a plurality of picture structure groups recorded on a recording medium, wherein each of the picture structure groups is a first type which can be decoded in the picture structure group. And a second type of picture that follows, and that is a device that reproduces encoded data including pictures that can be decoded from the picture structure group and other picture structure groups. During decoding of the n-th picture (n is a natural number of 3 or more) in the picture structure group of m or more (n is a natural number), decoding in the reverse direction to the recording direction is instructed, and ( a recording medium for decoding the (n-1) -th picture, the encoded data being recorded, a picture structure group counting means for counting the picture structure group,
Picture counting means for counting the pictures in each picture structure group, information holding means for holding information as to whether the decoding direction is the forward direction or the backward direction, and the (n-1) th picture A data read start position control means for calculating a read start position of coded data from the recording medium upon decoding;
1) When ≧ 2, the (n−1) th picture is decoded in the forward direction from the first picture of the mth picture structure group based on the operation of the data read start position control means. Decrypt and (n-
1) When (1) = 1 or 0, the (n-1) th picture is decoded by decoding in the forward direction from the first picture of the (m-1) th picture structure group It is characterized by the following.

Further, the encoded data reproducing apparatus according to the present invention, when (n-1) ≥2, decodes the (n-1) -th picture of the m-th picture structure group, When decoding the (n-2) th picture,
When decoding the (n-1) th picture, data reading from the recording medium is started using the same address as that calculated by the read start position control means, and the (n-2) th picture is decoded. Things.

Further, the encoded data reproducing apparatus according to the present invention has transfer count means for counting the number of times a predetermined amount of data is read from the recording medium, and the data read start position control means is provided with a means for controlling the data read before reverse decoding. Using the value of the transfer counter means at the time of forward decoding of
The read start position corresponding to the first picture in the m-th picture structure group is controlled.

Further, the apparatus for reproducing encoded data according to the present invention comprises a main memory having three frame memories and a sub-memory having at least one frame memory, and the n-th picture of the m-th picture structure group. When the backward decoding is instructed, the decoded data of the n-th picture in the m-th picture group is held and displayed in the frame memory of the sub-memory means, and the (n-1) -th picture is The picture is decoded using the main memory means and is displayed following the n-th picture.

[0019]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram of a coded data reproducing method and apparatus according to the present invention; Embodiment 1 FIG. FIG. 1 is a diagram showing a configuration of a reproducing apparatus according to Embodiment 1 of the present invention. In FIG. 1, 1
Reference numeral 0 denotes a recording medium in which encoded data is stored, which is a hard disk. Reference numeral 11 denotes a head, 12 denotes a hard disk control unit that controls the hard disk, and 13 denotes a signal reading unit that reads encoded data from the hard disk 10 and outputs a program stream 100.

FIG. 2 shows the structure of the program stream 100 according to the MPEG standard. FIG. 3A is an example of the program stream 100, which is configured as a pack in which one or more packets are bundled. The packet is composed of a PES payload (video stream) 101 and P
An ES payload (audio stream) 102 is included. The video stream 101 is shown in FIG. 2B and the audio stream 102 is shown in FIG. The video stream 101 has a sequence header and a GOP header corresponding to one GOP, and a plurality of pictures with picture headers are continuous with the GOP header.

FIG. 2D shows the structure of the sequence header in the video stream 101, FIG. 2E shows the structure of the GOP header in the video stream 101, and FIG. 3 shows the structure of a picture header. Since these configurations are well known, detailed description will be omitted, but it should be noted that the time code TC is included in the GOP header of FIG.

The time code TC is time information corresponding to each GOP in the GOP header. The time code TC includes the hour, minute, and second of the recording start time of the GOP viewed from the recording reference time on the recording medium 10 and the frame. The number is indicated by, for example, a total of 25 bits. For example, FIG.
OP6, 7, and 8 are exemplified, and the time code of GOP6 is indicated by 10: 10: 10: 10, which is a recording start time of 10:10:10 with respect to the recording reference time, and It means that it is a frame.

Referring back to FIG. 1, reference numeral 20 denotes a video stream 10 from the read program stream 100.
1, an audio stream 102, and system header information. The video stream 101 is sent to the video header separation unit 31 via the video buffer 30, the audio stream 102 is sent to the audio header separation unit 41 via the audio buffer 40, and the system header information is sent to the header information storage unit 50. The system header information is the pack header of FIG. 2,
This is a PES header. All the header information of the video stream 101 and all the header information of the audio stream 102 are separated by the separation units 31 and 41, sent to the header information storage unit 50, and the actual video data in the video stream 101 is converted by the video decoding unit. 32, and the actual audio data of the audio stream 102 is sent to the audio decoding unit 42.

In FIG. 1, reference numeral 60 denotes a frame memory control unit, 61 denotes a first frame memory, 62 denotes a second frame memory, 63 denotes a third frame memory, and 64 denotes a fourth frame memory. The first, second and third frame memories 61, 62 and 63 constitute a main memory MM, and the fourth frame memory 64 constitutes a sub memory SM. These frame memories 61, 62, 63,
Reference numerals 64 are each configured to store data of one frame (picture), and are controlled by the frame memory control unit 60.

In FIG. 1, the decoding output unit 70 is provided in the main memory M
It is connected to the output unit of each of the M frame memories 61, 62, and 63, and selects and outputs the output of any one of them. Video output unit 71 is L (LOW)
One of the two inputs of the side and the H (HIGH) side is selected and output. The L side input is connected to the decoding output unit 70 of the main memory MM side, and the H side input is connected to the sub memory SM. I have. A video monitor 72 displays the output of the video output unit 71.

In FIG. 1, reference numeral 80 denotes a controller for controlling the entire system, which includes a hard disk control unit 12, a header information storage unit 50, a video decoding unit 32, an audio decoding unit 42, a frame memory control unit 60, and a decoding output unit. 70, and a video output unit 71. The controller 80 is, for example, a CPU of a computer,
Upon receiving the header information from the header information storage unit 50 and the decoded video data from the video decoding unit 32, the unit controls the frame memory control unit 60, the decoding output unit 70, and the video output unit 71. The controller 80 is given a user command 110.

Frame memories 61, 62, 63, 64
Is a memory having a configuration different from that of the computer in the embodiment of FIG. 1, but may be configured using a memory built in the computer. In this case, the frame memory control unit 60 is also built in the computer.

Controller 80 also cooperates with registers or counters 80A. This register or counter group 80A includes the 16 registers or counters shown in FIG. This register or counter group 80A
Has a frame counter FC and a time code register T
C, transfer counter DC, GOP counter GC, register M, register FIRST, register MODE, register REVERSE, register FCM, register TCM, register DCM, transfer source address register A0, register COMP, register GOP FLAG, register α, and register β It is included.

The frame counter FC is a counter for counting the number of frames (pictures) in each GOP, and the time code register TC stores the time code TC of each GOP.
The transfer counter DC is a counter that counts the number of data read out from the hard disk 10 by the signal readout unit 13.
The P counter GC is a counter that counts the number of GOPs, and the register FIRST is a register that becomes 1 during a transition period after the reverse decoding is commanded and becomes 0 after this transition period. For example, the m-th register (m is 2) G of above natural number)
Reverse decoding is commanded while decoding the n-th (n is a natural number of 3 or more) picture of the OP, and when decoding the (n-1) -th picture, after the backward decoding is commanded, To decode the (n-1) th picture, the recording medium 1
The transition period is a period until the calculation of the read start position of “0” ends, and the register FIRST becomes “1”.

The register MODE is a register holding a value corresponding to the mode, the register REVERSE is 1 in the backward decoding state, and 0 in the forward decoding state, and the register FCM is a value at a certain moment of the frame counter FC. The register to be held, the register TCM is a register to hold an instantaneous value of the time code register TC, the register DCM is a register to hold an instantaneous value of the transfer counter DC, and the register COMP is to read data from the hard disk 10 at the time of reverse decoding. The register used to control the start position, the register GOP FLAG is the register that starts up in the GOP header, the register α
Is a register for holding a data transfer unit α from the hard disk 10, and a register β is a register for holding a data transfer unit β (β ≠ α) from the hard disk 10.

[Forward Decoding Operation] Now, a decoding method and a decoding operation by the decoding device configured as described above will be described. The present invention is characterized in that backward decoding is achieved in units of pictures, and a forward decoding operation will be described with reference to FIGS. 3 and 4 prior to backward decoding. FIG. 3 is a time chart in the case of performing the backward decoding after the forward decoding, and FIG. 4 is a flowchart of the operation of the controller 80 during the decoding.

FIG. 3A shows the register GOP FLAG, FIG. 3B shows the GOP number, FIG. 3C shows the time code thereof, and FIG. 3D shows the type of picture recorded on the recording medium 10 and its decoding order. Show. (E) shows the state of the first frame memory 61, (f) shows the state of the second frame memory 62, and (g) shows the state of the third frame memory 63.
(H) shows the output state of the decoding output unit 70, (i) shows the state of the frame counter FC, (j) shows the state of the transfer counter DC, (k) shows the state of the register DCM, and (l) shows the state of the forward decoding. The trajectory and (m) show the trajectory at the time of backward decoding.

Encoded data is pre-recorded as a file on the hard disk 10 as a storage recording medium. When a user command 110 to reproduce the encoded data is input to the controller 80, the controller 80 proceeds to step 200 as shown in FIG. 4A, and clears all registers and counters in preparation for reproduction. Then, the head address of the file is stored in the transfer source address register A0. Then step 2
01 advances to the transfer subroutine.

The transfer subroutine is performed by the video buffer 30
And a subroutine for controlling the reading of the encoded data from the hard disk 10 using a transfer means such as a DMA so as to sequentially monitor the accumulated amount of the encoded data buffered in the audio buffer 40 and prevent overflow or underflow. is there. This subroutine is shown in FIG.
This is shown in FIG. If it is determined in step 220 that reading of the encoded data is necessary, step 22
Proceed to 1. If it is determined that reading is not necessary, the process exits the subroutine. In the case of starting reproduction, the process proceeds to step 221 because each buffer is empty.

Next, at step 221, the controller 8
0 instructs the hard disk controller 12 to start reading from the transfer source address register A0 by the transfer unit α bytes held in the register α. Then, every time when the transfer is completed by α bytes, step 222 is executed.
Then, the transfer counter DC is incremented by 1 to exit the transfer subroutine. In step 202, the output of the video output unit 71 is set to the decoding output unit 70, and the process proceeds to step 203. At step 203, it is determined whether or not reverse reproduction is to be performed. If forward decoding is to be continued, the process returns to step 201, and proceeds to the transfer subroutine again. As described above, in the case of forward reproduction, encoded data can be continuously read from the hard disk 10, so that smooth reproduction can be performed.

Next, the flow of the read encoded data will be described. Hard disk control unit 12 receiving the command
Causes the head 11 to seek to the address value A0 of the transfer source address register A0 and start reading. The read encoded data is sent to the signal reading unit 13 and
Processing such as value conversion and error correction is performed. Then, it is sent to the system separation unit 20 as a program stream 100. As also shown in FIG.
Is composed of a pack in which one or more packets are bundled. The packet has a structure in which a video stream or an audio stream is divided into data of an appropriate length, and a header is added at the beginning.

The system separation section 20 separates such a program stream 100 into a video stream 101, an audio stream 102, and system header information. All system header information is sent to the header storage unit 50. This header information can be read by the controller 80. The audio stream 102 is sent to the audio header separation unit 41 via the audio buffer 40. Then, only the header portion is sent to the header information storage unit 50, and the remaining actual data is sent to the audio decoding unit 42. The audio data decoded by the audio decoding unit 42 is sent to a D / A converter (not shown) and output as an analog audio signal.

On the other hand, the video stream 101 is sent to the video header separation unit 31 via the video buffer 30. Then, video header information such as a sequence header, a GOP header, and a picture header is sent to the header storage unit 50, and the remaining actual data is sent to the video decoding unit 32. In the video decoding unit 32, the encoded video data is decoded according to the MPEG standard, and the decoded video data is sequentially expanded in a first frame memory 61, a second frame memory 62, and a third frame memory 63. It is sent. The data is output from the decoding output unit 70 and displayed on the video monitor 72 in the display order. In decoding, when decoding a picture that needs to refer to the decoded data of the preceding or subsequent picture or the preceding and following pictures,
The decoding is advanced while the decoded data before or after that, or the decoded data before and after that is stored in one or two of the frame memories 61, 62, and 63 are taken into the video decoding unit 32. Since the main memory MM has three frame memories, not only I pictures but also P pictures and B pictures can be decoded.

In the case of forward reproduction, the video stream 10
1 is sent to the decoding unit 32 for each picture in the order along the trajectory 101a in FIG. Taking the case where reproduction is started from the first picture of GOP6 as an example, the header storage unit 5
When the GOP header of GOP6 is written to 0, the controller 80 shifts the processing to the GOP header subroutine of FIG. When the header is written, an interrupt may be used, or the controller 80 may perform a polling process on the header information storage unit 80.

The GOP header subroutine is shown in FIG. Since the reproduction is in the forward direction, the process proceeds from step 350 to step 351 to clear the frame counter FC to zero. Then, in step 352, the GOP counter G
C is cleared to 0, and at step 353 register D
The value of the transfer counter DC is stored in the CM, and the time code stored in the header information storage unit 50 is stored in the time code register TC.

The time code is represented by G as shown in FIG.
This is time information for each GOP in the OP header. For example, the time code of GOP6 is "10:10:11:
10 ", and this value is stored in the register TC. After storing, the transfer counter DC is cleared to 0 in step 354. Then, in step 355, the register GOPFL
After setting AG to 1, exit the GOP header subroutine. The number 6 of GOP6 is provided for easy explanation of the present embodiment, and is not defined by the MPEG standard.

Next, I which is the first picture of GOP6
(2) The picture is input from the video buffer 30 to the video decoding unit 32. When the picture header is written in the header information storage unit 50, the controller 80 operates as shown in FIG.
To the picture header subroutine. In step 370, the frame counter FC is counted up by one. Since the frame counter FC is cleared to 0 each time the GOP header is input in step 351 described above, the value of the frame counter FC is determined by the order of the picture currently being decoded in the GOP. It shows.

Next, in step 371, one of the first frame memory 61, the second frame memory 62, and the third frame memory 63 is decoded and output according to the type of picture being decoded. After selection as the output of the unit 70, the subroutine is exited. Now decrypting
Since the I (2) picture can be decoded independently, the decoded video data F (2) is sent to the first frame memory 61, and the output of the decoding output unit 70 is output to the first frame memory 61.
Is selected.

Next, the B (0) picture is output to the video decoding unit 32.
Sent to In step 370, the frame counter FC counts up to FC = 2. This picture is B
Since the picture is a picture, the F (2) frame previously stored in the first frame memory 61 is referred to and sent to the third frame memory 63 as decoded video data F (0). In step 371, the output of the decoding output 70 is selected so as to be on the third frame memory 63 side.
The F (0) frame is displayed on the video monitor 72 because the output decoding output 70 of the video output unit 71 is selected.

Next, the B (1) picture is output to the video decoding unit 32.
Sent to At step 370, the frame counter FC counts up to FC = 3. This picture is also B
Since the picture is a picture, it is sent to the third frame memory 63 as decoded video data F (1) with reference to F (2) previously stored in the frame memory 61. Then, the F (1) frame is displayed on the video monitor 72 from the video output unit 71.

Next, the P (5) picture is stored in the video decoding unit 32.
Sent to In step 370, the frame counter FC counts up and becomes FC = 4. This picture is P
Since the picture is a picture, it is sent to the second frame memory 62 as decoded video data F (5) with reference to F (2) previously stored in the frame memory 61. At this time, the decoding output unit 70 is switched to the first frame memory 61 side to output F (2) and display it on the video monitor 72.

Next, the B (3) picture is output to the video decoding unit 32.
Sent to In step 370, the frame counter FC counts up to FC = 5. This picture is B
Since it is a picture, F (2) previously stored in the frame memory 61 and F (5) previously stored in the frame memory 62
Is sent to the third frame memory 63 as decoded video data F (3). And the decryption output unit 7
0 is switched to the third frame memory 63 side to output the video data F (3) and display it on the video monitor 72.

Next, the B (4) picture is output to the video decoding unit 32.
Sent to At step 370, the frame counter FC counts up to FC = 6. This picture is also B
Since it is a picture, the F stored earlier in the frame memory
Video data F after decoding with reference to (2) and F (5)
The data is sent to the third frame memory 63 as (4). Then, the decoding output unit 70 outputs the video data F (4) and displays it on the video monitor 72.

Although the subsequent steps are omitted, the forward reproduction is performed in the correct order by repeating the above-described operation. The monitoring of the data accumulation value of the video buffer 30 and the audio buffer 40 has been described in the transfer subroutine. Specifically, a target threshold value is set in advance, and the data accumulation amount is monitored. When the threshold value is exceeded, reading of encoded data from the hard disk 10 is stopped, and when the data storage amount falls below the threshold value, reading of encoded data from the hard disk 10 is performed. As a result, the video buffer 30 stores encoded data sufficient for decoding without overflow or underflow.
It is not necessary to provide a maximum capacity of 1 GOP or more.

[Reverse Playback Operation (1): Playback from F (25) to F (24)] Now, the backward decoding operation in picture units, which is a feature of the present invention, will be described. First, FIG.
, The forward decoding operation is continued, and the decoded data of the third F (25) frame of GOP 8 is stored in the third frame memory 63, and the decoded data is output to the decoding output unit 7.
0, FIG. 3 is a diagram showing a case where the user command 110 instructs reverse decoding while the video is displayed on the video monitor 72 via the video output unit 71, and F (25) to F (24) are decoded and displayed. This will be described with reference to FIG.

Generally, during decoding of the n-th (n is a natural number of 3 or more) picture of the m-th (m is a natural number of 2 or more), backward decoding is instructed, and the m-th GOP is instructed.
In this case, it is assumed that the (n-1) th picture is decoded, but in this case, the mth GOP is GOP8, the nth picture is F (25) which is the third picture, and the decoding is in progress. Is instructed to perform backward decoding, and the (n-1) th, that is, the second picture of GOP8, F (2
4).

When the reverse reproduction is performed, the next signal displayed on the video monitor 72 is an F (24) frame. When a reverse playback command 110 is input to the controller 80 from the user, step 203 in FIG.
And the process proceeds to step 210. In step 210, the register REVERSE is set to 1 and the register FIRST is set to 1. A register REVERSE is a register indicating that the reverse reproduction process is being performed.
Is a register indicating that the transition has been made from forward reproduction to reverse reproduction. This register FIRST is set to 1 by the reverse direction command 110, and the signal F to be displayed next is
The period until the calculation of the read start position of the recording medium 10 for the decoding of (24) is completed is maintained at 1, and becomes 0 when the calculation is completed.

Next, at step 211, the flow shifts to the reverse reproduction subroutine of FIG. In step 300, the video decoding unit 3
2. Pause the decoding operation of the audio decoding unit 42,
Freeze the playing video frame. The video frame being reproduced is an F (25) frame, and the freeze can be realized by repeating the output of the third frame memory 63 in frame units. Then, the transfer subroutine processing is stopped so that the video buffer 31 and the audio buffer 41 do not overflow.

Next, in step 301, the frame memory control unit 60 is instructed to copy the freeze-reproduced video data to the fourth frame memory 64. Upon receiving this, the frame memory control unit 60 sets the third frame memory 6
3 is stored in a fourth frame memory 64.
Transfer copy to. When copying is completed, step 30
At 2, the output of the video output unit 71 is switched from the decoding output unit 70 to the fourth frame memory 64 side. The switching timing of the video output unit 71 is performed during the vertical blanking period of the video output signal in order to prevent the video monitor 72 from causing any symptoms such as blurring.

Next, at step 303, a value obtained by subtracting 1 from the value of the frame counter FC is substituted for the register COMP. The register COMP indicates the value of the next picture to be displayed by the reverse playback, and thus the register COMP is
OMP = 2. Next, at step 304, the register FI
Determine the value of RST. Since FIRST = 1 now, the routine proceeds to step 310, where the value of the register COMP is determined.
Since COMP = 2 now, the process proceeds to step 311 and 3 is set in the register MODE.

Displaying the F (24) frame means that the B (24) picture, which is the second picture in GOP8, can be decoded. For this purpose, the first picture of GOP8 currently being decoded is displayed. Encoded data from the hard disk must be read from the hard disk. Actually, it is necessary to read the packet header including the GOP header and the encoded data from the head of the pack header including the packet header from the hard disk 10. However, unless otherwise specified, the encoded data Is assumed to be a video stream, and the head of the pack header is G
The description will be made with the head of the GOP header in FIG.

Assuming that there is no loss of encoded data due to underflow or overflow in the video buffer 30 or the audio buffer 40, as shown in FIG.
P8 start address value of the A0, B (25) after the end of decoding of the picture, when the address value of the encoded data at the stop time of reading from the hard disk 10 at step 301 and A _1, (A ₁ -A ₀ ) becomes the following [Equation 1].

FIG. 9A shows a read signal from the hard disk 10 and FIG. 9B shows a read signal from the video buffer 30 on the same time axis. (C) shows the GOP FLAG, (d) shows the value of the transfer counter DC, and (e) shows the value of the frame counter FC.

(A ₁ −A ₀ ) = (accumulated value of video buffer) + (total amount of coded data from the first picture of the current GOP to the decoded picture) [Equation 1] Can be rewritten by the following [Equation 2].

(A ₁ −A ₀ ) = (accumulated value of video buffer) + {total amount of encoded data from I (26) picture to B (25) picture} (Equation 2)

The transfer counter DC shown in FIG. 1 is cleared to 0 when the GOP header is detected, and is incremented every time encoded data is transferred. FIG. 9 shows that the transfer has been performed six times when the decoding of the B (25) picture as the third picture is completed. Assuming that the value of the transfer counter DC represents the total amount of encoded data from I (26) picture to B (25) on average, [Equation 2] can be approximated by the following [Equation 3]. .

A ₀ = A ₁ − (accumulated value of video buffer + transfer counter DC × transfer unit α) [Equation 3]

If the video bit rate value and the display rate (see FIG. 2 (c)) in the sequence header stored in the header information storage unit 50 are used, [Equation 2] is also obtained by the following [Equation 4]. Can be approximated. A ₀ = A ₁ − (accumulated value of video buffer + frame counter FC × video bit rate / display rate) [Equation 4]

Then, in step 312 of FIG. 6, the start address A0 of GOP8 is calculated by [Equation 3] or [Equation 4]. Next, in step 316, the register FIRST is set to 0.
Then, the GOP counter GC is cleared to 0. At the same time, the time code value of the time code register TC is held in the register TCM, and the process proceeds to step 308.

Next, in step 308 of FIG. 6, the decoding operation of the video decoding unit 32 and the audio decoding unit 42 is stopped.
The encoded data stored in the video buffer 31 and the audio buffer 41 is cleared. Then step 3
At 09, the hard disk control unit 12 is instructed to read the encoded data from the GOP start address A0 calculated at step 312 previously. Hard disk controller 1
2 seeks the head 11 to the transfer source address A0 and reads the encoded data. The coded data is read out in the order of the trajectory 101b of the coded data shown in FIG. 3, and sent to the signal readout unit 13, the system separation unit 20, the video buffer 30, and the video header separation unit 31 as described above.
Then, the GOP header is separated by the video header separation unit 31 and sent to the header storage unit 50.

When detecting the GOP header, the controller 80 executes the GOP header subroutine processing of FIG. 8A. The process proceeds from step 350 to step 360 in FIG. 8 to determine the register MODE. Since MODE = 3 now, the process proceeds to step 361, and the GOP counter GC is cleared to 0. Next, at step 354, the transfer register DC is cleared to 0. In step 355, the register GOP FL
Set 1 to AG and exit the GOP header subroutine.

FIG. 7 is a block diagram of FIG.
5 is a flowchart showing details of the reverse reproduction operation of FIG.
In step 320 of FIG. 7, the register GOP FLAG is determined. Since GOP FLAG = 1 now, step 321 is executed.
Proceed to. In this step, the register GOP FLAG is set to 0
And the time code stored in the header information storage unit 50 is substituted into the register TC, and the routine proceeds to step 322.

Now that MODE = 3, the process proceeds to step 330, and further proceeds to step 331 to compare the register TCM with the register TC. This step will be described with reference to FIG. FIG. 10A shows GOP8.
5 shows the acquisition status of the time code based on the reverse reproduction command in F (25). The upper portion shows the acquisition status of the time code of GOP8, and the lower portion shows the acquisition status of the time code of GOP9. The upper part skips over the header of GOP8 based on the reverse reproduction command and
Of the encoded data is read from the part after
The situation where the time code of OP8 is obtained is shown. On the lower side, a situation is shown in which reading of encoded data starts after the header portion of GOP8 by skipping, and the time code of GOP9 is obtained without obtaining the time code of GOP8.

The transfer source address A0 calculated using [Equation 3] or [Equation 4] does not represent the true start address of GOP8 on the encoded data, but merely indicates the average position. . Transferred source A0 is a true GOP
If it is an address before the start address of No. 8, the time code selected in step 321 is the time code of GOP8. However, seek source address A0
Is the address after the start address of the true GOP8, the next GOP to be reproduced is GOP9, and the B (24) picture to be decoded next cannot be obtained.

In step 331 of FIG. 7, an algorithm for comparing the acquired time codes is provided, and TCM = T
It is compared with C or not, and if different, the process proceeds to step 332. Β which is an arbitrary number of bytes from the calculated transfer source address A0
The value obtained by subtracting only bytes is the new transfer source address A0 '
Is recalculated using [Equation 5], and step 30 in FIG.
Return to 6. New transfer source address A0 ′ = A0−β [Equation 5] Thereafter, the above steps are repeated until TCM = TC in step 331. If the time codes become the same, the process proceeds to step 323.

In step 323 of FIG.
The processing is repeated to the transfer subroutine of FIG. 4B until the MP and the frame counter FC are compared and become equal. Then, each time the encoded data is read, the transfer counter DC is counted up. I at the beginning of GOP8
(26) When the picture is decoded, the processing is shifted to the picture header subroutine and the frame counter FC
Counts up to FC = 1. Decrypted F
(26) is input to the first frame memory 61, and the output of the decoding output unit 70 is switched to the second frame memory 62, but the output of the video output unit 71 is still switched to the fourth frame memory 64. , The F (25) frame is still output to the video monitor 72.

Next, when the B (24) picture which is the second picture is input to the decoding unit 42, the processing is again shifted to the picture header subroutine shown in FIG. 8B, and the frame counter FC counts up. And FC = 2
become. The decoded F (24) is input to the third frame memory 63, and the output of the decoding output unit 70 is switched to the third frame memory 63 side.

Since the value of the frame counter FC = 2 is equal to the value of the register COMP, it is determined that the decoding has been performed up to a predetermined position, and the flow advances to step 325.
The output of the video output unit 71 is switched to the third frame memory 63 side. Then, the video data of the third frame memory 63 is output. At this time, F (24) is displayed after F (25) on the video monitor 72, so that the user can see as if reverse playback is being performed. Then, after the end of step 325, the process exits the reverse reproduction subroutine shown in FIGS. This means exit from the reverse reproduction subroutine 211 of FIG.

In the reverse reproduction operation (1) described above, that is, in the reproduction operation from F (25) to F (24), the m-th GOP is GOP8, and n = 3, that is, the third picture Is a case where the backward reproduction is performed during the decoding of .gamma .. Since (n-1) .gtoreq.2.
By decoding in the forward direction from the first picture of OP8, F (24) can be decoded following F (25).

FIG. 5 illustrates the reverse reproduction operation of GOP8 following the forward reproduction of GOP8 described above. FIG. 5A shows a reproduction trajectory, which is a forward reproduction trajectory 10.
A trajectory 101b accompanying the reverse reproduction is shown skipped based on the reverse reproduction command from 1a. FIGS. 5 (b) to 5 (t) show the state of each part accompanying this, and FIG.
Is the GOP FLAG, (c) is the GOP number, and (d)
Is the time code, (e) is the order of pictures to be decoded, (f) is the state of the frame memory 61, (g) is the state of the frame memory 62, and (h) is the state of the frame memory 6.
3, (i) shows the state of the frame memory 64,
(J) shows the state of the decoding output unit 70, and (k) shows the state of the input to the video output unit 71. Note that in FIG.
Denotes the decoding output unit 70 side, and H denotes the sub memory SM side.

FIG. 5 (l) shows the output of the video output unit 71,
(M) shows the state of the register FIRST, (n) shows the state of the register MODE, (o) shows the state of the frame counter FC, (p) shows the state of the GOP counter GC, and (q)
Indicates the state of the transfer counter DC, and (r) indicates the register DCM.
(S) shows the state of the time code register TC, and (t) shows the state of the register TCM.

To end the reverse reproduction, the process proceeds from step 212 to step 213 in FIG.
VERSE is cleared to 0, and the register FIRST is cleared to 0, and the process of the forward reproduction is returned. When the reverse reproduction is continued, the process returns to the reverse reproduction subroutine.

[Reverse Playback Operation (2): Playback from F (24) to F (23)] Further, reverse playback is continued, and F (2
The operation in the case where F (23) is reproduced from 4) will be described.
The mth GOP is GOP8, and its n = 2nd FOP
(23) is reproduced. In FIG. 6, steps 300 to 302 are the same as those described above, and a description thereof is omitted.
The video signal of 4) is transferred to the frame counter 64 and is displayed. . In step 303, 1 is subtracted from the frame counter FC and substituted into the register COMP. Now, COMP = 1.

Next, the process proceeds from step 304 to step 305, where the value of the register COMP is compared with 1. Step 305 is a step of determining whether or not to calculate the head address of the immediately preceding GOP. Since (n-1) = 1 and COMP = 1, the head address of the immediately preceding GOP is calculated. Judge to calculate the address. Next, the F (23) frame is displayed in reverse reproduction. This is the previous G
Since P (23) in OP7 needs to be decoded, the next transfer source address A0 must be the head address of the immediately preceding GOP7. Since COMP = 1 now, the process proceeds to step 314, where 2 is set in the register MODE, and the process proceeds to step 315.

Assuming that there is no loss of encoded data due to underflow or overflow in the video buffer 30 or the audio buffer 40, the start address value of the GOP 7 is set to A0, and after the decoding of the B (25) picture is completed, step 301 the address value of the encoded data at the stop time of reading from the hard disk 10 when the a ₁ at, can be represented by (a ₁ -A ₀₎ the following [equation 6].

(A ₁ −A ₀ ) = total amount of encoded data of the immediately preceding GOP + accumulated amount of video buffer + total amount of encoded data from the first picture of the current GOP to the decoded picture [Equation 6] ]

[Equation 6] can be rewritten into the following [Equation 7]. (A ₁ −A ₀ ) = total amount of encoded data of GOP7 + accumulated amount of video buffer + total amount of encoded data from I (26) picture to B (25) [Equation 7]

Each time a GOP header is detected, a register DCM has a transfer counter DC immediately before the end of the GOP.
Is held. Here, the value of the register DCM is the value held in step 353 in the previous forward reproduction locus 101a, and it can be assumed that this value indicates the average total amount of encoded data of GOP7. Similar to Equation 3, it can be approximated by the following [Equation 8].

A0 = A1− (accumulated value of video buffer) + (register DCM + transfer counter DC) × transfer unit α) [Equation 8]

Also, [Equation 8] can be approximated by the following [Equation 9], similarly to [Equation 4]. A0 = A1− (accumulated value of video buffer + (register FCM + frame counter FC) × video bit rate / display rate) [Equation 9] Then, in step 315, GOP7 is calculated using [Equation 8] or [Equation 9]. The start address A0 is calculated.

Next, step 316 and step 30 in FIG.
After step 7, the process proceeds to step 308, and further proceeds to step 309. The decoding operation of the video decoding unit 32 is stopped to clear the data in the video buffer 30, and the head 11 is sought to the transfer source address A0 to start reading the encoded data.

When the GOP header is detected again, FIG.
In the GOP header subroutine shown in FIG.
P FLAG is set to 1 and step 321 in FIG.
The step of storing the time code of the header information storage unit in the register TC is as described above. Step 32
In step S2, the register MODE is compared. Since MODE = 2, the process proceeds to step S340 via step S330.

Step 340 will be described with reference to FIG. The start address of GOP7 calculated using [Equation 8] or [Equation 9] does not represent the true start address of GOP7 on the encoded data, but merely indicates the average position. If the sought transfer source address A0 is an address before the true start address of GOP8, the time code obtained in step 340 is the time code of GOP7 as shown in the upper part of FIG. However, seek source address A
If 0 is an address after the start address of the true GOP7, the GOP to be reproduced next is GOP8 as shown in the lower part of FIG.
3) Pictures cannot be obtained.

At step 340, an algorithm for comparing the acquired time codes is provided, and it is determined whether TC> TCM.
If it is larger than M, the process proceeds to step 332, where a value obtained by subtracting an arbitrary number of bytes β from the calculated transfer source address A0 is recalculated using [Equation 5] as a new transfer source address A0 ′. Return to step 306.
If the obtained time code TC is smaller than the register TCM, the process proceeds to step 341 to calculate the difference between the value of the TCM register and the time code TC, and to store the value in the register M
Substitute for The calculated value M becomes the number of frames of GOP7 as it is. The decoding trajectory at this time draws 101c in FIG. 3 and FIG.

Since MODE = 2 at this time, the process proceeds from step 342 to step 344. In order to display the F (23) frame on the video monitor 72, after decoding all the pictures in GOP7, the first picture of GOP8, I
(26) The picture must be decoded. This I
(26) First, in step 34, to determine the picture
1 is added to the value of the register M calculated in step 1
Substitute for OMP.

When the GOP header is detected, the processing shifts to the GOP header subroutine of FIG. The process proceeds to step 362 only when the register MODE = 2, and the GOP
The counter GC is counted up. Register MODE
, The GOP counter GC is always cleared to 0.

B (22) which is the last picture of GOP7
Until the decoding of is completed, a processing loop is formed from step 345 to step 347, and returns from step 347 to step 345 via step 348. B (22)
At the time when the picture is decoded, the value of the frame counter FC is set to 12, and the value of the GOP counter GC is set to 1. Note that the decryption of P (23) has already been completed, and
(23) The frame has been input to the second frame memory 62.

When decoding of all pictures in GOP 7 is completed, the encoded data of GOP 8 is decoded next.
Since the GOP header is detected at the same time, the GOP counter is counted up at step 362 in the GOP header subroutine to set GC = 2. Then, the process proceeds from step 345 to step 346, and the value of the transfer counter DC is held in the register DCM. The transfer counter DC is G
Since it is cleared to 0 each time the OP header is detected,
The value of the register DCM obtained in step 346 is GOP7
, Approximately represents the total amount of encoded data.

When the register MODE is 2, G
Even if the OP header is detected, the frame counter FC is not cleared to 0. Therefore, the leading picture of GOP8, I
The frame counter FC when (26) is decoded counts up from 12 to 13. Then, the process proceeds from step 347 to step 325 to switch the output of the video output unit 71 from the fourth frame memory to the decoding output side. When decoding of the I (26) picture is started,
Since the output of the decoding output unit 71 is switched to the third frame memory 63, F (2
3) The frame is output from the video output unit 71, and F (23) is displayed after F (24) on the video monitor 72, so that the user can see as if performing reverse playback.

[Reverse Playback Operation (3): Playback from F (23) to F (22)] If the reverse playback is to be continued further, the process returns to the reverse playback subroutine again. Since the F (23) frame is currently displayed on the video monitor 72, the next frame to be displayed is F (22). F (22) is the n = 1st picture of the mth GOP8, and (n-1)
= Is the case. Since F (22) only needs to decode the twelfth (final) picture in GOP7, head 1
The transfer source address A0 for seeking 1 is determined by the previous step 3.
The head address of GOP7 calculated in 15 may be used as it is. The trajectory of the decoding is the trajectory 101d of FIGS.
Obey.

The contents up to step 302 in FIG. 6 have already been described, and the contents of F (23) in the frame memory 63 are copied to the frame memory 64. Current frame counter F
Since the value of C is 13, the register COM is
Set the value of P to 12. This compares the twelfth picture. After step 304, step 30
Proceed to 6 to clear the register MODE to 0. In step 308, the decoding operation of the video decoding unit is stopped, and the video buffer 31 is cleared. And step 3
09, the transfer source address A0 which is the head address of the GOP
Causes the head 11 to seek.

When the encoded data is read from the hard disk 10 and the GOP header is detected, the processing of the GOP header subroutine is executed. When the process is completed, the process proceeds from step 320 to step 323, and the process of the transfer subroutine is repeated until the frame counter FC becomes equal to the register COMP. Since the register COMP is 12, when the B (22) picture which is the last picture of GOP7 is decoded, steps 323 to 3 are executed.
Go to 25. At this time, GO is stored in the third frame memory.
Since F (22) frame data obtained by decoding the last B (22) in P7 is stored, the F (22) frame is displayed on the video monitor 72 after the F (23) frame.

[Reverse playback operation 4: F (22) to F
(12) Reproduction] When the reverse reproduction is to be continued, the process is again shifted to the subroutine of the reverse reproduction to draw the encoding trajectory 101f of FIG. 3 and FIG.
(21) Decode from picture to B (12) picture. In the reproduction of each picture, the F (1
Reverse playback up to 2) in picture units can be performed continuously. In this case, the m-th GOP reproduced in the backward direction is GOP7, and the reverse reproduction of any picture is (n-1).
Since decoding is performed under the condition of ≧ 2, decoding from the first picture of GOP7 enables reverse reproduction in picture units.

[Reverse playback operation 5: F (12) to F
(11) Reproduction] Next, the reverse reproduction in picture units proceeds continuously, and B (12) which is the second picture in GOP7
A case will be described in which a transition is made from the reverse reproduction state of the picture to reproduction of B (11). First, in the reproduction state of B (12), the decoding trajectory is 101f in FIG. When the B (12) picture is decoded, the frame displayed on the video monitor 72 is the F (12) frame, the value of the frame counter FC is 2, and the value of the register TCM is GOP.
The time code of 7 and the value of the register MODE are 0.
Further, the register DCM stores G in the preceding decoding trajectory 101c.
At step 345 in the OP header subroutine,
When the GOP counter GC becomes equal to 2, the value of the transfer counter FC is held. The value of the retained DCM is
Since it has not been updated since then, its value indicates an approximate value of the total amount of encoded data of GOP7.

The following reverse reproduction of F (11) will be described with reference to FIG.
When the processing shifts to the reverse reproduction subroutine shown in FIG.
At step 303, the value of the register COMP becomes 1.
The fact that the value of the register COMP is 1 means that the value of the register MODE is set to 2 in step 306,
The process proceeds to step 315 where the transfer source address A0 is calculated as the head address of the immediately preceding GOP6.

Also in the previous decoding trajectory 101b, the head address of the immediately preceding GOP 7 is calculated in step 315 using [Equation 8] or [Equation 9]. In this case, since the normal reproduction from GOP6 to GOP8 was immediately followed by the reverse reproduction, the value of DCM in [Equation 8] or the value of FCM in [Equation 9] was changed during normal forward reproduction. G
It was obtained in step 353 of the OP header subroutine processing. However, in the case of the decoding trajectory 101f, the information of GOP6 acquired at the time of normal reproduction has already been lost at the time of decoding GOP7, so that the information cannot be acquired. This applies not only to GOP6 but also to reverse reproduction of GOP5 and GOP4 before that. Even in this case, the present embodiment does not cause any problem.

[0102] Coding at a fixed rate and each GO
If the number of pictures of P is equal, the total amount of encoded data of each GOP will be substantially equal. Therefore, there is no problem if the value of the register DCM, which is the total amount of the encoded data of GOP7, is used as the parameter for calculating the start address of GOP6. Since the value of the register DCM or the register FCM is rewritten only when the decoding of all the pictures in the GOP is completed in the case of the register MODE = 2, the expression 8 or the expression 9 performed in step 315 of the decoding trajectory 101f is used. Is used, the value of the register DCM or the register FCM, which is the total amount of the encoded data of the GOP 7, is used as it is.

The head address A0 of the calculated GOP6
Is before the start address of the true GOP,
6 can be decoded correctly, and the encoded trajectory 101g of FIG. 3 can be drawn. On the other hand, even if the calculated transfer source address A0 of GOP6 is after the head address of the true GOP, it is recalculated in step 332, so that no problem occurs in this case. Also, in the coding trajectory 101g, the register DCM or the register FCM holds the value of the transfer counter DC or the frame counter FC after B (10), which is the last picture of GOP6, is decoded. There is no inconvenience when calculating the start address of GOP5. In this way, by repeatedly performing the above-described reverse reproduction algorithm, it is possible to perform reverse reproduction in units of pictures. By using such an algorithm, the configuration of reverse reproduction can be simplified, and a good encoding device can be obtained.

The case where encoding is performed at a fixed rate according to the MPEG standard has been described above.
According to the EG standard, there is a case where the number of pictures changes in a variable code rate or a GOP unit (hereinafter, referred to as an active GOP). The total amount of encoded data may fluctuate extremely in GOP units. As shown in FIG. 10 (c), if GO
For the total amount of P7 encoded data,
Is small, and suppose that GOP4 to GO
When the total amount of the encoded data of P6 is substantially equal, GOP
6 may seek to the beginning address of GOP4. Even in this case, the present embodiment does not cause any problem.

Such a case is shown in an encoding trajectory 101h of FIG. When the encoded data is read from the transfer source address A0 in the state of the register MODE = 2,
The time code of GOP4 is detected.
The difference between the time codes of OP4 and GOP7 is calculated and assigned to the register M. In this case, GOP4, GOP5, G
The process proceeds so that OP6 is collectively handled as one GOP block. It should be noted that FIGS.
(F) is a GOP counter GC corresponding to FIG.
The state of the transfer counter DC and the register DCM is shown.

Further, as shown in FIG.
The value of the GOP counter GC of P4 is 1, the GOP of GOP4
The value of the counter GC is 2, the GOP counter GC of GOP4
Is 3, and the value of the GOP counter GC is counted up every time a GOP header is detected. in this case,
The value of the register DCM held in step 346 is 1
This is not the total amount of encoded data of all the blocks, but the total amount of encoded data of GOP4 alone, which is the first GOP of the GOP block. Even in the case of a variable code rate or an active GOP, the total amount of encoded data of adjacent GOPs is often almost equal. Therefore, rather than calculating the start address of the immediately preceding GOP using the total amount of coded data of one block, the calculation using the total amount of coded data of the first GOP of one block is more converse. The algorithm for directional reproduction can be performed at high speed.

The above embodiment has described the case where the decoded picture at the time of transition from the normal reproduction to the backward reproduction is the second picture or later in the GOP. Next, a case in which the transition from the first picture of the GOP to the reverse playback is performed will be described.
A case will be described as an example where the normal reproduction is completed up to I (26) of GOP8, and the process shifts to the reverse reproduction. The frame currently displayed is the F (23) frame. Therefore, the next frame to be displayed needs to decode B (22) which is the last picture of GOP7.

In this case, the process shifts to the reverse reproduction algorithm with the register FIRST = 1 and the frame counter FC = 1. First, the register COMP becomes 0 in the operation of step 303. Then, the process proceeds from step 304 to step 317 to set the register MODE to 1. Then, through the above-mentioned algorithm, step 32
2 to step 343. Since the last picture of GOP7 is decoded, the register COMP
Is set to the value of M, in this case, 12. Then, the process proceeds to a step 347, wherein a transfer subroutine is executed until B (22) is decoded. If B (22) has been decoded, the process proceeds to step 325, and the subsequent algorithm is as described above. With such a configuration, it is possible to realize reverse reproduction from all picture positions by simple means.

In this embodiment, the difference between the time codes is calculated as the number of frames in step 341, but this is for a non-drop frame. Here, a case of a drop frame will be described.

The drop frame has a display frame of 2
This means rounding up 9.97 Hz time code to 30 Hz time code. This means that the time code values of the first and second frames whose time code values are other than 0, 10, 20, 30, 40, and 50 minutes (for example, 11 minutes and 59 minutes) are discarded. It is something that can be done. That is, "10:59" is not "11:00" but "11:02".

Since the drop is in the head flag of the time code of the GOP header, the controller 80 can easily detect the drop. If the controller 80 detects that the frame is a drop frame, it confirms the existence of the above-mentioned time code value for rounding up between the time codes TC and TCM, and if so, the time code of the first and second frames. A similar effect can be obtained by truncating the value.

In the above embodiment, the case of coded video data has been described. However, a case of a program stream in which coded video data and coded audio data are multiplexed may be used. In this case, the transfer source address A0 may be calculated in consideration of the storage amount of the audio buffer 42 in addition to the storage amount of the video buffer 32, and the same effect can be obtained.

[0113]

As described above, in the method of reproducing encoded data according to the present invention, backward reproduction is instructed while decoding the n-th picture of the m-th picture structure group, and the (n-1) -th picture is reproduced. When decoding (n-1) ≧ 2, the (n−1) th picture is decoded by decoding from the first picture of the mth picture structure group, and (n−1) = 1 or 0, then (m-
Since the (n-1) th picture is decoded by decoding from the first picture of the 1) th picture structure group, for example, the first type of picture is an I picture, and the second type of picture is a B picture. Alternatively, even in the case of a P picture, it is possible to perform reverse reproduction in picture units.

Further, in the encoded data reproducing apparatus of the present invention, a picture structure group counting means for counting picture structure groups, a picture counting means for counting pictures in each picture structure group, and a decoding direction is either forward or backward. Information holding means for holding such information, and (n-
1) Since the data read start position control means for calculating the read start position of the encoded data from the recording medium in decoding the first picture is provided, when (n-1) ≧ 2, the m-th picture structure Decode the (n-1) th picture by decoding from the first picture in the group, and when (n-1) = 1 or 0,
Since the (n-1) th picture is decoded by decoding from the first picture of the (m-1) th picture structure group, even if the first type of picture is an I picture and the second type of picture is Is a B-picture or a P-picture, it is possible to realize reverse playback in picture units.

In the encoded data reproducing apparatus according to the present invention, when (n-1) ≥2, the decoding of the (n-1) th picture of the m-th picture structure group is followed by the (n-
When decoding the (2) th picture, the (n-2) th picture is decoded using the address value calculated by the read start position control means in decoding the (n-1) th picture. Therefore, even if the first type of picture is an I picture and the second type of picture is a B picture or a P picture, it is possible to realize reverse reproduction in picture units by a simpler apparatus.

Further, according to the encoded data reproducing apparatus of the present invention, the data reading start position control means uses the transfer counter, and the data reading start position control means uses the value of the transfer counter at the time of forward decoding before backward decoding to perform the m-th picture group. In controlling the reading start position corresponding to the first picture of
More simply, even if the first type of picture is an I picture and the second type of picture is a B picture or a P picture, it is possible to realize reverse reproduction in picture units.

Further, according to the encoded data reproducing apparatus of the present invention, there are provided a main memory means having three frame memories and a sub memory means having at least one frame memory. When reverse playback is commanded, the n-th decoded data is stored and displayed in the sub-memory means, and the (n-1) -th picture is decoded and displayed using the main memory means. Using a smaller number of frame memories, it is easier to use a picture of the first type if the picture is an I picture,
Even if the type of picture is a B picture or a P picture, reverse playback in picture units can be realized.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of the present invention.

FIG. 2 is a schematic diagram showing the configuration of encoded data according to the MPEG standard.

FIG. 3 is a time chart showing an operation at the time of forward reproduction according to the first embodiment of the present invention.

FIG. 4 is a flowchart showing the operation of the first embodiment of the present invention.

FIG. 5 is a time chart showing forward and reverse reproduction operations according to the first embodiment of the present invention;

FIG. 6 is a flowchart showing a reverse reproduction operation according to the first embodiment of the present invention.

FIG. 7 is a flowchart showing a reverse reproduction operation according to the first embodiment of the present invention.

FIG. 8 is a flowchart of a GOP header subroutine and a picture header subroutine according to the first embodiment of the present invention.

FIG. 9 is a time chart showing a read operation from a hard disk and a video buffer according to the first embodiment of the present invention.

FIG. 10 is a time chart showing a time code acquisition operation according to the first embodiment of the present invention.

FIG. 11 is a diagram showing a picture configuration for explaining a conventional configuration.

[Explanation of symbols]

Reference Signs List 10 hard disk 11 head 12 hard disk control unit 13 signal readout unit 20 system separation unit 30 video buffer 31 video header separation unit 32 video decoding unit 40 audio buffer 41 audio header separation unit 42 audio decoding unit 50 header information storage unit 60 frame memory control unit 61 first frame memory 62 second frame memory 63 third frame memory 64 fourth frame memory 70 decoding output unit 71 video output unit 72 video monitor 80 controller 80A register or counter group MM main memory SM sub memory.

Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat II (reference) H04N 7/24 F term (reference) 5C053 FA23 GB04 GB06 GB08 GB37 HA25 HA33 JA07 JA22 JA24 KA04 KA24 LA06 LA11 5C059 KK13 MA00 PP05 PP06 PP07 RB09 RB14 RC02 RC04 RC26 SS12 SS18 UA05 UA32 UA35 UA36 UA38 5D044 AB07 BC01 CC04 FG10 FG23 FG30 GK08

Claims (5)

[Claims] 1. A picture type group recorded on a recording medium and including a plurality of picture structure groups, wherein each of the picture structure groups is a first type of picture that can be decoded in the picture structure group;
This is a method of reproducing encoded data including a picture of the second type that can be decoded from the picture structure group and another picture structure group that follows the m-th picture (where m is a natural number of 2 or more). ), The decoding in the direction opposite to the recording direction is instructed during decoding of the n-th picture (n is a natural number of 3 or more), and the (n−1) th decoding of the m-th picture structure group is performed. Is a method for decoding the picture of the m-th picture structure group. When (n-1) ≧ 2, the decoding of the m-th picture structure group from the first picture in the same forward direction as the recording direction is performed. Decodes the (n-1) th picture of the picture structure group of
-1) = 1 or 0, the decoding is performed in the forward direction from the first picture of the (m-1) -th picture structure group, whereby (n-
1) A method for reproducing encoded data, characterized by decoding a picture. 2. A picture type group recorded on a recording medium and including a plurality of picture structure groups, each of the picture structure groups being a first type of picture that can be decoded in the picture structure group;
An apparatus for playing back encoded data including a picture of a second type that follows and that can be decoded from the picture structure group and another picture structure group;
While decoding the n-th (n is a natural number of 3 or more) picture in the m-th (m is a natural number of 2 or more) picture structure group,
The decoding in the direction opposite to the recording direction is instructed to decode the (n-1) th picture of the m-th picture structure group, wherein the recording medium on which the encoded data is recorded and the picture structure group are counted. Picture structure group counting means, picture counting means for counting the pictures in each picture structure group, information holding means for holding information as to whether the decoding direction is the same as the recording direction or the reverse direction, and A data read position control means for calculating a read start position of coded data from the recording medium when decoding the (n-1) th picture; and when (n-1) ≧ 2, the data read position By decoding in the forward direction from the first picture of the m-th picture structure group based on the operation of the control means, Decode the (n-1) th picture of the picture structure group, and when (n-1) = 1 or 0, decode in the forward direction from the first picture of the (m-1) th picture structure group (N)
-1) An encoded data reproducing apparatus for decoding a first picture. 3. When (n−1) ≧ 2, following the decoding of the (n−1) th picture of the mth picture structure group, the (n−2) th picture is decoded. In this case, in decoding the (n-1) th picture, reading of data from the recording medium is started using the same address calculated by the reading position control means, and the (n-2) th picture is 3. The apparatus for reproducing encoded data according to claim 2, which is decoded. 4. A transfer counting means for counting the number of times a predetermined amount of data is read from the recording medium,
The data read position control means controls a read start position corresponding to the first picture of the m-th picture structure group by using a value of the transfer counter means at the time of the forward decoding before the backward decoding. An apparatus for reproducing encoded data according to claim 2. 5. A main memory having three frame memories and a sub-memory having at least one frame memory, wherein said backward decoding is started at an n-th picture of an m-th picture structure group. The decoded data of the n-th picture in the m-th picture structure group is held and displayed in the frame memory of the sub-memory means, and the (n-1) -th picture is decoded by using the main memory means. 3. The encoded data reproducing apparatus according to claim 2, wherein the encoded data is displayed subsequent to the n-th picture.