JP2000078523A - Compressed stream decoding method and compensation stream decoder - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid the occurrence of a decoding error in the case of special reproduction by decreasing a size of a retrieval table for decoding a B picture. SOLUTION: A stream structure analysis circuit 8 generates a stream structural table 7 in the case of usual reproduction. The stream structural table 7 includes decoding sequence as counts of a decoding sequence counter, and the stream structure analysis circuit 8 generates automatically the decoding sequence based on frame addresses in a bit stream storage memory 3 arranged in the decoding sequence. Furthermore, the storage sequence of picture information such as the decoding sequence in the stream structural table 7 is selected to be image display sequence. The display sequence is realized by allowing the stream structure analysis circuit 8 to write directly picture information in the case of a B picture and to write picture information while holding it up to a succeeding core picture address in the case of a core picture into the stream structural table 7. In the case of reproduction in a reverse direction, a read control circuit 4 references the stream structural table 7 in reverse sequence, allows a decoder 5 to read a require frame stream from the bit stream storage memory 3 and to decode it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compressed stream decoding method and a compressed stream decoding apparatus for decoding a compressed stream encoded by an inter-frame predictive encoding method such as the MPEG method, and more particularly, to a method for decoding a compressed stream. The present invention relates to a decoding technique in trick play such as playback.

[0002]

2. Description of the Related Art As a conventional technique of this kind, for example, a "video signal decoding method and a video signal decoding apparatus" described in Japanese Patent Application Laid-Open No. 10-13793 is known. FIG.
FIG. 1 is a block diagram of Embodiment 1 of the video signal decoding device, which is a copy of FIG. 1 of the same publication (however, reference numbers are changed).

In the present video signal decoding apparatus, an optical disk 101 records a bit string obtained by compressing and encoding a video and audio signal according to the MPEG system, and an optical disk reading circuit 102 reads the optical disk 1, performs deinterleaving and error correction. The subsequent bit string 121 is output.
Reference numeral 103 denotes a bit string storage memory which stores a bit string 121 output from the optical disk reading circuit 102 and which receives an address signal 14
The bit string 121 is output according to 1. Reference numeral 105 denotes a search table, each of which is stored in the bit string storage memory 103.
The address of the picture is stored. Reference numeral 106 denotes a search table creation circuit, which includes an address signal 141 and a B picture detection signal 172.
The search table 105 is created on the basis of. A picture header detection circuit 107 determines the picture type of the bit string of the input frame, and sends an encoding control signal 171 to the decoding circuit 108 and B
The picture detection signal 172 is output. Reference numeral 108 denotes a decoding circuit which decodes the input bit string 121 to obtain a reproduced image and outputs a reproduced signal 181. 191
Reference numerals 193 indicate frame memories for recording reproduced pictures of I pictures and P pictures as reference pictures.

[0004] The optical disk 101 of the video signal decoding apparatus configured as described above records a video signal that has been compression-encoded according to the ISO MPEG video standard (hereinafter referred to as the MPEG system). The MPEG method is a highly efficient compression coding method based on inter-frame prediction coding.
By switching the prediction method for each of a plurality of frames, high compression efficiency and reproduction from the middle of the sequence can be realized.

FIG. 8 is a diagram showing a plurality of temporally continuous image frames. A prediction method of the MPEG system will be described with reference to FIG. In the figure, the numbers given below each frame indicate the serial number of each frame, and indicate that time advances in the direction of increasing the serial number. For example,
The frame with the serial number 11 is the next frame after the frame with the serial number 10.

The alphabets given below each frame indicate the prediction method of each frame. The frame denoted by I is called an I picture, and the intra-frame code which can be encoded only by the information in the frame. Image. The frame denoted by P is called a P picture,
This is a unidirectional predictive encoded image in which encoding is performed using a picture or a P picture as a reference image. For example, serial number 1
The P picture No. 3 is predictively coded from one direction using the P picture of the serial number 10 as a reference picture. The frame denoted by B is a B-picture, which is a feature of the MPEG system, and is a bidirectionally predicted coded image in which encoding is performed using the preceding and succeeding frames as reference images. For example, a B picture with a serial number 12 is predictively coded from both directions using P pictures with a serial number 10 and a serial number 13 as reference images.

In the MPEG system, an aggregate of a plurality of frames including one I picture is called a GOP (group of pictures). For example, in FIG. 8, 15 frames from the B picture with the serial number 2 to the P picture with the serial number 16 are one GOP unit, and the range indicated by the double-headed line labeled GOP (n) is 1 GOPs. Here, n is a serial number of the GOP given for the explanation. In the MPEG system, the P-picture and B-picture frames are predictively coded based on the data of the unidirectional and bidirectional frames, so that complete information is not obtained with only one frame. Therefore, for example, decoding and reproduction of a target image from the middle can be performed by randomly accessing a GOP unit in which data of a plurality of frames are collected. At this time, GOP
Contains one frame of an I-picture which is being coded using information only in the frame, so that decoding and reproduction starts from the I-picture.

FIG. 9 shows a bit string obtained by encoding each frame of FIG. As described above, the order of each frame is an order convenient for the encoding process and the decoding process, and thus differs from the order of the temporally continuous frames shown in FIG. For example, 4I indicates an I picture of a serial number 4 frame, 2B indicates a B picture of a serial number 2 frame, and 7P indicates a P picture of a serial number 7 frame.

FIG. 10 shows a GOP (n +) read from the optical disk 101 by the optical disk reading circuit 2.
It is a figure which shows the syntax of the bit string of 1). For example, from the bit string of 210a, 211a, and 212a, the frame 22P becomes
b, 211b and 212b. Here, 210a and 210b are picture start codes used only at the head of the picture, and are represented by 32 bits. 211a and 211b are temporal references, and the display order of each picture in the GOP is 10b.
It is represented by it. 212a and 212b are picture coding types, and the type of picture is represented by 3 bits. 211a indicates a P picture, and 212b
Indicates a B picture.

Returning to FIG. 7, the operation of the video signal decoding apparatus during forward reproduction will be described. The optical disk reading circuit 102 reads a signal from the optical disk 101 and outputs a bit string 121 in the order of GOP serial numbers. The output bit string 121 is stored in the bit string storage memory 1.
03, the bit string 121 is read out in the order of writing and input to the decoding circuit 108.
The decoding circuit 108 sequentially decodes the input bit sequence to obtain a reproduced output 181.

Next, the operation of the video signal decoding apparatus during reverse reproduction will be described, for example, in the case of reproducing in the reverse direction from a frame of GOP (n + 1). The optical disk reading circuit 102 reads the bit sequence of GOP (n + 1) from the optical disk 101 in which the bit sequence is stored. The header of such a bit string includes a picture start code, a temporal reference indicating the display order of each picture in the GOP, and a picture reference.
Consist of type.

GOP read from optical disk 101
The bit string of (n + 1) is stored in the bit string storage memory 103.
And then read out and input to the picture header detection circuit 107 and the decoding circuit 108. The order of this input is the same as the order stored in the bit string storage memory 103. The picture header detection circuit 107 detects the picture header of the bit string of each input picture and determines the type of coding of each picture based on the picture type. If the picture type is an I picture or a P picture, the decoding control signal 171
Thus, the decoding circuit 108 is instructed to perform a decoding operation, and the decoding circuit 108 performs decoding in the order of input. If the picture type is a B picture, the decoding control signal 171 instructs the decoding circuit 108 not to perform the decoding operation, and the decoding circuit 108 does not perform the B picture decoding operation.

The decoded I picture and P picture are
Since all of the bit strings of GOP (n + 1) are read out from the bit string storage memory 103, the frame memories 191 to 193 store the latest GOP (n + 1) in the GOP (n + 1). 3
A reproduced image of one core picture (I picture or P picture) remains, and the final core picture is
Output signal 181.

At the same time as the decoding operation of the I picture and the P picture as described above, the picture header detection circuit 107
The GOP (n +) stored in the bit string storage memory 103
From the bit string of 1), a B picture of GOP (n + 1) is detected and output to the lookup table creation circuit 106 as a B picture detection signal 172. The search table creation circuit 106 determines the bit string storage memory 103 from the currently output address signal 141 and the input B picture detection signal 172.
Since the storage address of the B-picture in (1) is known, the information of the B-picture address is output to the search table 105.

In the search table 105, the starting address of the B picture and the number of words in the bit string of the B picture are entered. In this publication, instead of this, the packet number and the temporal reference are entered. , Search Table 1
Another embodiment in which the size of the image 05 is reduced is also described.

On the other hand, the decoding operation of a B picture requires the preceding and succeeding core pictures as reference images. Since these are already present in the frame memories 192 and 193, the bit sequence of the B picture is stored in a bit sequence storage memory. 103
, And decoded by the decoding circuit 108 to obtain a reproduced picture of a B picture. At this time, since the location where the bit sequence of the B picture is recorded in the bit sequence storage memory 103 is described in the search table 105, the read control circuit 104 refers to the search table 105 to read the bit sequence of the B picture. Is output to the bit string storage memory 103. According to the address signal 141, the bit string storage memory 103 reads the bit string of the B picture, and the read bit string of the B picture is decoded by the decoding circuit 108 to obtain a reproduced image. The reproduced image of the B picture is recorded once in the frame memory 191 and then reproduced by the decoding device.
It is output as 81.

Next, the operation at the time of reverse reproduction will be described with reference to FIG. During reverse playback, the frame 30B is the next playback image after the frame 31P. The operation of the video signal decoding apparatus when a reproduced image of the frame 30B is obtained by reverse reproduction will be described. Since the frame 30B is a B picture, a decoded image of the frame 28P and the frame 31P is required as a reference image for decoding. These are already in the frame memory 19
2, 193, the bit string of the frame 30B is read from the bit string storage memory 103 and decoded by the decoding circuit 108 to obtain a reproduced image of the frame 30B. At this time, since the location where the bit string of the frame 30B is recorded in the bit string storage memory 103 is described in the search table 105, the read control circuit 1
04 outputs an address signal 141 for reading a bit string of the frame 30B to the bit string storage memory 103 with reference to the search table 105. This address signal 141
, The bit string storage memory 103 stores the frame 30B
, And the read bit string of the frame 30B is decoded by the decoding circuit 108 to obtain a reproduced image. The reproduced image of the frame 30B is recorded once in the frame memory 191 and then output as the reproduced output 181 of the decoding device. This situation is shown in (3) of FIG.

At the time of reverse reproduction, the frame 29B is the reproduction image next to the frame 30B. Since the frame 29B is a B picture, similarly to the decoding operation of the frame 30B, the frame 29B is decoded using the reproduced images of the frames 28P and 31P already existing in the frame memories 92 and 93 as reference images. To obtain a playback image. This situation is shown in (4) of FIG.

At the time of reverse reproduction, a frame 28P becomes a reproduction image next to the frame 29B. The frame 28P is a P picture, and has already been stored in the frame memory 92P.
Is output. At this time, although there is no particular need for decoding processing, frames 27B and 26B, which will be described later, which are the next reproduced images are B pictures, and reproduced images of frames 28P and 25P are required as reference images. However, since the reproduced image of the frame 25P does not exist in the frame memory,
5P decoding is performed simultaneously.

In order to obtain a reproduced image of the frame 25P, it is necessary to perform the decoding operation again from the beginning of GOP (n + 1). However, the reproduced image of the frame 28P already exists in the frame memory 92, and Since the reproduced image of the frame 31P, which is the P picture after the frame 28P, has already been output, the frames 19I, 22
Only the bit strings of P and frame 25P need to be read from the bit string storage memory 103. The read bit strings of the frame 19I, the frame 22P, and the frame 25P are decoded by the decoding circuit 108 and recorded in the frame memory. At this time, the frame memories 191, 193
Since the reproduced images of the frames 29B and 31P which have been already output and are unnecessary,
9B and the reproduction image of the frame 31P are overwritten, and the reproduction images of the latest reproduction images of the frames 22P and 25P are recorded in the frame memories 191 and 193. This situation is shown in FIG. 11 (4) and FIG. 11 (5).

At the time of reverse reproduction, the reproduction image following the frame 28P is the frames 27B and 26.
B. Since the frames 27B and 26B are B pictures, the above-described frames 30B and 2
9B, the frame memory 19 has already been decoded.
The frame 27B and the frame 2 are used as reference images with the reproduced images of the 28P and the frame 25P existing at 2,2193.
6B is obtained. This situation is shown in (6) of FIG. 11 and (7) of FIG.

Thereafter, until the reproduction output 181 of the reproduced image of the frame 19I is obtained, the operation of the main part of the video signal decoding apparatus according to the first embodiment at the time of reverse reproduction is performed as described above.

The decoding of the core picture and the B picture as described above is repeated in reverse order from the last core picture of the GOP (n + 1) to the first picture, thereby completing the reverse reproduction of the GOP (n + 1). . If this procedure is continued with GOPn, GOP (n-1)..., Desired reverse reproduction can be performed.

[0024]

However, in the above-described conventional video signal decoding technique, a search table for decoding a B picture is used. According to the first embodiment in which the number of words in the bit string of the picture is entered, there is a problem that the size of the search table increases.

In order to solve this problem, according to the second embodiment in which the B-picture packet number and the temporal reference are entered in the search table, when a stream is recorded on the optical disc or when the optical disc is At the time of reading, if the temporal reference is missing or misread, there is a problem that the order of reverse reproduction is out of order. This occurs when an incorrect display order is recorded on the temporal reference during the manufacturing process of the optical disk, or when the surface of the optical disk is damaged and the temporal reference cannot be normally reproduced.

Therefore, an object of the present invention is to provide a compressed stream decoding method capable of performing error-free special reproduction such as reverse reproduction even though the size of a retrieval table (referred to as a stream structure table in the present invention) is small. And a compressed stream decoding device.

Another object of the present invention is to provide a compressed stream decoding method and a compressed stream decoding apparatus capable of quickly performing trick play such as reverse play.

[0028]

Accordingly, a first compressed stream decoding method according to the present invention is a compressed stream decoding method for decoding a compressed stream encoded by an inter-frame predictive encoding method. At the time of normal reproduction, for a group of frames constituting the compressed stream, information including a decoding order and an encoding type is stored in a display order determined by the decoding order and the encoding type,
At the time of trick play, decoding is performed by referring to the decoding order in the display order or in the reverse order, and skipping timely according to the encoding type.

A second compressed stream decoding method according to the present invention is a compressed stream decoding method for decoding a compressed stream encoded by an inter-frame predictive encoding method, wherein a compressed stream is recorded from a medium on which the compressed stream is recorded. Reading a group of frames, storing the read group of frames in a bit string storage memory, reading a frame from the bit string storage memory, and selecting a first one of the read frames. A procedure of decoding only the frame of the encoding type, a procedure of storing a predetermined frame among the decoded frames in the frame memory, and a procedure of decoding the frame of the second encoding type among the frames read from the bit string storage memory. Decoding a frame only with reference to the frame memory, and, during normal reproduction, from the bit string storage memory For the extracted frame, a procedure for storing information including a decoding order and an encoding type in a stream structure table in a display order determined by the decoding order and the encoding type, and at the time of trick play, A step of controlling the reading of the frame by referring to the decoding order in the display order of the stream structure table or in the reverse order, and a step of skipping decoding in a timely manner according to the encoding type, I do.

A third compressed stream decoding method according to the present invention is a compressed stream decoding method for decoding a compressed stream encoded by the MPEG system, wherein a continuous GO stream is recorded from a recording medium on which the compressed stream is recorded.
A procedure of reading a frame in VOBU units having a P configuration, a procedure of storing the read frame in VOBU units in a bit string storage memory, a procedure of reading a frame from the bit string storage memory, A step of decoding only the frame of the core picture, a step of storing the latest three frames among the decoded frames in the frame memory, and a step of storing only the frame of the B picture among the frames read from the bit string storage memory. A procedure of decoding with reference to a frame memory, and displaying information including a decoding order, a picture type, and a GOP number for a frame read from the bit string storage memory during normal reproduction, the information being determined by the decoding order and the picture type. Stored in the stream structure table in order. Further, the display sequence of the stream structure table, or, in reverse order to control the reading of the frame by referring to the decoding order, and the step of skipping the decoding timely according to the encoding type, I do.

Further, in a preferred embodiment of the compressed stream decoding method according to the present invention, if the frame output from the bit string storage memory is a core picture, the display order is reserved until a frame output of the next core picture. Then, the information is written in the stream structure table, and if the frame output from the bit string storage memory is a B picture, the information is immediately written in the stream structure table.

Further, in a preferred embodiment of the compressed stream decoding method according to the present invention, the information stored in the stream configuration table includes a frame of another GOP when decoding a B picture included in the GOP. It is characterized by including an open / close flag indicating whether to refer or not.

Further, a preferred embodiment of the compressed stream decoding method according to the present invention is characterized in that a frame is read in GOP units instead of VOBU units.

Further, in a preferred embodiment of the compressed stream decoding method according to the present invention, when the trick play is reverse playback, the stream structure table is read in the reverse order of storage order.

Further, in a preferred embodiment of the compressed stream decoding method of the present invention, when the trick play is skip playback, the stream structure table is sequentially read only once for each skip. .

A first compressed stream decoding apparatus according to the present invention is a compressed stream decoding apparatus for decoding a compressed stream encoded by an inter-frame predictive coding method, wherein the recording medium recording the compressed stream is When,
Reading means for reading a group of frames from the recording medium, bit string storage means for storing the read group of frames, read control means for controlling the reading means and bit string storage means, and the bit string storage means Decoding means for decoding a frame read from a memory, and frame memory means for storing a predetermined frame of a first encoding type among the decoded frames and referred to during the decoding of a second encoding type And a stream structure table for storing information including a decoding order and an encoding type in a display order determined by the decoding order and the encoding type for a frame read from the bit string storage unit during normal reproduction. , A stream structure analyzing means for controlling the storage, and at the time of trick play, the read control means,
The stream structure table is displayed in the display order, or the reading control is performed with reference to the decoding order in the reverse order, and the decoding unit skips decoding in a timely manner according to the encoding type in the stream structure. Features.

A second compressed stream decoding apparatus according to the present invention is a compressed stream decoding apparatus for decoding a compressed stream encoded by the MPEG system, wherein a recording medium for recording the compressed stream, A data reading circuit for reading a frame from a medium in units of VOBUs having a continuous GOP structure, and a read VOBU;
A bit string storage memory that stores a unit frame; a read control circuit that controls the data read circuit and the bit string storage memory; a decoder that decodes a frame read from the bit string storage memory; The decoding order, picture type and GOP of the frame memory storing the latest three frames of the core picture and referred to during decoding of the B type frame and the frame read from the bit string storage memory during normal reproduction are stored. A stream structure table for storing information including a number in a display order determined by the decoding order and the picture type; and a stream structure analysis circuit for controlling the storage. Refers to the decoding order in the display order of the stream structure table or in the reverse order. And controls the read, also, the decoder is characterized in that to skip decoding in time by the coding type in the stream structure table.

Further, in a preferred embodiment of the compressed stream decoding apparatus according to the present invention, in the display order, if a frame output from the bit string storage memory is a core picture, the display order is reserved until a frame output of the next core picture. Then, the information is written in the stream structure table, and if the frame output from the bit string storage memory is a B picture, the information is immediately written in the stream structure table.

According to the present invention, the encoding type is displayed, the decoding order is automatically generated at the time of normal reproduction of the frame read from the recording medium in the decoding order, and the decoding order and the encoding type are calculated based on the decoding order. Paying attention to the point that the display order of the frames is determined, the decoding order and the encoding type are stored in the stream structure table in the display order, and at the time of special playback such as reverse playback, this stream structure table is displayed in the display order or reverse order, Reading and controlling the frame with reference to the decoding order number and skipping the decoding in a timely manner according to the encoding type enable accurate and quick trick play while keeping the size of the stream structure table small. Became.

[0040]

Next, an embodiment of the present invention will be described.

As shown in FIG. 1, the compressed stream decoding apparatus according to the present invention comprises an optical disk medium 1 on which a compressed stream encoded by an inter-frame predictive encoding system is recorded, and a continuous stream from the optical disk medium 1. V in GOP configuration
Data reading circuit 2 for reading a frame in OBU units
A bit string storage memory 3 for storing the read VOBU-based frames, a read control circuit 4 for controlling the data read circuit 2 and the bit string storage memory 3,
A decoder 5 for decoding a frame read from the bit string storage memory 3; and three frame memories 61 for storing the latest three frames of the core picture among the decoded frames and referred to when decoding a B-type frame. , 62,
63, and a stream structure table 7 for storing information including the decoding order and the picture type in the display order determined by the decoding order and the picture type for the frame read from the bit string storage memory 3 during normal playback, A stream structure analysis circuit 8 for controlling storage, and at the time of trick play, the read control circuit 2 controls reading by referring to the decoding order in the display order of the stream structure table 7 or in the reverse order. Also, the decoder 5 has a stream structure table 7
It is characterized in that decoding is skipped in a timely manner according to the middle picture type. Here, the decoding order is a number indicating the number of a picture recorded in a certain GOP from the top of the GOP.

The outline of the operation of the present embodiment is as follows. First, the operation during forward reproduction will be described. When the user drives the optical disk medium 1, the data readout circuit 2 reads a GOP (Group Of) from the optical disk medium 1.
Picture), the frames are read out in the order of the serial number, and V
The data is written to the bit string storage memory 3 in OBU units. Here, the VOBU unit is a Video Object U
It is an abbreviation of nit and is defined by the DVD standard. Here, two GOPs are defined as one VOBU unit. The frames are read out in the order in which they were written and input to the decoder 5. The I picture or P picture (referred to as core picture) frame is decoded by the decoder 5, and the B picture is referred to the two immediately preceding core pictures stored in the frame memories 61 to 63. Is decrypted.

At this time, the stream structure analysis circuit 8
The decoding order is generated for the frames read in the decoding order, and information including the decoding order and the picture type is written to the stream structure table 7 in the display order of the frames. This display order is determined by the decoding order and the picture type due to the characteristics of the stream.

Next, the operation at the time of reverse reproduction will be described. When the user specifies reverse reproduction, the data read circuit 2
Reads frames from the optical disk medium 1 in the order of GOP serial numbers and writes the frames to the bit string storage memory 3 in VOBU units. The read control circuit 4 reads the stream structure table 7
Are read out from the bit string storage memory 3 to the decoder 5 by referring to the GOP numbers in reverse order and in the GOP in the reverse order of the display order of the frames. At this time, since the decoding order, that is, the order from the first frame in each GOP in the bit string storage memory 3 is written in the stream structure table 7, the read position of the frame in the bit string storage memory 3 is immediately determined. .

In the decoder 5, if it is a core picture, it is decoded, stored in the frame memories 61 to 63, and the frame is output. At this time, B is used to decode the P picture.
Since a picture is unnecessary, a B picture between the P picture and the core picture three pictures before is skipped. If the frame is a B picture, it is decoded with reference to the frame memories 61 to 63.

Next, an embodiment of the present invention will be described in detail with reference to FIGS.

FIG. 2 shows a bit string storage memory 3 and a stream structure analysis circuit 8 for creating the stream structure table 7.
FIG. 4 is a block diagram showing the details of. Bit string storage memory 3
Is composed of a GOP header and a plurality of frames, and each frame is composed of a header and image data. The frames are arranged in the decoding order within the GOP, and the header of each frame records the GOP number, picture type, display order, and open / close. In the MPEG standard, open / close is called a Closed-GOP flag. GOP number is V
The number and picture type of the GOP in the OBU are I pictures, P pictures, and B pictures, and the display order is the display order of the frame in the GOP.
The difference between open and closed refers to whether the immediately preceding GOP is referenced (open) or not referenced (closed) when decoding a B-picture at a GOP boundary.

At the time of normal reproduction, the stream structure table 7
However, the above-mentioned open / closed and GOP numbers are directly written from the bit string storage memory 3 as they are. However, the decoding order and the picture type go through the stream structure analysis circuit 8.

As shown in FIG. 2, the stream structure analysis circuit 8 reads a header of a frame stored in the bit string storage memory 3 to determine whether or not the frame is the B type. The decoding order counter 82 that counts the number of frames from the first frame to the frame in the GOP, and if the picture type discriminator 81 determines that the type is B, the picture type in the bit string storage memory 3 is written as is to the stream structure table 7 Otherwise, the selector 83 for writing to the core picture temporal memory 86, and the value of the decoding order counter 82 when the picture type discriminator 81 determines that the type is B, the stream structure table 7
And the selector 84 for writing to the core picture temporal memory 86 if not, and the picture type discriminator 81 is opened when it is determined to be B type. Otherwise, it is closed and the core picture temporal memory 86 is closed. Contents as stream structure table 7
And a core picture temporal memory 86 for storing the decoding order and picture type as described above.

FIG. 3 is a flowchart showing an operation of writing to the stream structure table 7 by the stream structure analysis circuit 8. First, frames are read from the optical disk medium 1 in the order of GOP serial numbers, written into the bit string storage memory 3 in VOBU units, and the decoding order counter 82 is reset to an initial value “1”. Then, the GOP number of the GOP header part and the open
The information for each close and the picture type of the header part of the frame are fetched (step S1 in FIG. 3), and the picture type discriminator 81 determines whether the picture type is a B picture (S2). If it is a B picture, the decoding order counter 82 increments the decoding order by adding 1 to the count value (S3), and the stream structure analysis circuit 8 determines the decoding order, picture type, open / closed, and GOP number in the stream structure. Write to Table 7 (S4).
If it is determined in S2 that the type is not the B type,
The decoding order counter 82 increments the decoding order by incrementing the count value by one (S5). The decoding order and the picture type, which are the contents of the immediately preceding core picture temporal memory 86, are written into the stream structure table 7 (S
6) The current decoded data, that is, the decoding order and the picture type at this time are stored in the core picture temporal memory 8.
6 (S7).

FIG. 4 shows that the input stream is I ₂ B ₀ B ₁ P
₅ B ₃ B ₄ P ₈ B ₆ B ₇ , that is, the core picture temporal memory 86 and stream structure table 7 for GOP 1 written in the bit string storage memory 3 in this order.
Is shown. The open / close status is set to open “0”.

[0052] with respect to I ₂ in decoding order 1 is written the contents of the previous core picture for temporal memory 86 to the stream structure Table 7, now being empty as unknown. The decoding number “1” and the picture type “I” at this time are written in the core picture temporal memory 86.

[0053] B ₁ of the next decoding order 2 of B ₀ and the decoding order 3
, The decoding order “2”, “3” and the picture type “B” at that time are the first row and the second row of the stream structure table 7.
Written in the line, the core picture temporal memory 8
6 is unchanged.

[0054] At P ₅ of the decoding order 4, just before, i.e., decoding order is the content of the core picture for temporal memory 86 in 3 of B _1, picture type "I" and the stream structure table and decoding order "1" 7 is written to the third line. Then, the core picture temporal memory 86
, The decoding order “4” and the picture type “P” at this time are written.

For the other B pictures B ₃ , B ₄ , B ₆ , B ₇ and P picture P ₈ , the stream structure table 7 and the core picture temporal memory 86 are similarly written. Here, it should be noted that the writing order in the stream structure table 7 is the display order, that is, the order of the numbers indicated by the subscripts of the input stream. This is realized by temporarily storing the decoding order and the picture type in the core picture temporal memory 86 if the input stream is a core picture, and then writing the stream in the stream structure table 7 when the next core picture appears. It is.

Next, the operation at the time of reverse reproduction of the present invention using the stream structure table 7 created as described above will be described with a specific example.

FIG. 5 shows a case where the input stream shown in FIG.
Time # 1 for normal playback up to ₆ , ie, forward playback
FIG. 24 is a diagram for explaining a decoding operation in the case of performing reverse reproduction after time, in a time-series manner. B ₆ is the picture of the seventh frame, and it is clear from FIG. 4 that the value of the decoding order counter 82 is “8”. The read control circuit 4 performs the reverse order from the seventh row of the stream structure table 7. The bit string storage memory 3 is read out while referring to.

Next to B ₆ is to display P of the sixth frame.
₅ , which is stored on the sixth row of the stream structure table 7 in FIG. 4 as the decoding order “4”, which is adjacent to the left of the decoding order “8”. Thus, in the time # 2 is read from the head of I ₂ bit string storage memory 3 into four frames I ₂ B ₀ B ₁ P ₅ decoder 5. I ₂ is decoded and written into the frame memory 61, B ₀ and B ₁ skip decoding, and P ₅ is decoded and output with reference to I _{2 of the} frame memory 61. P ₅ is the frame memory 6
2 is written.

[0059] It should be displayed next to the P _{5 5} th frame of the B
₄ , which is stored on the left side of the decoding order “4” as the decoding order is “6” in the stream structure table 7 in FIG. Therefore, at time # 3, the six frames I ₂ B ₀ B from the beginning of bit string storage memory 3
₁ P ₅ B ₃ B ₄ is read out to the decoder 5. The decoding of I _{2 to} B ₃ is skipped, and B ₄ is the I _{2 of the} frame memory 61.
And with reference to the P ₅ in the frame memory 62 and decodes and outputs.

[0060] It should be displayed next to the B ₄ is B _3, as shown in the time # 4 and is decoded in the same manner as the B ₄ is outputted. While following B ₃ is I _2, which has already been decoded, since the stored in the frame memory 61 may be output. As described above, if the stream structure table 7 is referred to in the reverse order, the read position of the bit string storage memory 3 can be quickly determined, and decoding can be performed quickly.

After I ₂ , B ₁ should be displayed.
Decoding of ₁ requires I ₂ and the last core picture of the previous GOP0. In this case, if the stream structure table 7 by an open-close is only to be open (1), it can not decode the B ₁ and B _0, the decoding of the GOP at this time is ended.

FIG. 6 shows that the I _{2 of} GOP # (n + 1) is open (O) when the open / close state is set to open (O).
(Time # 1), and then GOP # (n
Following B _1, B ₀ of +1), P ₈ of GOP # n, B ₇
The state of decoding is shown in time series.

[0063] For the decoding of B ₁ of GOP # (n + 1) GOP # to be displayed next I ₂ of (n + 1) is, GOP
# Other I ₂ of (n + 1), it is necessary to P ₈ in the GOP # n. In this case, as shown at time # 2, in addition to the three frames I ₂ B ₀ B ₁ from the head of GOP # (n + 1) according to stream structure table 7, all frames I ₂ B ₀ B of GOP #n reading of _{1 P 5 B 3 B 4 P} 8 B 6 B 7 is. Accordingly, B ₁ of GOP # (n + 1) becomes G
OP # (n + 1) is decoded as a reference frame and a P ₈ of I ₂ and GOP # n of the output. GOP # (n + 1)
B ₀ is the same (time # 3).

B of GOP # (n + 1)₀ Should be displayed after
Kiha GOP # n P₈ But 2GOP in advance
Prepare a stream structure table for (VOBU units)
The decoding order, picture type, etc. for this are shown in FIG.
In the table corresponding to the previous temporal memo for the core picture.
“7” and “P”, which are the contents of the file 86, are GOP numbers #n.
Both are written. Therefore, at time # 4
So, I of GOP # n _Two B₀ B₁ P_Five B_Three B_Four P₈ 
Is read out, and P of GOP # n is read._Five As a reference frame
P₈ Is decoded and output.

[0065] It should be displayed next to the P ₈ is B _7, the stream structure table 7, the rightmost picture information GOP # n, I ₂ B of _{GOP # n 0 B 1 P 5} B 3 B 4 P ₈
B ₆ B ₇ is read. Since P ₈ is already stored in the frame memory 63 is decoded by referring to the P ₅ of GOP # n, B ₇ is decoded and output.

In the above description, the reverse reproduction is described as a typical example of the special reproduction. However, when performing the skip reproduction regardless of the forward reproduction or the reverse reproduction, the stream structure table 7 is used.
May be read out at a position skipped by a predetermined address. Also, it is easy to reproduce from a specific position in the GOP by using skip reproduction.

[0067]

According to the present invention, the decoding order is automatically generated at the time of normal reproduction from the input stream in the decoding order, and this is stored, so that a reading error of the temporal reference is eliminated and a high quality reproduced image is obtained. The first effect is that it can be performed.

Since the decoding order and the picture type are stored in the order in which the images are displayed, decoding and decoding skipping frames can be instantaneously determined even during special reproduction such as reverse reproduction, and rapid special reproduction is performed. The second that is possible
Has the effect of

The stream structure table also has an effect that it can be configured with a smaller storage capacity than a conventional search table.

[Brief description of the drawings]

FIG. 1 is a block diagram of a compressed stream decoding apparatus according to the present invention.

FIG. 2 is a block diagram showing a main part of the stream structure analysis circuit shown in FIG. 1;

FIG. 3 is a flowchart of creating a stream structure table by a stream structure analysis circuit;

FIG. 4 is a diagram showing a specific example of a stream structure table and storage contents of a core picture temporal memory.

FIG. 5 is a diagram for explaining a reverse reproduction operation in the same GOP according to the present invention;

FIG. 6 is a diagram for explaining a reverse reproduction operation between GOPs according to the present invention;

FIG. 7 is a block diagram of an example of a conventional stream compression / decoding apparatus.

FIG. 8 is a diagram showing a plurality of temporally continuous image frames in the MEPG method.

FIG. 9 is a diagram showing a bit string obtained by encoding a GOP according to the MPEG method.

FIG. 10 shows a conventional GOP (n +
Diagram for explaining bit string syntax of 1)

FIG. 11 is a diagram for explaining an operation at the time of reverse reproduction in the conventional example shown in FIG. 7;

[Explanation of symbols]

 Reference Signs List 1 optical disk medium 2 data read circuit 3 bit string storage memory 4 read control circuit 5 decoder 7 stream structure table 8 stream structure analysis circuit 61, 62, 63 frame memory 81 picture type discriminator 82 decoding order counter 83, 84 selector 85 switch 86 Temporal memory for core pictures

 ──────────────────────────────────────────────────続 き Continued on the front page F-term (reference) SS13 SS16 SS18 UA05 UA33 UA36

Claims (11)

[Claims] 1. A compressed stream decoding method for decoding a compressed stream coded by an inter-frame predictive coding method, comprising the steps of: Information including the encoding type is stored in a display order determined by the decoding order and the encoding type, and during special playback,
A compressed stream decoding method, characterized in that decoding is performed while referring to the decoding order in the display order or the reverse order, and skipping timely according to the encoding type. 2. A compressed stream decoding method for decoding a compressed stream encoded by an inter-frame predictive encoding method, comprising the steps of: reading a group of frames from a medium recording the compressed stream; Storing the group of frames in the bit string storage memory, reading the frames from the bit string storage memory, decoding only the frames of the first encoding type out of the read frames, A procedure of storing a predetermined frame among the decoded frames in a frame memory, and a procedure of decoding only a frame of a second encoding type among the frames read from the bit string storage memory with reference to the frame memory During normal reproduction, the decoding order and the encoding time of the frame read from the bit string storage memory are determined. And information stored in the stream structure table in a display order determined by the decoding order and the encoding type, and at the time of trick play, the display order of the stream structure table or A method of decoding a compressed stream, comprising: a step of controlling reading of the frame by referring to the decoding order in reverse order; and a step of skipping decoding in a timely manner according to the coding type. 3. A compressed stream decoding method for decoding a compressed stream encoded according to the MPEG system, comprising the steps of:
A procedure for reading a frame in VOBU units of the OP configuration,
Storing the read VOBU-based frame in the bit string storage memory, reading the frame from the bit string storage memory, decoding only the core picture frame among the read frames, A procedure of storing the latest three frames among the decoded frames in a frame memory, a procedure of decoding only a B picture frame among the frames read from the bit string storage memory with reference to the frame memory, At the time of reproduction, for a frame read from the bit string storage memory, information including a decoding order, a picture type, and a GOP number is stored in a stream structure table in a display order determined by the decoding order and the picture type. During special playback, the display order of the stream structure table or A method for decoding a compressed stream, comprising: a step of controlling reading of the frame by referring to a decoding order in reverse order to the decoding order; and a step of skipping decoding in a timely manner according to the coding type. 4. The display order is as follows. If the frame output from the bit string storage memory is a core picture, the information is reserved until the next core picture frame output, and the information is written into the stream structure table. 4. The compressed stream decoding method according to claim 3, wherein if the frame output from the memory is a B picture, the information is formed by immediately writing the information into the stream configuration table. 5. The information stored in the stream configuration table includes:
5. The decoding method according to claim 3, wherein when decoding a B picture included in the GOP, an open / close flag indicating whether to refer to a frame of another GOP is included. Compressed stream decoding method. 6. The compressed stream decoding method according to claim 3, wherein a frame is read in GOP units instead of in VOBU units. 7. When the trick play is a reverse play,
7. The compressed stream decoding method according to claim 3, wherein the stream structure table is read in the reverse order of storage order. 8. The compressed stream decoding apparatus according to claim 3, wherein when the trick play is skip playback, the stream structure table is skipped by a predetermined number and read. Method. 9. A compressed stream decoding apparatus for decoding a compressed stream encoded by an inter-frame predictive encoding method, comprising: a recording medium on which the compressed stream is recorded; and a group of frames read out from the recording medium. Means, bit string storage means for storing the read group of frames, read control means for controlling the read means and bit string storage means, and decoding means for decoding the frames read from the bit string storage means And a frame memory means for storing a predetermined frame of a first encoding type among the decoded frames, which is referred to at the time of decoding of the second encoding type, and For the read frame, information including the decoding order and the encoding type is defined by the decoding order and the encoding type. A stream structure table for storing the entire data in display order; and a stream structure analysis means for controlling the storage. At the time of trick play, the read control means displays the stream structure table in display order or reverse order. Wherein the decoding control is performed by referring to the decoding order, and the decoding means skips decoding in a timely manner according to an encoding type in the stream structure. 10. A compressed stream decoding apparatus for decoding a compressed stream encoded by the MPEG system, comprising: a recording medium on which the compressed stream is recorded; and a frame from the recording medium in units of VOBUs having a continuous GOP structure. A data read circuit to be read, and the read VOB
A bit string storage memory for storing a frame in U units, a read control circuit for controlling the data readout circuit and the bit string storage memory, a decoder for decoding a frame read from the bit string storage memory, and the decoded frame Among the three frames of the core picture stored therein, a frame memory referred to at the time of decoding the B-type frame and a frame read from the bit string storage memory during normal reproduction, the decoding order and the picture type are set. A stream structure table for storing information including a GOP number in a display order determined by the decoding order and the picture type; and a stream structure analysis circuit for controlling the storage. The circuit refers to the decoding order in the display order of the stream structure table or in the reverse order. The compressed stream decoding apparatus according to claim 1, wherein the decoding is controlled by the decoder according to an encoding type in the stream structure table. 11. The display order is as follows: if the frame output from the bit string storage memory is a core picture, the information is written to the stream structure table while retaining the frame output of the next core picture, and the bit string storage is performed. 11. The compressed stream decoding device according to claim 10, wherein if the frame output from the memory is a B picture, the information is formed by immediately writing the information to the stream structure table.