JPH0818984A - Information reproducing device - Google Patents

Abstract

PURPOSE:To return to an ordinary operation by suppressing the deterioration of an image even when a reproducing error occurs due to the readout error of information from an information recording medium by performing error recovery corresponding to each hierarchy when a hierarchical error occurs in reproduction. CONSTITUTION:A video stream inputted to a terminal 200 is inputted to a decoder circuit 202 of variable length code via a buffer 201. The circuit 202 performs variable length encoding of inputted data, and sends the DCT coefficients and the quantization step information of a decoded image to an inverse quantization circuit 203. The circuit 203 performs the inverse quantization of the data. and a circuit 204 applies inverse DCT processing to it, and outputs macro clock data via a changeover switch 205, or outputs data sent from an adder 26. While, a sequencer 300 for control recovers the error of each layer of a block layer, a macro block layer, a slice layer, a picture layer, a GOP layer and a video sequence layer corresponding to each hierarchy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to an information recording medium such as a CD-ROM or a CD-I (CD-Interactive) which is a read-only memory using a so-called compact disc. The present invention relates to an information reproducing device for reproducing information provided by a user.

[0002]

2. Description of the Related Art Conventionally, various methods for compressing and coding an image signal have been proposed. As a specific example thereof, for example, there is a so-called MPEG (International Standardization Working Group for color moving picture coding system). Moving Picture Exp
ert Group) method. This MPEG system is a so-called high-efficiency coding system for image signals for so-called digital storage media, and the image of a frame is an I picture (Intra-coded picture), P picture (forward predictive coded image: Perdictive-coded picture) or B picture (bidirectional predictive coded image: Bidirectio
Any one of the three types of pictures (nally-coded picture) is used to compress and code the image signal.

The principle of the high-efficiency coding system of the image signal by the MPEG is as follows.

That is, in this high-efficiency coding system, the redundancy in the time axis direction is first reduced by taking the difference between the images, and then so-called discrete cosine transform (DCT) processing and variable length coding are used. The redundancy in the spatial axis direction is reduced.

First, the redundancy along the time axis will be described below.

Generally, in a continuous moving image, temporally preceding and succeeding images are very similar to an image of interest (that is, an image at a certain time). For this reason,
For example, as shown in FIG. 4, if the difference between the image to be encoded now and the image ahead in time is calculated and the difference is transmitted, the redundancy in the time axis direction is reduced and transmission is performed. It is possible to reduce the amount of information to be stored. An image encoded in this way is called the P picture. Similarly, the difference between the above-mentioned image to be encoded now and the interpolated image formed from the front or the rear in time, or the front and the rear in time is taken, and the difference of a smaller value is transmitted. By doing so, it becomes possible to reduce the amount of information to be transmitted by reducing the redundancy in the time axis direction. The image coded in this way is B
Called a picture. In addition, in FIG. 4, I in FIG.
The image shown by means the I picture, the image shown by P in the drawing shows the P picture, and the image shown by B in the drawing shows the B picture.

Next, the redundancy in the spatial axis direction will be described below.

The difference of the image data is not transmitted as it is, but discrete cosine transform (DCT) is applied to each unit block of 8 × 8 pixels. The DCT represents an image not by the pixel level but by how many frequency components of the cosine function are included, and for example, a two-dimensional D
By CT, the data of the unit block of 8 × 8 pixels is 2
It is transformed into a coefficient block of 8 × 8 cosine function components by the dimension DCT. For example, an image signal of a natural image taken by a television camera is often a smooth signal. In this case, the data amount can be efficiently reduced by performing the DCT process on the image signal.

That is, in the case of a smooth signal such as an image signal of a natural image, by applying the DCT, large values are concentrated around a certain coefficient.
When this coefficient is quantized, most of the 8 × 8 coefficient block becomes 0, and only large coefficients remain. Therefore, when transmitting the data of the 8 × 8 coefficient block, a set of so-called zigzag scans and non-zero coefficients and so-called 0 runs indicating how many 0s precede the coefficient are set. By transmitting the so-called Huffman code, the transmission amount can be reduced. On the decoder side, the image is reconstructed in the reverse procedure.

Next, FIG. 5 shows the structure of data handled by the above-mentioned MPEG system. That is, the data structure shown in FIG. 5 is composed of a block layer, a macroblock layer, a slice layer, a picture layer, a group of picture (GOP) layer, and a video sequence layer in order from the bottom. It has a hierarchical structure. Hereinafter, in FIG. 5, the layers will be described in order from the bottom.

First, in the block layer, the unit blocks of the block layer are adjacent to each other in the luminance or color difference of 8 ×.
It is composed of 8 pixels (8 lines × 8 pixels).
The DCT (discrete cosine transform) described above is applied to each unit block.

In the macroblock layer, the macroblock of the macroblock layer is composed of four luminance blocks (luminance unit blocks) Y0, which are adjacent to each other in the left-right direction and the upper-lower direction.
Y1, Y2, Y3 and a color difference block (color difference unit block) C corresponding to the same position as the luminance block on the image
It is composed of 6 blocks in total including r and Cb. The order of transmission of these blocks is Y0, Y1, Y2, Y3, C
The order is r and Cb. Here, in the encoding method, what is used for a prediction image (reference image for taking a difference),
Alternatively, whether or not the difference need not be sent is determined in units of this macroblock.

The slice layer is composed of one or a plurality of macroblocks which are continuous in the scanning order of the image. At the beginning (header) of this slice, the difference between the motion vector and the DC (direct current) component in the image is reset, and the first macroblock has data indicating the position in the image, and thus the error is It is designed to be able to return even if it happens. Therefore, the length and starting position of the slice are arbitrary and can be changed depending on the error state of the transmission path.

In the picture layer, each picture, that is, each image is composed of at least one or a plurality of slices. Each of the I picture, P picture, B picture, and DC intra-coded image (DC coded (D) pictur) is encoded according to the encoding method.
It is classified into four types of images of e).

Here, in the above-mentioned I picture, only information closed in one image is used at the time of encoding. Therefore, in other words, the image can be reconstructed only with the information of the I picture itself when decoding. Actually, the DCT processing is performed as it is and the encoding is performed without taking the difference. This encoding method is generally inefficient, but if this encoding method is put everywhere, random access and high-speed reproduction are possible.

In the P picture, an I picture or a P picture which is located in a temporally previous position at the input and has already been decoded is used as a prediction image (image serving as a reference for taking a difference). Actually, whichever is more efficient, that is, the difference between the motion-compensated predicted image and the predicted image is encoded, or the difference is directly encoded without taking the difference (intra-code) is selected for each macro block.

In the B picture, three types of I picture or P picture, which is positioned in front in time and has already been decoded, and an interpolated picture made from both of them, are used as predictive pictures. This makes it possible to select the most efficient one of the above three types of differential encoding after motion compensation and the intra code in macroblock units.

The DC intra-coded image is an intra-coded image composed only of DC coefficients of DCT,
It cannot exist in the same sequence as the other three types of images.

The group of pictures (GOP) layer includes one or a plurality of I pictures and 0 or a plurality of non-I pictures.
And a picture. Here, the input order to the encoder is, for example, 1I, 2B, 3B, 4P * 5B, 6
B, 7I, 8B, 9B, 10I, 11B, 12B, 13
P, 14B, 15B, 16P * 17B, 18B, 19
When I, 20B, 21B and 22P are used, the output of the encoder, that is, the input of the decoder is, for example, 1I, 4
P, 2B, 3B * 7I, 5B, 6B, 10I, 8B, 9
B, 13P, 11B, 12B, 16P, 14B, 15B
* 19I, 17B, 18B, 22P, 20B, 21B. In this way, the order is changed in the encoder, for example, when the B picture is encoded or decoded, the I picture or P that is the temporally backward prediction image is the predicted image. This is because the picture must be encoded first. Here, the interval of the I picture (for example, 9) and the interval of the I picture or the B picture (for example, 3) are free. Also, I picture or P
The picture interval may change within the group of pictures layer. The break in the group of pictures layer is represented by *. Further, the I is an I picture, the P is a P picture, and the B is a B picture.

The video sequence layer includes an image size,
It is composed of one or more group of picture layers having the same image rate and the like.

As described above, when transmitting a moving image compressed and encoded by the MPEG system, an image obtained by compressing one image in a picture is first sent, and then this image is motion-compensated. The difference from the image is transmitted.

Further, the coded bit stream having the structure of FIG. 5 will be described in more detail.

The video sequence layer is a 32-bit sequence code (sequence star) indicating the beginning of the video sequence layer.
t code) and 12-bit information indicating the number of horizontal pixels in the image
(horizontal size) and 12 indicating the number of vertical lines in the image
Bit information (vertical size) and 4-bit information (pel aspectra) that is an index indicating the aspect ratio of the pixel interval
tio), 4-bit information (picture rate) that is the index of the pixel display rate, information (bit rate) that is a bit rate for limiting the amount of generated bits and rounded up in 400 bit units, and "1" 1-bit information (reserved bit), a 10-bit parameter (buffer size) that determines the size of the virtual buffer for limiting the amount of generated bits, and that each parameter is within the determined limit 1 Bit flags (constrained pe
rameter flag) and a 1-bit flag (load in) indicating the presence of quantization matrix data for intra macroblocks.
tarqunatize matrix) and 8 × 63-bit information indicating the quantization matrix for intra macroblocks (intar
qunatize matrix) and a 32-bit (load no
n intar qunatize matrix) j, 8 × 64-bit information (non intar qunatize matrix) indicating a quantization matrix for a non-intra macroblock, and a 32-bit synchronization code (extension start co
de), 8-bit × n information (sequence extension byte) determined by ISO for future compatibility, and a 32-bit synchronization code (user dat) indicating that there is user data.
a start code), 8-bit xn information for the user's application (user data), and a 32-bit synchronization code (sequence e) indicating the end of one or more sequences.
nd code) and.

The group of picture layer is a 32-bit synchronization code (group start code) indicating the start of GOP.
, A 25-bit code (time code) that indicates the time from the beginning of the sequence, and a 1-bit flag (closed gop) that indicates that the image in the GOP can be reconstructed without using the data of other GOPs. The 1-bit flag (broken
-link), a 32-bit synchronization code (extension start code) indicating that there is extension data, and 8-bit × n information (group extension) determined by ISO for future compatibility.
sion byte), 32-bit synchronization code (user data start code) indicating that there is user data, and 8 bits x n information (user data) for the user application.
And 1 or more I-pictures and 0 or more I-pictures other than I-pictures (picture layer data).

The picture layer includes a 32-bit synchronization code (picture start code) indicating the beginning of the picture layer, and a 1024 10-bit residual value (temporal reference) reset at the head of the GOP with a value indicating the display order. A 3-bit value (p indicating the image coding mode (picture type)
icture coding type) and 16-bit parameter (buff
er fullness) and 1-bit information that is present in a B or P picture and that indicates the accuracy of the motion vector in pixel units or half pixels (full pel forward vector) and 3-bit information that indicates the search range of the forward motion vector. Information (forward f),
1-bit information that exists in the B picture and indicates whether the motion vector accuracy is in pixel units or half pixels (full pel backward
vector) and 3-bit information (backward f) indicating the backward motion vector search range, and a 1-bit × n flag (extra bi) indicating that there is an extra information picture.
tpicture) and ISO for future applications 8
Bit xn information (extra information picture), 16-bit "0" information indicating that the above flag (extra bit picture) does not exist, and 3 indicating that there is extended data.
2-bit sync code (extra bit code) and 8-bit xn information (extr determined by ISO for future compatibility)
a information picture) and a 32-bit synchronization code (extension start code) indicating that there is user data
And 8 bits x n information for the user's application
(picture extension data) and one or more slice layer data (slice layer data).

The slice layer includes a 32-bit synchronization code (slice start code) indicating the beginning of the slice layer, 5-bit data (qunatize scale) giving a quantization width used in the slice, and an extra information picture. 1-bit x n flag (extra bit scale)
And 8 bits xn determined by ISO for future applications
Information (extra information scale) and the above information (extr
a information picture), which is 16-bit "0" information indicating that there is no information picture) and one or more macroblock layer data (macroblock layer data).

The macroblock layer is used for rate control 1
1-bit dummy code (macroblock stuffing), 11-bit code (macroblock escape) corresponding to 33 skip macroblocks, and the left end of the variable-length coded image representing the number of skip macroblocks before the macroblock + 1 From 1 to 11 representing the number of macroblocks + 1
Bit information (macro block address increment) and 1 to 8 bit information (macro block type) that exists when the macro block type has a value that indicates the quantization width with a variable length code that indicates the coding mode of the macro block. ), A 5-bit value (qunatize scale) indicating the quantization width after the macroblock, and when the macroblock type is forward and bidirectional prediction, the horizontal component of the forward motion vector of the macroblock and the previous macro are present. Information of 1 to 14 bits (motiom horizontal forward), which is obtained by encoding the difference between the vector of the block and the vector (variable length encoding) represented by the above information (forward f), and 1 which is the vertical component of the backward motion vector. ~ 14-bit information (motiom vertica
l backward), 30-bit information (coded block pattern) that is information of a variable length code indicating whether or not the macro block has coefficients of 6 blocks, and the above information (coded block pattern). The data of the block layer shown to be Y ₀ , Y ₁ , Y ₂ , Y ₃ , Cr, C
Information of blocks 1 to 6 indicating that the data is b (block laye
r data) and 1-bit “1” information that exists only for D pictures and indicates the end of a macroblock (end of macro
block) and.

The block layer exists at the time of an intra macro block and represents the number of bits of the next DCT and DC difference.
7-bit variable length code information (dct dc ltuminace), (dct
dc size chrominance) and 1- to 8-bit variable length code information (dct dc differential) of the DC component of the block before the DC component of the block and DC component of the DC component of the block. 2 to 28-bit variable length code information (dctcoef first) and DCT coefficient
The information of the variable length code of 2 to 28 bits (dct coef next), which is a combination of the coefficient of 0 and the number of 0 coefficients immediately before it, is sent in the zigzag order from the C component and the subsequent information in that block. It consists of a 2-bit code (end of block) indicating that the coefficients are all zero.

[0029]

By the way, from the past,
The information recording medium is, for example, a so-called compact disc (that is, CD-DA: compact disc digital disc) in which an audio signal is recorded on an optical disc.
Audio) is present.

However, in the CD-DA (hereinafter referred to as an audio CD) for recording only the audio signal, only the data of the sound is divided and recorded in the unit of track, so that, for example, the program for controlling the reproducing function is used. You cannot put a script or script. Also, the reproduction order is merely linear reproduction or reproduction in the order instructed by the user, and there is no freedom even if the content supplier wants to reproduce in various other orders.

On the other hand, the so-called CD-I (CD-
Interactive: CD-Interactive) allows you to handle sounds, movies, and still images as data files.

When recording a moving image on a disc capable of recording such sounds, moving images, still images, etc., the moving image of the MPEG format as described above is recorded in consideration of the recordable capacity of the disc. Is desirable.

However, when an error occurs in the decoding sequence of the reproducing apparatus due to the read error of the bit stream of the moving image compressed and encoded in the MPEG format, the image is deteriorated.

In view of the above, the present invention suppresses the deterioration of the image as much as possible even if a reproduction error occurs due to a data read error from the disk,
It is an object to provide an information reproducing device that can return to normal operation.

[0035]

DISCLOSURE OF THE INVENTION The present invention has been proposed in order to achieve the above object, and reproduces an information recording medium in which a predetermined moving image sequence composed of a plurality of hierarchical information is recorded. The information reproducing apparatus according to the present invention is characterized by having an error recovery means for recovering an error of each layer information according to each layer.

Here, regarding the error in the first layer information which is the lowermost layer among the plurality of layer information, the error recovery means averages the second layer information composed of a plurality of the first layer information. Perform error recovery using the value.

In addition to or in addition to the error recovery, the error recovery means may detect the error in the second layer information including a plurality of the first layer information which is the lowest layer among the plurality of layer information. Error recovery is performed by replacing with information of the image preceding or succeeding in time up to the next start position of the third hierarchical information composed of a plurality of second hierarchical information or the final position of the image including the second hierarchical information. Or third
Error information is restored by replacing with predetermined information up to the next start position of the layer information or the last position of the image including the second layer information, or the next start position of the third layer information or the second position information. The error recovery is performed by deleting the information up to the last position of the image including the hierarchy information, or the error recovery is performed by returning to the start position of the third hierarchy information.

Further, in addition to or in addition to the error recovery, the error recovery means skips the error in the hierarchy information higher than the third hierarchy information to the start position of the next higher hierarchy information. , Perform error recovery.

[0039]

According to the present invention, if an error of each layer information occurs when an information recording medium in which a predetermined moving picture sequence composed of a plurality of layer information is recorded is reproduced, it is possible to respond to each layer. Error recovery.

[0040]

An embodiment of the present invention will be described below with reference to the drawings.

The information reproducing apparatus of the embodiment of the present invention is an information recording medium (for example, a so-called video CD) on which the above-mentioned moving picture sequence of the MPEG format is recorded as a predetermined moving picture sequence composed of a plurality of layer information.
An information reproducing apparatus for reproducing a block layer, a macroblock layer, a slice layer, a picture layer, a GOP layer,
As shown in FIG. 1, it has a control sequencer 300 composed of, for example, an LSI (Large Scale Integrated Circuit) as error recovery means for recovering an error in each layer information of the video sequence layer according to each layer. It is what

Here, the control sequencer 300 is
Regarding an error in the block layer as the first layer, which is the lowest layer among the plurality of layers, error recovery (error recovery) is performed using the average value of each block of the macroblock layer, which is the second layer. To do.

In addition to or in addition to the above error recovery, the control sequencer 300, for an error in the macroblock layer, the next start position (slice start code (slice start code) of the slice layer which is the third layer).
e)) or until the last position of the image including the macroblock layer is replaced with information of a temporally previous or subsequent image (forward side in I and P pictures, backward side in B picture) to perform error recovery. , Predetermined information up to the next slice start code (slice start code) or the last position of the image containing the macroblock (for example, a specific unobtrusive color such as white, black, gray, blue, green, or orange) Or before and / or after average) to perform error recovery, delete the next slice start code (slice start code) or information up to the last position of the image containing the macroblock. Error recovery or slice start code (slice s
Return to tart code) and perform error recovery.

Further, the control sequencer 300 is
Regarding errors in the information of the picture layer, GOP layer, and video sequence layer, which are layers higher than the slice layer, the start position (picture start code) , Group start code (group start code), sequence start code (sequence start code)) and skip error recovery.

Hereinafter, FIG. 1 will be described. In FIG. 1, which shows a schematic configuration of an information reproducing apparatus according to an embodiment of the present invention, a terminal 200 is supplied with a video bit stream in a so-called MPEG1 format. This bit stream is once stored in a bit stream buffer 201 including a frame memory, then read out, and sent to a variable length code decoding circuit 202. The variable length code decoding circuit 202 uses the bit stream buffer 2
The data supplied from 01 is subjected to variable length decoding, and the DCT coefficient of the decoded image, quantization step information and the like are sent to the inverse quantization circuit 203. The inverse quantization circuit 203 performs an inverse quantization process corresponding to the quantization at the time of encoding, and further the next inverse DCT circuit 204 performs an inverse DCT process corresponding to the DCT at the time of encoding. All of these processes are performed in macroblock units.

The output from the inverse DCT circuit 204 is supplied to one switched terminal of the changeover switch 205 and is also sent to the adder 206. The changeover switch 205
If the supplied data is macroblock data of an I picture, it outputs the data as it is, and if it is data of a macroblock of another picture, the data supplied from the adder 206 is output. The changeover switch 205
Output data of the selection switch 21 that can be sequentially switched
4 is sequentially sent to and stored in the frame memories 210 to 213, and is used for image reproduction and display. That is, the data stored in the frame memories 210 to 213 is used for generating the predictive image data of the image data (P or B picture data) input later to the adder 206.

The reading of the frame memories 210 to 213 is controlled by the memory reading circuits 217 and 215, and the data read from the frame memories 210 to 213 is input to the corresponding selected terminals of the selection switches 207 to 209, respectively. Sent. This selection switch 207
The switches 209 to 209 are also switched according to the type of macroblock to be processed similarly to the switches 205 and 214.

Here, the outputs of the selection switches 208 and 209 are sent to the half pixel processing circuits 216 and 218 via the memory reading circuits 215 and 217, and the half pixel processing for halving the number of pixels is performed here. After being broken
It is sent to the corresponding selected terminal of the adder 219 or the selection switch 220. The output of the adder 219 is also the selection switch
Sent to 20 corresponding selected terminals. The output from the selection switch 220 is sent to the other switched terminal of the changeover switch 221 in which "0" is supplied to one switched terminal. The changeover switch 221 is changed over for each macroblock according to the picture type, and is switched to one of the switched terminals for an I picture and to the other switched terminal of another picture. The output of the changeover switch 221 is sent to the adder 206.

The output of the selection switch 207 is
The display control circuit 2 becomes the restored image data.
Sent to 22. The output from the display control circuit 222 is sent from the terminal 223 as an output video signal to the subsequent structure.

Further, the control sequencer 300 receives the error recovery bit from the variable length code decoding circuit 202 and receives the respective switches 205, 207 to 209, 21.
By performing the switching control of 4, 220 and 221, an error recovery process described later is performed.

By the way, the information reproducing apparatus of the present embodiment reproduces a disc when information compressed and encoded in the MPEG format is recorded on a recording medium such as a so-called compact disc.

Therefore, the data read from the disc may have an error. Thus M
If an error occurs in the decoding sequence of the playback device due to a read error in the data read from the disc in which the moving image bit stream compressed and encoded in the PEG format is recorded, the image is deteriorated.

Therefore, in the information reproducing apparatus of the present embodiment, even if a reproduction error occurs due to an error in reading data from the disc, deterioration of the image is suppressed as much as possible.
It is designed to be able to return to normal operation.

Hereinafter, in the information reproducing apparatus of this embodiment,
A method will be described in which even if there is an error in the read data, the recovery is performed by itself and the deterioration of the image quality due to the error is suppressed as much as possible to proceed with decoding.

In the apparatus of this embodiment, error recovery of the decoding sequence due to an error in the bit stream is performed by the control sequencer 300 by the following method.

First, in the control sequencer 300, when the error recovery bit generated by the variable length code decoding circuit 202 is 0, no error recovery is performed.

The error recovery in each layer is shown in FIG.
And according to the flowchart of FIG.

First, in FIG. 2, in step S500, it is determined whether or not there is a coefficient decoding error which is an error that occurs during the decoding of the variable length code. When it is determined as no, the determination is repeated, and when it is determined as yes, the process proceeds to step S501.

In step S501, the end of
A block (end of block) is transmitted, and step S502
In, the error is brought to the level of the macroblock layer (a macroblock in which six blocks are collected). That is, in step S502, it is determined whether the error is an error in the macro block,
When the determination is NO, the determination is repeated, and when the determination is YES, the process proceeds to step S503.

In step S503, macro blocks after the macro block in which the error has occurred are treated as skip macro blocks.

Here, in the case of a block layer error in a macroblock, the following is performed. For example, when an error occurs during coefficient decoding in a macroblock (intra macroblock) of an I picture, a DC value (that is, an average value) is maintained in that macroblock. D when entering the next macroblock
Reset C. That is, for example, a DC coefficient is treated as a macroblock (intra macroblock) of an I picture in which no coefficient in the same macroblock exists after that block. Subsequent macro blocks are
Motion compensation is performed from the forward side with vector = (0,0). Further, for example, the AC coefficient is treated as a macroblock in which no coefficient in the same macroblock exists after that block. For the subsequent macroblocks, from the forward side in the case of I picture and P picture, from the backward side in the case of B picture, vector = (0,
Motion compensation is performed in 0).

If the error is in the macroblock layer, the following is done. For example, the address is incremented. That is, the following macroblocks including the macroblock are motion-compensated from the forward side in the case of I and P pictures and from the backward side in the case of B pictures with vector = (0,0). As will be described later, for example, the next slice start code (s
It is repeated up to the position indicated by (lice start code). Further, the vector after the macro block in which the error has occurred is set to 0, and thereafter the same as the above address increment. Further, in the case of the coded block pattern, it is treated that there is no coefficient after the macro block, and thereafter, the same as the above address increment.

In other words, the handling of skip macroblocks means that no coefficient is generated when inter-frame correlation is calculated, and other macroblocks are handled as they are. In addition, whether to use the previous macroblock or the subsequent macroblock as the macroblock to skip at this time,
Depending on the type of picture, for example, in the case of P picture, the one that is earlier in time is used. For example, in the example of FIG. 4, when an error occurs in the P9 picture,
The picture of P6 is used. On the other hand, if an error occurs in the B picture, the latter picture is used. For example, if an error occurs in the picture of B11, it is taken from the picture of P9. When an error occurs in an I picture, the previous picture should not exist, but the signals handled in this embodiment are a series of video signals, and are therefore taken from the previous P picture.

Here, when the macro block is filled in after the error as the macro block handling, it is filled until the next start code is found. At this time, there are several types of start codes as described above,
In step S504, the slice start code is searched, for example. That is, it is determined whether the error is within the slice layer. If it is determined in step S504 that there is no slice start code, the process proceeds to step S505. On the other hand, when it is determined in step S504 that there is a slice start code, the process proceeds to step S506.

In step S506, the position designated by the slice start code (Slice start code) (S
x, Sy) and the current decoding position (Rx, Ry) are compared, and the decoding position of the macroblock until now is larger than the position (Sx, Sy) specified by the slice start code (slicestart code). Ba ((Rx, R
y)> (Sx, Sy)) The procedure returns to step S504, and the next slice start code (slice start cod
e) is searched for, and otherwise proceeds to step S507.

In step S507, (Rx, R
It is treated as a skip macroblock until y) = (Sx, Sy). That is, until the vertical position indicated by the slice start code, I,
Motion compensation is performed from the forward side in the case of a P picture and from the backward side in the case of a B picture with a vector = (0,0).

Thereafter, the process returns in step S507. That is, it returns from the head of the slice layer. By thus returning from the head of the slice layer, the horizontal skip is performed by the address increment of the macroblock. In other words, step S
In the flow of 504, step S506, and step S507, when the slice start code (slice start code) is found, the slice start code (s
(Slice start code) fills the previous data with the skip macroblock up to the position immediately before the position indicated by it.
Then, in step S508, normal decoding is resumed.

When it is determined in step S504 that there is no slice start code, in step S505, a process of skipping to the last macroblock is performed. That is, since the slice start code (slice start code) only needs to be included once for each image, it usually exists at the beginning and therefore does not exist at the time of error occurrence. As in step S513 of 3, the last macro block is skipped and filled.

Further, in step S504,
The slice start code (slice start code) is not found, and the picture start code (picture sta
rt code) and group start code (group start
code), sequence start code (sequence star)
t code) etc., as shown in Fig. 3,
Motion compensation is performed up to the end of the picture by the method described in the block layer and macroblock layer. After that, processing is performed according to the start code encountered.

Next, the flow of error recovery in the case of an error in another layer will be described with reference to FIG. Here, as the error of the other layer, the error of the picture layer is
The error in the case of the group layer error or the sequence layer error is either the error of the start code itself or the error of the marker bit. In addition,
After the error occurs, the next start code is searched for, but the user data start code (user data start
code), extension start code (extens
Ion start code) and other codes are skipped because the layers cannot be limited.

In FIG. 3, step S of FIG.
After skipping to the last macroblock in 505, or when the error is a picture layer error in step S510, a group layer error in step S511, or a sequence layer error in step S512, the following processing is performed.

First, in order to determine whether or not there is an error in the sequence layer, it is determined in step S514 whether or not there is the sequence start code (sequence start code). If YES is determined, step S51 is performed.
In step 8, the sequence layer is restored, and if the result is NO, the process proceeds to step S515.

In step S515, it is determined whether or not it is the group start code (group start code). If YES is determined, the group layer is restored in step S519, and if NO is determined, the step is performed. Proceed to S516.

In step S516, it is determined whether or not the picture start code is the picture start code. If YES is determined, the picture layer is restored in step S520, and if NO is determined in step S520. Proceed to S517.

In step S517, the sequence
If it is determined to be an end code (sequence end code), and if YES is determined, the sequence end is restored in step S521, and if NO is determined,
It proceeds to step S522.

In step S522, the next start code is searched for, and the flow returns to step S514.

[0077]

In the information reproducing apparatus of the present invention, if an error of each layer information occurs when the information recording medium in which a predetermined moving picture sequence composed of a plurality of layer information is recorded is reproduced. Since the error recovery is performed according to each layer, even if a reproduction error occurs due to an information reading error from the information recording medium, the deterioration of the image is suppressed as much as possible and the normal operation can be resumed.

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a configuration of a main part of an information reproducing apparatus according to an embodiment of the present invention.

FIG. 2 is a flowchart showing the first half of the flow of error recovery in the apparatus of this embodiment.

FIG. 3 is a flowchart showing the latter half of the flow of error recovery in the device of this embodiment.

FIG. 4 is a diagram for explaining the relationship between inter-frame correlation and picture type in the MPEG format.

FIG. 5 is a diagram for explaining a hierarchical structure in the MPEG format.

[Explanation of symbols]

 201 bit stream buffer 202 variable length code decoding circuit 203 inverse quantization circuit 204 inverse DCT circuit 205,221 changeover switch 206,219 adder 207-209,214 selection switch 210-213 frame memory 215,217 memory read circuit 216 , 218 Half-pixel processing circuit 222 Display control circuit 300 Control sequencer

Claims (7)

[Claims] 1. An information reproducing apparatus for reproducing an information recording medium in which a predetermined moving picture sequence composed of a plurality of layer information is recorded, wherein the error of each layer information is recovered according to each layer. An information reproducing apparatus having means. 2. The error recovery means averages the second layer information composed of a plurality of the first layer information, for the error in the first layer information which is the lowermost layer among the plurality of layer information. The information reproducing apparatus according to claim 1, further comprising first error recovery means for performing error recovery by using a value. 3. The error recovering means selects an error from a plurality of second layer information regarding an error in a second layer information including a plurality of first layer information which is a lowermost layer among the plurality of layer information. The second error recovery in which error recovery is performed by replacing information up to the next start position of the third layer information or the last position of the image including the second layer information with the information of the image preceding or succeeding in time. 3. The information reproducing apparatus according to claim 1, further comprising means. 4. The error recovering means selects an error from a plurality of second layer information regarding an error in the second layer information including a plurality of first layer information which is the lowest layer among the plurality of layer information. A second error recovery means for performing error recovery by replacing with predetermined information up to the next start position of the third hierarchy information or the last position of the image including the second hierarchy information. The information reproducing apparatus according to claim 1 or 2. 5. The error recovering means selects an error from a plurality of second layer information regarding an error in a second layer information including a plurality of first layer information which is a lowermost layer among the plurality of layer information. It is characterized by further comprising second error recovery means for performing error recovery by deleting information up to the next start position of the third hierarchy information or the last position of the image including the second hierarchy information. The information reproducing apparatus according to claim 1. 6. The error recovery means, regarding an error in the second layer information composed of a plurality of the first layer information which is the lowest layer among the plurality of layer information, a plurality of the second layer information. 3. The information reproducing apparatus according to claim 1, further comprising a second error recovering unit that recovers an error by returning to the head position of the third layer information consisting of. 7. The error recovery means is higher than the third layer information composed of a plurality of second layer information composed of a plurality of lowest layer first layer information among the plurality of layer information. For errors in layer information, skip to the start position of the next higher layer information and perform error recovery.
7. The information reproducing apparatus according to any one of claims 1 to 6, further comprising: an error recovery unit.