JPH06276482A - Picture signal coding method, coder, decoding method and decoder - Google Patents

Abstract

PURPOSE:To reduce number of bits of a variable length code produced at decod ing by adding a flag used to discriminate whether or not sliced data consist of a macro block subject to in-picture coding for each slicing to a bit stream. CONSTITUTION:A coded motion picture is inputted from a picture input terminal 110. The inputted picture signal is fed to a field memory group 111, from which an object block picture signal S1 being an object of coding at present is fed to a hybrid coder 112. The hybrid coder 112 executes hybrid coding in combination with motion compensation prediction coding and transformation coding such as DCT. Data S2 outputted from the hybrid coder 112 are subject to variable length coding such as Huffman coding at a VLC (variable length coding) device 113, the data are stored in a buffer memory 114 and sent at a predetermined transmission rate as a bet stream from an output terminal 115.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an information recording apparatus and an information reproducing apparatus for compressing moving image data by using a storage system recording medium such as an optical disk or a magnetic tape.

[0002]

2. Description of the Related Art Recently, in a so-called signal transmission system for transmitting video signals and audio signals to a remote place, such as a video conference system and a video telephone system,
In order to use the transmission path efficiently, it has been attempted to improve the transmission efficiency of information by encoding video signals and audio signals.

In particular, since moving image data has an extremely large amount of information, when this information is recorded for a long time, the video signal is highly efficient coded and recorded, and the recorded signal is efficiently read. A means for good decoding is indispensable, and in order to meet such a demand, a high-efficiency coding method utilizing the correlation of video signals has been proposed. One of the high-efficiency coding methods is MPEG (Moving Picture Expert).
s Group) method.

This MPEG system first reduces the redundancy in the time axis direction by taking the difference between the image frames of the video signal by utilizing the inter-frame correlation, and then by using the line correlation, the discrete cosine is used. The video signal is efficiently coded by reducing the redundancy in the spatial axis direction by using processing such as conversion (DCT).

When interframe correlation is used, for example, FIG.
As shown in (A) of FIG. ₁, T₂, T₃To
And the frame images PC1, PC2, and PC3 are
When it occurs, the image of frame image PC1 and PC2
The difference between the image signals is calculated, and the image is displayed as shown in FIG.
The PC12 is generated and the frame image of FIG.
By calculating the difference between the image signals of PC2 and PC3,
The image PC 23 of (B) is generated. Usually adjacent in time
Since the frame image to be changed does not change so much,
The difference signal when calculating the difference between two frame images is small
It will be a small value.

That is, the image PC1 shown in FIG.
2, the frame images PC1 and P of FIG.
As a difference between the image signals of C2, the image PC1 of FIG.
4 is obtained as a difference between the image signals of the frame images PC2 and PC3 of FIG. 4A in the image PC23 shown in FIG. 4B. The signal of the portion of the image PC23 of (B) indicated by the diagonal lines in the figure is obtained. Therefore, if this difference signal is encoded, the code amount can be compressed.

However, since the original image cannot be restored by transmitting only the difference signal, the image of each frame is converted into an I picture (Intra-coded picture: intra-coded or intra-coded image). P picture (Pre
dictive-coded picture: Bi-directional iy predictive-coded picture:
The image signal is compressed and coded as one of the pictures (bidirectional predictive coded image).

That is, for example, as shown in FIGS. 5A and 5B, 1 from frame F1 to frame F17
An image signal of 7 frames is used as a group of pictures and is used as one unit of processing. Then, the image signal of the leading frame F1 is encoded as an I picture, the second frame F2 is processed as a B picture, and the third frame F3 is processed as a P picture. Hereinafter, the fourth and subsequent frames F4 to F17 are alternately processed as a B picture or a P picture.

As the image signal of the I picture, the image signal for one frame is transmitted as it is. On the other hand, as the image signal of the P picture, basically, as shown in FIG.
(A), the difference from the image signal of the I picture or P picture preceding it in time is transmitted as a code. Further, as the image signal of B picture,
Basically, as shown in FIG. 5B, a difference from the average value of both the temporally preceding frame and the temporally following frame is obtained, and the difference is encoded and transmitted.

FIGS. 6A and 6B show the principle of the method of encoding a moving image signal in this way.
Note that FIG. 6A schematically shows frame data of a moving image signal, and FIG. 6B schematically shows frame data to be transmitted. As shown in FIG. 6, since the first frame F1 is processed as an I picture, that is, a non-interpolation frame, it is directly transmitted to the transmission path as transmission data F1X (transmission non-interpolation frame data) (intra-picture coding). . On the other hand, since the second frame F2 is processed as a B picture, that is, an interpolation frame, the frame F1 preceding in time and the frame F3 following in time (a non-interpolation frame of inter-frame coding) ) Is calculated, and the difference is transmitted as transmission data (transmission interpolation frame data) F2X.

However, there are four types of processing as the B picture, which will be described in more detail. In the first process, the data of the original frame F2 is converted into an arrow SP with a broken line in the figure.
As shown by 1, the data is transmitted as it is as the transmission data F2X (intra-picture coding), and the same processing as in the I picture is performed. The second process is to calculate a difference from the frame F3 that is temporally following and transmit the difference as indicated by a dashed arrow SP2 in the figure (backward predictive coding). The third process is the dashed arrow S in the figure.
As indicated by P3, the difference from the frame F1 preceding in time is transmitted (forward predictive coding). Further, in the fourth processing, as shown by a broken line arrow SP4 in the figure, a difference between the temporally preceding frame F1 and the average value of the following frame F3 is generated, and this difference is transmitted data F
It is transmitted as 2X (bidirectional predictive coding).

Of these four methods, the method that minimizes the amount of transmitted data is adopted.

When transmitting the difference data, the motion vector x1 between the image of the frame for which the difference is to be calculated (predicted image) (the motion between the frames F1 and F2 in the case of forward predictive coding). Vector) or motion vector x2 (frames F3 and F in the case of backward prediction coding)
2), or motion vectors x1 and x
Both of the two (for bidirectional prediction) are transmitted with the difference data.

A frame F3 (non-interpolation frame for inter-frame coding) of a P picture has a temporally preceding frame F1 as a prediction image and a difference signal (shown by a broken line arrow SP3) from the frame F1. Motion vector x3
Is calculated and transmitted as transmission data F3X (forward predictive coding). Alternatively, the original frame F3
Is transmitted as it is as transmission data F3X (indicated by a dashed arrow SP1) (intra-picture encoding). In this P picture, which method is used for transmission is
Similar to the case of B picture, the one with less transmission data is selected.

The B-picture frame F4 and the P-picture frame F5 are processed in the same manner as described above, and the transmission data F4X, F5X, the motion vectors x4, x5, x6.
Etc. are obtained.

FIG. 7 shows an example of the configuration of an apparatus which encodes and transmits a moving image signal based on the above-mentioned principle, and decodes the encoded moving image signal. The encoding device 1 is configured to encode the input video signal, transmit it to the recording medium 3 as a transmission path, and record it. Then, the decoding device 2 reproduces the signal recorded on the recording medium 3, decodes the signal, and outputs the decoded signal.

First, in the encoding device 1, the video signal VD input via the input terminal 10 is processed by the preprocessing circuit 11.
To the luminance and chrominance signals (in this example,
Color difference signals) are separated and A / D converted by A / D (analog / digital) converters 12 and 13, respectively. A /
The video signal converted into a digital signal by A / D conversion by the D converters 12 and 13 is sent to and stored in the frame memory 14. In the frame memory 14, the luminance signal is stored in the luminance signal frame memory 15, and the color difference signal is stored in the color difference signal frame memory 16, respectively.

Next, the format conversion circuit 17 converts the frame format signal stored in the frame memory 14 into a block format signal. That is,
As shown in FIG. 8A, in the video signal stored in the frame memory 14, H dot lines are V lines per line.
It is the data in the frame format in which lines are collected. The format conversion circuit 17 divides this 1-frame signal into N slices in units of 16 lines. Then, each slice is divided into M macroblocks, as shown in FIG. As shown in (C) of FIG. 8, each macroblock is composed of luminance signals corresponding to 16 × 16 pixels (dots), and this luminance signal is, as shown in (C) of FIG. 8x more
The blocks are divided into blocks Y [1] to Y [4] in units of 8 dots. Then, the luminance signal of 16 × 16 dots includes a Cb signal of 8 × 8 dots and a Cr signal of 8 × 8 dots.
The signals are matched.

The data converted into the block format as described above is supplied from the format conversion circuit 17 to the encoder 18, where it is encoded. The details will be described later with reference to FIG.

The signal encoded by the encoder 18 is output to the transmission path as a bit stream and recorded on the recording medium 3, for example. The data reproduced from the recording medium 3 is supplied to the decoder 31 of the decoding device 2 and decoded (decoded). Details of the decoder 31 will be described later with reference to FIG.

The data decoded by the decoder 31 is input to the format conversion circuit 32 and converted from the block format to the frame format. The luminance signal of this frame format is stored in the luminance signal frame memory 34 of the frame memory 33.
Is sent to and stored in the color difference signal frame memory 35. The luminance signal and the color difference signal read from the luminance signal frame memory 34 and the color difference signal frame memory 35 are D / A converted by the D / A converters 36 and 37, respectively, and supplied to the post-processing circuit 38, which performs the post-processing. It is synthesized in the circuit 38. This output video signal is
It is output from the output terminal 30 to a display (not shown) such as a CRT and is displayed.

Next, a configuration example of the encoder 18 will be described with reference to FIG.

First, the image data to be encoded, which is supplied through the input terminal 49, is input to the motion vector detection circuit 50 in units of the macro blocks. The motion vector detection circuit 50 converts the image data of each frame into an I-picture, according to a preset predetermined sequence.
It is processed as a P picture or a B picture. Here, the images of each frame that are sequentially input are
Which of I, P, and B pictures is to be processed is predetermined (for example, as shown in FIG. 5, the group of pictures composed of frames F1 to F17 is I, B, P, or B, P, ... B, P).

The image data of the frame to be processed as the I picture (for example, the frame F1) is transferred from the motion vector detection circuit 50 to the front original image portion 51a of the frame memory 51, stored therein, and processed as the B picture. Image data of a frame (for example, frame F2) to be stored in the original image portion (reference original image portion) 51b is stored, and image data of a frame (for example, frame F3) processed as a P picture is rearward original image portion. It is transferred to 51c and stored.

At the next timing, B
When an image of a frame to be processed as a picture (for example, the frame F4) or a P picture (for example, frame F5) is input, the first P picture (frame F3) stored in the backward original image portion 51c until then is input. The image data is transferred to and stored in the rear original image 51c.

At the next timing, B
When an image of a frame to be processed as a picture (for example, the frame F4) or a P picture (for example, frame F5) is input, the first P picture (frame F3) stored in the backward original image portion 51c until then is input. The image data is transferred to the front original image portion 51a, and the image data of the next B picture (frame F4) is transferred to the original image portion 51b.
Is stored (overwritten) in the next P picture (frame F
The image data of 5) is stored (overwritten) in the rear original image portion 51c. Such an operation is sequentially repeated.

The signal of each picture stored in the frame memory 51 is read therefrom, and the prediction mode switching circuit 52 performs frame prediction mode processing or field prediction mode processing. Furthermore, under the control of the prediction determination circuit 54, in the calculation unit 53,
Intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction is performed. Which of these processes is to be performed is determined in accordance with the prediction error signal (the difference between the reference image to be processed and the predicted image for this). Therefore, the motion vector detection circuit 50 generates the sum of absolute values (or the sum of squares) of the prediction error signal used for this determination.

Here, the frame prediction mode and field prediction mode in the prediction mode switching circuit 52 will be described.

When the frame prediction mode is set, the prediction mode switching circuit 52 supplies the four luminance blocks Y supplied from the motion vector detection circuit 50.
[1] to Y [4] are directly output to the arithmetic unit 53 in the subsequent stage. That is, in this case, as shown in FIG. 10A, the data of the odd field lines and the data of the even field lines are mixed in each luminance block. The solid lines in each macroblock of FIG. 10 represent the data of the odd field lines (the first field lines), and the broken lines represent the data of the even field lines (the second field lines). (A) and (b) show units of motion compensation.
In the frame prediction mode, prediction is performed in units of four luminance blocks (macro blocks), and one motion vector is associated with each of the four luminance blocks.

On the other hand, the prediction mode switching circuit 5
2 corresponds to FIG. 10 when the field prediction mode is set.
The signal input from the motion vector detection circuit 50 in the configuration shown in (A) of FIG. 10 is converted into the luminance blocks Y [1] and Y [2] among the four luminance blocks as shown in (B) of FIG.
Is composed only of dots of lines in odd fields, and the other two luminance blocks Y [3] and Y [4]
Is composed of the data of the lines of the even fields and is output to the arithmetic unit 53. In this case, one motion vector corresponds to the two luminance blocks Y [1] and Y [2], and the other two luminance blocks Y
Another motion vector is associated with [3] and Y [4].

Describing according to the configuration of FIG. 9, the motion vector detection circuit 50 calculates the sum of absolute values of prediction errors in the frame prediction mode and the sum of absolute values of prediction errors in the field prediction mode into the prediction mode switching circuit 52. Output to. The prediction mode switching circuit 52 compares the absolute value sums of the prediction errors in the frame prediction mode and the field prediction mode, performs the above-described processing corresponding to the prediction mode having the smaller value, and outputs the data to the calculation unit 53.

However, such processing is actually performed by the motion vector detection circuit 50. That is, the motion vector detection circuit 50 outputs a signal having a configuration corresponding to the determined mode to the prediction mode switching circuit 52, and the prediction mode switching circuit 52 outputs the signal as it is to the arithmetic unit 53 in the subsequent stage.

In the frame prediction mode, the color-difference signal is supplied to the arithmetic unit 53 in a state where the data of the odd field lines and the data of the even field lines are mixed, as shown in FIG. Supplied. In the field prediction mode, as shown in FIG.
The upper half (4 lines) of each color difference block Cb, Cr is set as an odd field color difference signal corresponding to the luminance blocks Y [1], Y [2], and the lower half (4 lines) is the luminance block Y [3]. ], Y [4] and color difference signals of even fields.

Further, the motion vector detection circuit 50 uses the prediction determination circuit 54 to predict the intra-image,
A sum of absolute values of prediction errors for determining whether to perform forward prediction, backward prediction, or bidirectional prediction is generated.

That is, the sum ΣAij of the signals Aij of the macroblocks of the reference image is used as the sum of the absolute values of the prediction errors of the intra-picture prediction.
Of the absolute value | ΣAij | of the macroblock signal and the sum Σ | Aij | of the absolute value | Aij | of the macroblock signal Aij. Also, as the sum of absolute values of prediction errors in forward prediction, the sum Σ of absolute values | Aij-Bij | of the difference (Aij-Bij) between the signal Aij of the macroblock of the reference image and the signal Bij of the macroblock of the predicted image.
| Aij-Bij | is calculated. Further, the sum of absolute values of the prediction errors of the backward prediction and the bidirectional prediction is also obtained in the same manner as in the case of forward prediction (the predicted image is changed to a predicted image different from that in forward prediction).

The sum of these absolute values is supplied to the prediction determination circuit 54. The prediction determination circuit 54 selects the smallest sum of absolute values of prediction errors of forward prediction, backward prediction, and bidirectional prediction as the sum of absolute values of prediction errors of inter prediction. Further, the sum of the absolute values of the prediction errors of the inter prediction and the sum of the absolute values of the prediction errors of the intra-picture prediction are compared, the smaller one is selected, and the mode corresponding to the selected sum of the absolute values is set as the prediction mode. select. That is,
If the sum of absolute values of prediction errors in intra-picture prediction is smaller, the intra-picture prediction mode is set. If the sum of absolute values of prediction errors in inter prediction is smaller, the mode in which the corresponding sum of absolute values is the smallest is set among the forward prediction, backward prediction, and bidirectional prediction modes.

In this way, the motion vector detection circuit 50
Has a configuration as shown in FIG. 10 in which the signal of the macroblock of the reference image corresponds to the mode selected by the prediction mode switching circuit 52 among the frame or field prediction modes, and is transmitted via the prediction mode switching circuit 52. A motion vector between the prediction image and the reference image corresponding to the prediction mode selected by the prediction determination circuit 54, out of the four prediction modes, is detected while being supplied to the calculation unit 53, and a variable length coding circuit described later is described. 58 and motion compensation circuit 64
Output to. As described above, the motion vector that minimizes the sum of the absolute values of the corresponding prediction errors is selected.

When the motion vector detection circuit 50 is reading the image data of the I picture from the front original image portion 51a, the prediction determination circuit 54 uses the intra-frame (image) prediction mode (the mode in which motion compensation is not performed) as the prediction mode. ) Is set, and the switch 53d of the calculation unit 53 is switched to the contact a side. As a result, the image data of the I picture is DCT
It is input to the mode switching circuit 55.

The DCT mode switching circuit 55, as shown in FIG. 11A or 11B, is a state in which the data of four luminance blocks are mixed with the lines of the odd field and the lines of the even field (frame). Either the DCT mode) or the separated state (field DCT mode) is output to the DCT circuit 56. That is, the DCT mode switching circuit 55 compares the coding efficiency in the case where the data of the odd field and the even field are mixed and is subjected to the DCT processing with the coding efficiency in the case where the DCT processing is performed in the separated state, and the coding efficiency is compared. Choose a good mode for.

For example, as shown in FIG. 11A, the input signal has a structure in which lines of odd fields and even fields are mixed, and signals of lines of odd fields and lines of even fields which are vertically adjacent to each other are arranged. The difference between the signals of is calculated, and the sum (or sum of squares) of the absolute values is calculated.
Ask for. Further, as shown in FIG. 11B, the input signal has a structure in which the lines of the odd field and the even field are separated, and the difference between the signals of the lines of the odd fields vertically adjacent to each other and the The difference between the signals on the lines is calculated, and the sum (or sum of squares) of the absolute values of the respective lines is calculated. Furthermore, comparing both (sum of absolute values),
Set the DCT mode corresponding to the smaller value. That is, if the former is smaller, set the frame DCT mode,
If the latter is smaller, the field DCT mode is set. Then, the data having the configuration corresponding to the selected DCT mode is output to the DCT circuit 56, and the DCT flag indicating the selected DCT mode is output to the variable length coding circuit 58 and the motion compensation circuit 64.

As is clear from a comparison between the prediction mode in the prediction mode switching circuit 52 (see FIG. 11) and the DCT mode in the DCT mode switching circuit 55 (see FIG. 12), with respect to the luminance block, each mode of the both. The data structures in are substantially the same.

When the frame prediction mode (a mode in which odd lines and even lines are mixed) is selected in the prediction mode switching circuit 52, the frame DCT mode (in which odd lines and even lines are mixed) is also selected in the DCT mode switching circuit 55. If the field prediction mode (mode in which the data in the odd field and the data in the even field are separated) is selected in the prediction mode switching circuit 52, the field in the DCT mode switching circuit 55 is high. There is a high possibility that the DCT mode (mode in which the data of the odd field and the data of the even field are separated) is selected.

However, this is not always the case, and the prediction mode switching circuit 52 determines the mode so that the sum of the absolute values of the prediction errors becomes smaller, and the DCT mode switching circuit 55 encodes the mode. The mode is determined so that the efficiency is good.

The I-picture image data output from the DCT mode switching circuit 55 is input to the DCT circuit 56, subjected to DCT (discrete cosine transform) processing, and converted into DCT coefficients. The DCT coefficient is input to the quantization circuit 57, quantized in a quantization step corresponding to the data storage amount (buffer storage amount) of the transmission buffer 59 in the subsequent stage, and then input to the variable length coding circuit 58. .

The variable length coding circuit 58 is a quantization circuit 57.
The image data (in this case, I picture data) supplied from the quantization circuit 57 corresponding to the supplied quantization step (scale) is, for example, Huffman (Huffm).
an) Converted into a variable length code such as code, and transmitted to the transmission buffer 59
Output to. In the variable-length coding circuit 58, the quantization step (scale) is set by the quantization circuit 57, and the prediction mode (whether intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction is set by the prediction determination circuit 54). , A motion vector from the motion vector detection circuit 50,
The prediction flag (which indicates whether the frame prediction mode or the field prediction mode is set) is set by the prediction mode switching circuit 52, and the DCT flag (either the frame DCT mode or the field DCT mode is set by the DCT mode switching circuit 55 is set. Has been input, and these are also variable length coded.

The transmission buffer 59 temporarily accumulates the input data, and quantizes the data corresponding to the accumulated amount in the quantizing circuit 57.
Output to. When the remaining amount of data increases to the allowable upper limit value, the transmission buffer 59 increases the quantization scale of the quantization circuit 57 by the quantization control signal,
The amount of quantized data is reduced. On the contrary, when the data remaining amount decreases to the allowable lower limit value, the transmission buffer 59 uses the quantization control signal to quantize circuit 57.
The data amount of the quantized data is increased by reducing the quantization scale of. In this way, overflow or underflow of the transmission buffer 59 is prevented. Then, the data accumulated in the transmission buffer 59 is
It is read at a predetermined timing, is output to the transmission path via the output terminal 69, and is recorded on the recording medium 3, for example.

On the other hand, the I picture data output from the quantization circuit 57 is input to the inverse quantization circuit 60 and inversely quantized in accordance with the quantization step supplied from the quantization circuit 57. The output of the inverse quantization circuit 60 is IDCT
After being input to the (inverse DCT) circuit 61 and subjected to inverse DCT processing, it is supplied to and stored in the forward predicted image portion 63a of the frame memory 63 via the calculator 62.

By the way, the motion vector detection circuit 50
The image data of each frame that is sequentially input is, for example, I, B, P, B, P, B as described above.
, Respectively, after processing the image data of the first input frame as an I picture, and before processing the image of the next input frame as a B picture, further input The image data of the selected frame is processed as a P picture. This is because the B picture is accompanied by backward prediction and cannot be decoded unless the P picture as a backward predicted image is prepared in advance.

Then, the motion vector detecting circuit 50 starts the processing of the image data of the P picture stored in the rear original image portion 51c after the processing of the I picture. Then, as in the case described above, the absolute value sum of the inter-frame difference (prediction error) in macroblock units is supplied from the motion vector detection circuit 50 to the prediction mode switching circuit 52 and the prediction determination circuit 54. Prediction mode switching circuit 52
And the prediction determination circuit 54 sets the frame / field prediction mode, or the prediction mode of intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction in accordance with the sum of the absolute values of the prediction errors of the macroblock of the P picture. To do.

When the intra-frame prediction mode is set, the arithmetic unit 53 switches the switch 53d to the contact a side as described above. Therefore, this data is similar to the I picture data in that the DCT mode switching circuit 55, DCT
It is transmitted to the transmission line via the circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59. Further, this data is supplied to and stored in the backward prediction image section 63b of the frame memory 63 via the inverse quantization circuit 60, the IDCT circuit 61, and the computing unit 62.

On the other hand, in the forward prediction mode, the switch 53
d is switched to the contact b, and the frame memory 6
The image data (in this case, an I-picture image) stored in the forward predictive image unit 63a of No. 3 is read out, and the motion compensation circuit 64 makes a motion corresponding to the motion vector output from the motion vector detection circuit 50. Will be compensated. That is, the motion compensation circuit 64, when the prediction determination circuit 54 commands the setting of the forward prediction mode, the forward prediction image unit 63.
The read address of a is shifted by an amount corresponding to the motion vector from the position corresponding to the position of the macro block currently output by the motion vector detection circuit 50, and the data is read to generate predicted image data.

The predicted image data output from the motion compensation circuit 64 is supplied to the calculator 53a. Calculator 53a
Subtracts the predicted image data corresponding to this macroblock supplied from the motion compensation circuit 64 from the data of the macroblock of the reference image supplied from the prediction mode switching circuit 52, and outputs the difference (prediction error). To do. This difference data is the DCT mode switching circuit 55, DC
T circuit 56, quantization circuit 57, variable length coding circuit 58,
It is transmitted to the transmission line via the transmission buffer 59. Also,
This difference data is stored in the inverse quantization circuit 60 and the IDCT circuit 6
It is locally decoded by 1 and input to the calculator 62.

The computing unit 62 also includes a computing unit 53a.
The same data as the predicted image data supplied to the computer is supplied. The calculator 62 adds the predicted image data output by the motion compensation circuit 64 to the difference data output by the IDCT circuit 61. As a result, the image data of the original (decoded) P picture is obtained. The image data of this P picture is stored in the backward prediction image portion 63b of the frame memory 63.
Are stored and stored in.

In this way, the motion vector detection circuit 50 executes the process of the B picture after the data of the I picture and the P picture are stored in the forward predicted image portion 63a and the backward predicted image portion 63b, respectively. The prediction mode switching circuit 52 and the prediction determination circuit 54 correspond to the magnitude of the sum of absolute values of inter-frame differences in macroblock units,
The frame / field mode is set, and the prediction mode is set to either the intra-frame prediction mode, the forward prediction mode, the backward prediction mode, or the bidirectional prediction mode.

As described above, in the intra-frame prediction mode or the forward prediction mode, the switch 53d is switched to the contact a or b. At this time, the same processing as in the P picture is performed and the data is transmitted. On the other hand, when the backward prediction mode or the bidirectional prediction mode is set, the switch 53d is switched to the contact c or d, respectively.

In the backward prediction mode in which the switch 53d is switched to the contact c, the image (in this case, P picture image) data stored in the backward predicted image portion 63b is read out and the motion compensation circuit 64 is read. Thus, motion compensation is performed corresponding to the motion vector output by the motion vector detection circuit 50. That is, when the prediction determination circuit 54 instructs the motion compensation circuit 64 to set the backward prediction mode,
The read address of the backward predicted image portion 63b is shifted from the position corresponding to the position of the macro block currently output by the motion vector detection circuit 50 by the amount corresponding to the motion vector, and the data is read to generate predicted image data.

The predicted image data output from the motion compensation circuit 64 is supplied to the calculator 53b. Calculator 53b
Subtracts the predicted image data supplied from the motion compensation circuit 64 from the data of the macroblock of the reference image supplied from the prediction mode switching circuit 52, and outputs the difference. This difference data is stored in the DCT mode switching circuit 5
5, the DCT circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59.

In the bidirectional prediction mode in which the switch 53d is switched to the contact point d, the image data (in this case, the I picture image) stored in the forward predicted image portion 63a and the backward predicted image portion 63b are stored. The image data (in this case, the image of the P picture) being read is read out, and the motion compensation circuit 64 causes the motion vector detection circuit 5
Motion compensation is performed according to the motion vector output by 0.
That is, the motion compensation circuit 64, when the bidirectional prediction mode setting is instructed by the prediction determination circuit 54, the motion vector detection circuit 50 now outputs the read addresses of the forward predicted image portion 63a and the backward predicted image portion 63b. The data is read out by shifting the amount corresponding to the motion vector (in this case, there are two for the forward prediction image and the backward prediction image) from the position corresponding to the position of the existing macroblock, and the prediction image data is generated. To do.

The predicted image data output from the motion compensation circuit 64 is supplied to the calculator 53c. Calculator 53c
Subtracts the average value of the predicted image data supplied from the motion compensation circuit 64 from the macroblock data of the reference image supplied from the motion vector detection circuit 50, and outputs the difference. This difference data is transmitted to the transmission line via the DCT mode switching circuit 55, the DCT circuit 56, the quantization circuit 57, the variable length coding circuit 58, and the transmission buffer 59.

The B picture image is not stored in the frame memory 63 because it is not used as a predicted image of another image.

In the frame memory 63, the forward predictive image portion 63a and the backward predictive image portion 63b are bank-switched as necessary, and a predetermined reference image
What is stored in one or the other can be switched and output as a forward prediction image or a backward prediction image.

In the above description, the description has been centered on the luminance block, but the same applies to the color difference block in FIG.
0 and the macro block shown in FIG. 11 is processed as a unit and transmitted. The motion vector used for processing the color difference block is obtained by halving the motion vector of the corresponding luminance block in each of the vertical direction and the horizontal direction.

Next, FIG. 12 is a block diagram showing the structure of an example of the decoder 31 shown in FIG. The encoded image data transmitted via the transmission path (recording medium 3) is received by a receiving circuit (not shown) or reproduced by a reproducing device.
After being temporarily stored in the reception buffer 81, it is supplied to the variable length decoding circuit 82 of the decoding circuit 90. The variable length decoding circuit 82 performs variable length decoding on the data supplied from the reception buffer 81, the motion vector, the prediction mode, the prediction flag and the DCT flag to the motion compensation circuit 87, and the quantization step to the dequantization circuit. And outputs the decoded image data to the inverse quantization circuit 83.

The inverse quantization circuit 83 is used in the variable length decoding circuit 8
The image data supplied from No. 2 is inversely quantized according to the quantization step supplied from the variable length decoding circuit 82, and output to the IDCT circuit 84. The data (DCT coefficient) output from the inverse quantization circuit 83 is the IDCT circuit 8
In step 4, inverse DCT processing is performed and the result is supplied to the calculator 85.

When the image data supplied from the IDCT circuit 84 is I-picture data, the data is output from the arithmetic unit 85 and input to the arithmetic unit 85 later (P or B-picture data). Is generated and supplied to the forward prediction image unit 86a of the frame memory 86 to be stored therein. Further, this data is output to the format conversion circuit 32 (FIG. 7).

When the image data supplied from the IDCT circuit 84 is P picture data in which the image data one frame before is the predicted image data and is the data in the forward prediction mode, the forward prediction of the frame memory 86 is performed. The image data of one frame before (image data of I picture) stored in the image portion 86a is read out, and the motion compensation circuit 8
At 7, motion compensation corresponding to the motion vector output from the variable length decoding circuit 82 is performed. Then, in the calculator 85, the image data (difference data) supplied from the IDCT circuit 84 is added and output. The added data, that is, the decoded P picture data is
In order to generate predictive image data of image data (B-picture or P-picture data) input later to the calculator 85, it is supplied and stored in the backward predictive image section 86b of the frame memory 86.

Even in the case of P-picture data, the intra-picture prediction mode data is stored in the backward-prediction image section 86b as it is without any special processing by the calculator 85, like the I-picture data. Since this P picture is an image to be displayed next to the next B picture, it is not yet output to the format conversion circuit 32 at this point (as described above, the P picture input after the B picture is Processed and transmitted prior to B-pictures).

When the image data supplied from the IDCT circuit 84 is B picture data, it is stored in the forward predicted image portion 86a of the frame memory 86 in accordance with the prediction mode supplied from the variable length decoding circuit 82. Has been I
The image data of the picture (in the case of the forward prediction mode), the image data of the P picture stored in the backward prediction image portion 86b (in the case of the backward prediction mode), or both image data (in the case of bidirectional prediction mode) The motion compensation circuit 87 reads out and performs motion compensation corresponding to the motion vector output from the variable length decoding circuit 82,
A predicted image is generated. However, when motion compensation is not required (in the case of the intra-picture prediction mode), the predicted picture is not generated.

The data thus motion-compensated by the motion compensating circuit 87 is sent to the calculator 85 for IDC.
It is added to the output of the T circuit 84. This addition output is output to the format conversion circuit 32. However, since this addition output is B picture data and is not used for generating a predicted image of another image, it is not stored in the frame memory 86.

After the B picture image is output, the P picture image data stored in the backward prediction image section 86b is read out, and the arithmetic unit 85 is passed through the motion compensation circuit 87.
Is supplied to. However, at this time, motion compensation is not performed.

The decoder 31 includes a prediction mode switching circuit 52 and a DCT in the encoder 18 of FIG.
Although the circuits corresponding to the mode switching circuit 55 are not shown, the processing corresponding to these circuits, that is, the configuration in which the signals of the lines in the odd field and the even field are separated is necessary for the original mixed configuration. The motion compensation circuit 87 executes the process of returning.

Although the processing of the luminance signal has been described above, the processing of the color difference signal is also performed in the same manner.
However, in this case, the motion vector used for the luminance signal is halved in the vertical and horizontal directions.

FIG. 13 shows the MPEG in the MPEG system.
The format of data of one image (picture) in one system is shown. Here, although the image unit is described as a frame, a field may be used as an image unit for an interlaced image.

The video sequence layer shown in FIG. 13 (a) is composed of one or a plurality of group of picture layers shown in FIG. 13 (b) having the same image size and image rate. This group of picture layer is as shown in (c) of FIG. 13, and is composed of one or a plurality of I pictures and 0 or a plurality of pictures other than I pictures, that is, P pictures and / or B pictures. Composed. The I picture, P picture, and B picture are classified according to the encoding method as described above. The picture layer is composed of at least one or a plurality of slice layers as shown in (d) of FIG.

The slice layer is composed of one or a plurality of macroblocks which are continuous in the scanning order within the picture shown in FIG. At the beginning of this slice, the first macroblock has data indicating its position in the image, and it is thought that the image data can be restored even if an error occurs. Therefore, the slice length and start position are arbitrary and can be changed according to the error state of the transmission path.

Further, each macroblock of the macroblock layer shown in FIG. 13 (f) has four luminance blocks adjacent to each other in the left, right, top and bottom when the image signal is a 4: 2: 0 component signal, for example. The color difference blocks Cb and Cr corresponding to the same position on the image are composed of a total of six blocks. The order of transmission of each block is Y0, Y1, Y2, Y3, Cb, Cr.
Is. The determination of which block to use in the motion compensation mode, whether to send a prediction error, or the like is made in units of this macroblock. This block layer is composed of, for example, 8 lines × 8 pixels adjacent to each other in luminance or color difference, and is, for example, D
CT (Discrete Cosine Transform) conversion is performed in this block unit.

Since the bit pattern of the start code added to the head of the slice is a unique code that is generated only in the bit stream and is prohibited from being generated in other bits, it is not possible to use it in the transmission path. When an error occurs, image data can be restored in slice units. This start code is represented by a 32-bit code. In hexadecimal notation, 24-bit "000" is displayed.
001 ”code and this 24-bit code,
It is a combination with an 8-bit code that identifies the type of start code.

Table 1 shows the type of each start code.

[0079]

[Table 1]

This start code is distinguished by the lower 8 bits in the 32-bit code, and its identification code is 1
It is a hexadecimal number and has a value from 00 to FF. here,
Lower 8 of "slice_start_codes" indicated by 32 bits
The bit represents the vertical position of the slice on the image.
For example, when the vertical size of the image frame of one image is 480 lines, the vertical position of the slice is 1 to 30 (= 480/16).
Takes a value up to. In the MPEG1 system, the value of the vertical position of this slice is 1 to 175 (0 in hexadecimal notation).
1 to AF) are prepared, it is possible to display the vertical position of the slice up to 2800 (= 175 × 16) lines in the vertical size of the image frame.

The value of the vertical position of the slice serves as an identification code for identifying whether or not the received start code is a slice in the image decoding apparatus. That is, in the image decoding apparatus, when the lower 8 bits of the received start code are 01 to AF in hexadecimal notation, it is possible to recognize that the information that follows is of the slice layer.

[0082]

By the way, as shown in FIG. 14, the unit area for intra-picture coding is not the entire screen such as a frame or field, but a smaller area may be used as the unit area. is there. In this case, the area is subjected to intra-frame or intra-field coding and intra-frame or intra-field decoding. At this time, when this area exists in the P picture or the B picture, it is necessary to use the encoding and decoding method according to the P picture or the B picture.

Therefore, the area in which the intra-frame or intra-field encoding and decoding method needs to be used according to the P picture or the B picture can be regarded as a part of the I picture substantially. ,
Since the encoding / decoding method for the I picture cannot be used and the encoding / decoding method for the P picture or B picture is used, redundant encoding / decoding is performed.

In the MPEG system, a special code is set to synchronize slices. MP
In the EG1 system, this code is defined as a start code as shown in Table 1. Since the position of this start code is determined to be a position of every 8 bits for easy synchronization, an arbitrary number of 0's can be inserted before this start code. Therefore, to prevent the buffer from becoming empty, slice 1 start Since a very large number of 0's are inserted before the slice start code indicated by codes, conventionally, it is prohibited to end the last 8 bits of the slice start code with all 0s, and consecutive 0s are 8 bits. There is a method of determining whether or not the 8 bits are included in the slice start code by detecting every 8 bits.

However, according to the method as described above, it is possible to judge whether or not the detected continuous 8-bit code is included in the slice start code. Since it is not possible to specify whether it is a part, it is not possible to specify the start position of the slice start code.

Furthermore, since intra-picture predictive coding is not performed in the area where the above-mentioned intra-picture coding, that is, intra-frame or intra-field coding, is performed, in principle, only image data within a frame or within a field. You should be able to decrypt with. However, the above MPE
In the G1 system, the above-mentioned inter-picture predictive coding is not performed, and the information necessary for decoding the image data of the area in which the intra-frame or intra-field coding is performed does not exist in the header of the area. Therefore, it is not possible to decode the image data in the area in which the intra-frame or intra-field coding is performed.

[0087]

According to the present invention, an image signal coding including at least an intra-picture coding mode is selected as a coding mode selected when coding image signal data in units of a macroblock composed of a plurality of pixels. In the method, a flag for determining whether or not the intra-picture coding mode is set is added to each slice formed by arranging a plurality of the macroblocks.

The flag is added by using the least significant bit of the slice start code indicating the head of the slice.

Further, each picture which is one image is classified into a plurality of picture types according to a coding method, and the picture types include at least an intra-picture coded picture and an inter-picture predictive coded picture, In the intra-picture coded picture, the macroblock type representing the information regarding the coding for each macroblock is coded by a predetermined variable length code, and in the inter-picture predictive coded picture, the macroblock type is coded by another variable length code. In the image signal coding method, the whole macroblock type in the slice shown as the intra-picture coding is coded by the predetermined variable length code, and for each slice to which the flag is added, the slice is It is characterized by adding information for decoding.

An image signal coding apparatus that uses an image signal coding method including at least an intra-picture coding mode as a coding mode selected when coding image signal data in units of macroblocks composed of a plurality of pixels. In the above, a control unit for adding a flag for determining whether or not the intra-picture coding mode is set is provided for each slice formed by arranging the plurality of macroblocks.

Further, in the image signal coding method including at least the intra-picture coding mode as the coding mode selected when the image signal data is coded in the macro block unit composed of a plurality of pixels, For each slice formed by arranging multiple images, intra-picture decoding is performed for each slice in which a flag for determining whether to use the intra-picture coding mode is detected, and the maximum of the slice start code indicating the beginning of the slice is The flag is added by using the lower bits, and when detecting a series of zeros that continuously exist before the slice start code, the zeros are detected every 8 bits to detect the beginning of the slice start code. For each slice to which the above flag has been detected and added, decoding is performed using information for decoding the slice. To.

Further, the image signal decoding using the image signal encoding method including at least the intra-image encoding mode as the encoding mode selected when encoding the image signal data in units of macroblocks composed of a plurality of pixels The apparatus is characterized by performing intra-picture decoding for each slice formed by arranging a plurality of the macro blocks, in units of slices in which a flag for determining whether or not the intra-picture coding mode is set is detected. To do.

Here, the predetermined variable length code means a variable length coding code indicating the macroblock type of I picture, and the other variable length code means the macroblock type of P picture and B picture. It shows the variable length code shown.

[0094]

In the present invention, it is possible to reduce the number of bits of the generated variable length code by using the flag for determining whether or not the frame or field is coded.

Since the flag is added to the least significant bit of the slice start code, the start position of the slice start code can be specified.

Furthermore, by using the above flag,
For a slice that has been intra-coded, the image data of the slice that has been intra-coded can be decoded only with the information added in the slice header.

[0097]

DESCRIPTION OF THE PREFERRED EMBODIMENTS First, a preferred embodiment of the image signal coding method of the present invention will be described. A flag for determining whether or not the intra-picture coding mode is set is added to each slice formed by arranging a plurality of macroblocks, and coding is performed in the intra-picture coding mode existing in the inter-picture coding mode by the I picture. The number of bits of the variable length code of the converted macroblock is reduced.

Also, the above flag is set to structure As a flag, it is shown by using the least significant bit of the slice start code that indicates the beginning of the slice, and the above flag structure The start position of the slice start code is detected by flag.

In addition, the slice header is set in the slice header.
The entire frame is intra-coded, i.e.
When coded with intra-field coding, for example, video
Intra in sequence header quantizer matrix, pic
Picture in Cha layer structure, Interlaced progre
ssive flag, Intra dc precision and Qscale type
Etc. are duplicated in the slice layer. After this, the above encoding
The above flag struct
ure The slice indicated by flag is intra-coded
If the slice layer is
Even if there is no upper layer data,
The I-picture is encoded based on the information of the group.
A detailed description of each flag will be given later.

Next, FIG. 1 shows a block diagram of an embodiment of an encoding apparatus according to the present invention. The basic encoding method in the present invention is the same as the encoding method based on the MPEG method.

Information such as an image frame size for controlling the basic operation of the present encoding device, an output bit rate of encoded information, and a motion prediction / compensation method is stored in the memory 118. These pieces of information are output as the signal S25. The moving image to be encoded is input from the image input terminal 110. The input image signal is supplied to the field memory group 111. From the field memory group 111, the block pixel signal S1 to be currently encoded is supplied to the hybrid encoder 112.

In this hybrid encoder 112, motion compensation predictive coding and D
Hybrid that combines transform coding such as CT
d) Encode. The data S2 output from the hybrid encoder 112 is the VLC (variable length encoder) 1
At 13, variable-length coding such as Huffman coding is performed, and after being accumulated in the buffer memory 114, it is sent from the output terminal 15 as a bit stream at a constant transmission rate.

The above bitstream has 6 bits as described above.
It is composed of three layers, namely, a video sequence layer, a group of picture layer, a picture layer, a slice layer, a macroblock layer and a block layer. Among these layers are video sequence layer, group of picture layer, picture layer,
A start code indicating the start of each of the slice layers is added to the head of the slice layer, and then the header information is transmitted. The timing of transmitting each start code is the same as the video sequence start flag S2.
0, group of picture start flag S21, picture start flag S22, slice start flag S
It is when 23 was set up. The video sequence start flag S20, the group of picture start flag S21, and the picture start flag S22 among the above start flags are output from the picture counter 116,
The slice start flag S23 is output from the macroblock counter 117.

The picture counter 116 counts the number of the target images (pictures) currently read from the field memory group 111 and encoded and is synchronized with the signal S30 output. To do. Also,
When the coding of the video sequence layer is started in the picture counter 116, the picture counter 116 is reset, and at the same time, the video sequence start flag S20 is set. The picture start flag S22 is set to the picture counter 1
16 is set when receiving the signal S30, and the group of picture start flag S21 is a multiple of the number of pictures counted by the picture counter 116, that is, a predetermined group of picture length, that is, the number of pictures forming the group of picture. Is set up when it becomes. The group-of-picture length is usually, for example, 12 frames or 15 frames, and the loop-of-picture length information is stored in the memory 118 in which control information for encoding the image currently being encoded is stored. Remembered in.

The macroblock counter 117 counts the number of the target macroblocks currently read out from the field memory group 111 and encoded, in synchronization with the signal S31 outputted. . The macroblock counter 117 is reset when the signal S30 is received. Further, the slice start flag S23 is set to the macro block counter 117.
The slice length is a predetermined slice length,
That is, it is set to be a multiple of the number of macroblocks that make up a slice. This slice length can be changed according to the state of an error that occurs during transmission of the bit stream in the transmission path. Generally, the higher the probability of error during transmission, the shorter the slice length. The designated slice length at this time is stored in the memory 118.

Video sequence start flag S2
0, group of picture start flag S21, picture start flag S22, slice start flag S
When any one of the flags 23 is set, the above V
The LC (variable length coding) unit 113 outputs the start code of each layer. Then, the control information for encoding the data of each layer stored in the memory 118 is output from the VLC unit 113 as header information.

The details of the bitstream syntax when outputting the slice header will be described.
Table 2 shows the syntax of the slice header of the slice layer in this embodiment.

[0108]

[Table 2]

In this slice header, the vertical position of the slice on the image is transmitted. This slice vertical position is
It is calculated by the equation (1). slice _vertical_position = mb _address / mb_width +1. ． ． (1)

Mb_address in the equation (1) is the number counted by the macroblock counter 117. In the first macro block in the image, this mb
The value of _address is 0. In addition, mb_width is the number of macroblocks in a horizontal row of the image frame of the image. For example, when the horizontal size of the image frame is 720 pixels, mb_width
The value of width is 45 (= 720/16). The slice vertical position calculation circuit 119 inputs the value of the vertical position of the slice calculated by the equation (1) to the output format converter 120. In the output format converter 120, the value of the calculated vertical position of the slice is subjected to S26, which is the value of the vertical size of the image frame of the image, to perform the output format conversion as necessary.

Next, an image signal decoding device corresponding to the above-mentioned image signal encoding device will be described with reference to FIG.

The input bitstream signal from the input terminal 130 is stored in the buffer memory 131 and then inverted V
It is supplied to an LC (variable length coding) unit 132. As described above, this bit stream is composed of six layers, that is, a video sequence layer, a group of pictures layer, a picture layer, a slice layer, a macroblock layer, and a block layer. The inverse VLC unit 132 receives the start code indicating the start position at the beginning of each of the video sequence layer, the group of picture layer, the picture layer, and the slice layer, decodes the header information of each layer, and obtains the obtained image. The control information for decoding is stored in the memory 136.
These pieces of information are output as S104. After that, the header information that controls the image decoding process is received.

Here, a method of decoding the value of the vertical position on the image of the current slice, which is obtained when the slice header is decoded, will be described below.

The slice vertical position restoring unit 134 restores the slice vertical position value S70. The restoration method of this value S70 is performed by using the value S60 of the vertical size of the image frame
Depends on The vertical size value S60 of the image frame of this image is obtained when the picture header information is decoded, and is stored in the memory 13
6 is stored.

After the slice layer, the macroblock layer data signal S80 is received and supplied to the hybrid decoder 133. This hybrid decoder 13
3 is a high-efficiency coding method for moving images, a hybrid (h) that combines motion compensation and transform coding such as inverse DCT.
ybrid) Decrypt. The decoded macroblock layer data S81 is output from the output terminal 135.

As described above, the image data is restored from the bit stream data.

Next, a method of adding a flag for determining whether or not there is an intra-picture coded macroblock by intra-frame or intra-field coding will be described.

That is, the P pictures P2, P5,
The hatched area A in each frame of P8 and P11 is a part of the P picture in which the inter-picture predictive coding is to be performed, and areas composed of a plurality of macroblocks are dispersed on the screen. When this is present, a flag is newly provided to determine whether or not this intra-picture coded macroblock exists.

Here, the syntax of the MPEG system is hierarchical, but the lowest unit in which the synchronization code is used is a slice. For this reason, in this embodiment, a flag is provided in the slice header for detecting whether or not the intra-coded macroblock exists. For example, in the present embodiment, the slice is one column on the screen of the macroblock, and a flag indicating whether or not a certain slice is composed of intraframe-encoded macroblocks is provided.

For example, the P pictures P2 and P in FIG.
In the slice of the intra-picture coded area indicated by A in the frame of P5, P8, and P11, the intra-coded macroblock exists, and in the other slice indicated by B, the frame Since there is a macroblock that has not been intra-coded, a flag that distinguishes these two types of slices
Provide a Structure flag. The flag is set to 1 when the slice includes the intra-frame coded macroblock, and the flag is reset when the slice includes the non-frame-coded macroblock.

When the above flag is set to 1, even if this slice exists in a P picture or B picture, there is a macroblock which is intra-frame coded, so that it is a P picture or B picture. It is not necessary to have information on all the macroblock types prepared in 1., the type of macroblock in the I picture is sufficient. That is, the coding and decoding in the I picture can be applied only in the slice in which the flag is set to 1.

Tables 3, 4, and 5 show variable length coding tables for the macroblock types of the I picture, P picture, and B picture, respectively.

[0123]

[Table 3]

[0124]

[Table 4]

[0125]

[Table 5]

In Table 3, Table 4, and Table 5, each item of the designation of the quantum width for indicating the macroblock type, the forward motion vector, the backward motion vector, the coded block display, the intra-image vector, and the compatible macroblock is shown. Generates a variable length coded code for each macroblock in the above three types of pictures.

As shown in Tables 4 and 5, the type of the intra-frame coding macroblock in the P picture or the B picture is the variable length coding code "00011" unless the quantization width is specified. If the quantization width is specified, the variable length coding code is “000
It becomes 001 ".

However, the type of the macroblock in the I picture is "1" if the quantization width is not specified, and is "01" if the quantization width is specified. Therefore, in the encoding process, it is known in advance that the intra-frame encoding is performed. Therefore, if the encoding and the decoding in the I picture are applied, the variable length encoding code is 4 bits for each macro block type. The number of bits due to can be reduced.

The above-mentioned flag is introduced inside the syntax of the MPEG system as shown in Table 2, for example. In the image signal encoding apparatus of FIG. 1 according to the embodiment of the present invention, the flag of the image information storage memory 18 is set in advance for a slice to be intra-frame encoded, and the flag is written in the header of the slice. .

Also, when the input bitstream is decoded by the decoding apparatus of FIG. 2 according to the embodiment of the present invention, the above flag is used. First, the slice start code is detected. When this slice start code is detected, the predetermined position of the slice header is decoded and the above flag Structur
e Detect the flag. At this time, if this flag is set to 1, the bitstream following the slice header is decoded by the decoding method for the I picture until the slice header of the next slice is detected.

However, if the flag is 0, the bitstream following the slice header is decoded by the decoding method in the picture to which the slice belongs until the slice header of the next slice is detected. For example, the inverse VLC circuit 132 of the decoding device of FIG.
The contents of the flag decoded in (1) are set in the decoded information storage memory 136, and the decoding is performed using the information as the signal S104.

Next, a method for specifying the start position of the 32-bit slice start code will be described.

Here, the least significant bit of the slice start code is used as structure_flag. When comparing a slice start code according to the present invention with a conventional slice start code, sli indicating the vertical position of the slice
ce vertical Since the position starts from 1, it is theoretically not possible to represent it with a value of 0000 0000 0000 0000 0000 0001 0000 0001 in binary. Therefore, the code that takes the above value is prohibited.

Therefore, it is possible to specify that the continuous code of 0000 0001 is a code from 16 bits of the start code. On the contrary, the code that takes a value other than consecutive 0000 0001 is 2 of the slice start codes.
It can be specified that the code is from 4 bits. Therefore, when detecting every 8 bits, the start position of the start code can be specified from the content of the detected code, and the processing can be performed faster than in the conventional case.

Specifically, the detected codes are consecutive
If it is an 8-bit code of 0000 0001,
It can be seen that the next 8 bits following this 8-bit code indicate the type of start code. If the value of the continuous 8-bit code is other than 0000 0001, the 8-bit code itself indicates the type of start code.
The process can start from that point. A flowchart of this process is shown in FIG.

At step SP1 in FIG. 3, the continuous 8-bit code in the slice start code is read out,
In step SP2, it is determined whether or not all 8 bits of the read code are 0. If all 0s, the process proceeds to step SP3 to read the next continuous 8-bit code. If not all 0s, the process proceeds to step SP12 to analyze the above code as a variable length code, and then to analyze. It is determined whether or not it has ended.

The continuous 8-bit code read in step SP3 is also set to 0 in step SP4.
If it is not all 0, the process proceeds to step SP12 as described above, and the code is analyzed as a variable length code.

If it is determined in step SP4 that the read 8-bit codes are all 0, the process proceeds to step SP5, the next consecutive 8-bit code is read, and the code is read in step SP6. Are all 0 or not. If they are not all 0, the process proceeds to step SP12 as described above and the above code is analyzed as a variable length code.

When it is judged at step SP6 that all the read codes are 0, the routine proceeds to step SP7, where the next consecutive 8-bit code is skipped.
After this, the next consecutive 8-bit code may be the lower 8 bits of the slice start code, so
At step SP8, the next consecutive 8-bit code is read. This read 8-bit code is used in step S
In P9, it is determined whether or not all are 0.

If all the 8-bit codes are 0, it means that the start code is not represented.
Returning to 7, the next consecutive 8-bit code is read. If the 8-bit code is 0000 0001, the next consecutive 8-bit code is the code representing the start code. Therefore, in step SP10, the next consecutive 8-bit code is read out, and in step SP11.
After parsing as the last 8 bits of the start code with
In step SP12, it is further analyzed as a variable length code.

Further, when the read 8-bit code is neither 0000 0000 nor 0000 00001, the read 8-bit code is analyzed as the last 8 bits of the start code in step SP11. After that, in step SP12, as a variable length code,
Further analyze.

At step SP12, the currently read continuous 8-bit code is analyzed, then at step SP13, it is judged whether or not the analysis is completed, and if not completed, the processing returns to step SP1. , The next consecutive 8
Read the bit code.

Further, when 1 is set in the flag for determining whether or not the slice is formed from the intra-frame coded macro block as described above, all the macro blocks in the slice are Is intra-frame encoded, the We for macroblocks by intra-image encoding in the video sequence header shown in Table 6 is used.
Intra indicating the value of the ighting Matrix quantizer matrix
Or Picture showing the unit of picture coding in the picture layer shown in Table 7. structure, Interlaced indicating the format of the screen progressive flag, DC for DCT conversion
Intra indicating the accuracy of component quantization dc precision and Qscale indicating the type of quantization step size The flags such as type are duplicated and held in the slice header. Further, it may be arranged at a predetermined position other than the slice header.

[0144]

[Table 6]

[0145]

[Table 7]

The flag Picture The content of structure is
The flag Interlaced is shown in (a) of Table 8. progressive flag
Table 8 (b) shows the content of the flag Intra dc precisio
The content of n is shown in (c) of Table 8 with the flag Intra. dc precisi
The contents of on are shown in (d) of Table 8.

[0147]

[Table 8]

When the image data encoded by adding the respective flags is decoded, each slice is composed of macroblocks which are intra-frame encoded according to the contents of the respective flags. It is possible to determine whether or not the slice is an existing slice.

If a slice consists of intra-frame coded macroblocks,
When the slice is decoded, the picture layer, the group of picture layer, the video sequence layer, etc., which are higher layers of the slice, are decoded, and if the necessary information is already obtained, the conventional decoding is performed.

On the other hand, even when the picture layer, the group of picture layer, the video sequence layer, etc., which are higher layers of the slice, have not been decoded and necessary information has not been obtained, the slice is also recorded. By reading the information of each of the above-mentioned flags that have been added,
It is possible to decode the image data of the slice formed of the intra-frame decoded macroblock.

For example, Tables 9 and 10 show the syntax of the slice header when each of the above flags is included in the slice header.

[0152]

[Table 9]

[0153]

[Table 10]

Table 9 shows a flag structur for determining whether or not the intra-picture coded macroblock exists.
e Table 10 shows the syntax when the flag exists independently, and Table 10 shows the above flag structure. This shows the syntax when flag is indicated by the least significant bit of the slice start code.

In this case, Intra is included in the information to be transmitted.
quantizer It can be seen that the value of Weighting Matrix of the matrix flag is large. In the MPEG1 system, the Weig
Since the hting Matrix has an 8-bit precision, Weighting Matrix
A large number of bits are required to send the Matrix information. Since it is considered that the effect of this Weighting Matrix value is not so large, using the syntax omitting the value of Weighting Matrix from the syntax of the above slice header, set the value of the above Weighting Matrix appropriately and perform decoding. By doing so, the image data can be decoded, though not completely.

That is, when performing the above decoding, the We
As the value of the ighting Matrix, the value set in the slice header is used, the value set in the decoding device is used, or the Weight is set in the slice header as described above.
The value used when there is no ing Matrix value will be used.

The present invention is not limited to the above-mentioned embodiments, and it goes without saying that various other structures can be adopted.

[0158]

As is clear from the above description, in the image signal coding method according to the present invention, it is determined whether or not each slice is composed of intra-coded macroblocks. By adding the flag of
Since it is possible to apply the encoding and decoding by the I picture to the slice that is intra-image encoded, it is possible to perform unified encoding and decoding,
Further, it is possible to reduce the number of bits of the variable length code generated at the time of decoding.

Also, by adding a flag for determining whether or not the intra-picture-encoded macro block is formed by using the least significant bit of the slice start code indicating the head of the slice, the start is started. When the zero string existing before the code is detected, the start position of the start code can be specified from the content of the code detected every 8 bits, so that the processing can be performed faster than before.

Further, in the slice determined by the addition of the above flag to be composed of intra-picture-encoded macroblocks, information necessary for decoding is also added to the inside of this slice. Therefore, information belonging to a layer higher than this slice is not required, and the image data in the slice can be completely or artificially decoded by this slice alone.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of an image signal encoding device according to the present invention.

FIG. 2 is a schematic configuration diagram of an image signal decoding apparatus according to the present invention.

FIG. 3 is a flowchart showing a method according to an embodiment of the present invention.

FIG. 4 is a diagram illustrating the principle of high efficiency encoding.

[Fig. 5] Fig. 5 is a diagram for describing a type of a picture when image data is compressed.

FIG. 6 is a diagram illustrating the principle of encoding a moving image signal.

FIG. 7 is a block circuit diagram showing a configuration example of a conventional image signal encoding device and decoding device.

FIG. 8 is a diagram illustrating a format conversion operation of the format conversion circuit 17 in FIG.

9 is a block circuit diagram showing a configuration example of an encoder 18 in FIG.

10 is a diagram for explaining the operation of the prediction mode switching circuit 52 of FIG.

11 is a diagram illustrating the operation of the DCT mode switching circuit 55 in FIG.

12 is a block circuit diagram showing a configuration example of a decoder 31 of FIG.

FIG. 13 is a diagram showing a format of an image signal according to the conventional MPEG1 method.

[Fig. 14] Fig. 14 is a diagram illustrating intra-frame encoded macroblocks.

[Explanation of symbols]

111 --- Field memory group 112 --- Hybrid encoder 113 --- VLC (variable length encoder) 114, 131 ...・ ・ ・ Buffer 116 ・ ・ ・ ・ ・ ・ ・ ・ Picture counter 117 ・ ・ ・ ・ ・ ・ ・ Macro block counter 118 ・ ・ ・ ・ ・ ・ ・ Memory for storing image coding control information 119 ・ ・・ ・ ・ ・ ・ ・ ・ Slice vertical position calculation circuit 120 ・ ・ ・ ・ Output format converter 132 ・ ・ ・ ・ ・ Inverse VLC (Variable length coding) device 133 ・ ・ ・ ・・ ・ ・ ・ ・ Hybrid decoder 134 ・ ・ ・ ・ Slice vertical position restorer 136 ・ ・ ・ ・ ・ Memory for storing decoding control information 200 ・ ・ ・ ・・ Mask device 141, 201 ... Shift device

Claims (9)

[Claims] 1. An image signal encoding method including at least an intra-image encoding mode as an encoding mode selected when encoding image signal data in units of macroblocks each including a plurality of pixels, wherein the macroblock is An image signal encoding method, characterized in that a flag for determining whether or not the intra-image encoding mode is set is added to each of a plurality of slices. 2. The image signal encoding method according to claim 1, wherein the flag is added using the least significant bit of a slice start code indicating the head of the slice. 3. A picture is classified into a plurality of picture types according to a method of being coded for each picture that is one image, and the picture types include at least an intra-picture coded picture and an inter-picture predictive coded picture, In the intra-picture coded picture, the macroblock type representing the information regarding the coding for each macroblock is coded by a predetermined variable length code, and in the inter-picture predictive coded picture, the macroblock type is coded by another variable length code. 3. The image signal encoding method according to claim 1, wherein all macroblock types in the slice indicated as the intra-image encoding are encoded by the predetermined variable length code. Encoding method. 4. For each slice to which the flag is added,
The image signal encoding method according to claim 1, wherein information for decoding the slice is added. 5. An image signal encoding method using an image signal encoding method including at least an intra-image encoding mode as an encoding mode selected when encoding image signal data in units of macroblocks composed of a plurality of pixels. In the apparatus, an image signal code comprising a control unit for adding a flag for determining whether or not the intra-picture coding mode is set for each slice formed by arranging a plurality of the macro blocks Device. 6. An image signal encoding method including at least an intra-image encoding mode as an encoding mode selected when encoding image signal data in units of macroblocks composed of a plurality of pixels. An image signal decoding method characterized by performing intra-picture decoding for each slice in which a plurality of slices are arranged and in which a flag for determining whether or not to use the intra-picture coding mode is detected. 7. The zero is added when the flag is added by using the least significant bit of a slice start code indicating the head of the slice and a series of zeros existing consecutively before the slice start code is detected. 7. The image signal decoding method according to claim 6, wherein the head of the slice start code is detected by detecting every 8 bits. 8. For each slice to which the flag is added,
The image signal encoding method according to claim 7, wherein decoding is performed using information for decoding the slice. 9. An image signal decoding method using an image signal encoding method including at least an intra-image encoding mode as an encoding mode selected when encoding image signal data in units of macroblocks composed of a plurality of pixels. The apparatus is characterized in that intra-picture decoding is performed for each slice formed by arranging a plurality of the macroblocks, in units of slices in which a flag for determining whether to use the intra-picture coding mode is detected. Image signal decoding device.