JP3500340B2 - Coding apparatus and method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to recording a moving image signal on a recording medium such as a magneto-optical disk or a magnetic tape and reproducing the same to display it on a display or the like, a video conference system or a video telephone system. The present invention relates to a decoding device and method suitable for use in a case where a moving image signal is transmitted from a transmitting side to a receiving side through a transmission path such as a broadcasting device, and the receiving side receives and displays the moving image signal. is there.

[0002]

2. Description of the Related Art In a system for transmitting a moving image signal to a remote place such as a video conference system or a video telephone system, in order to efficiently use a transmission path, line correlation or inter-frame correlation of video signals is required. Is used to compress and code an image signal.

When the line correlation is used, the image signal can be compressed by, for example, DCT (discrete cosine transform) processing.

Further, by utilizing the inter-frame correlation, the image signal can be further compressed and encoded. For example, as shown in A of FIG. 6, time t = t1, t2, t3
In FIG. 6, when the frame images PC1, PC2, and PC3 are generated, the difference between the image signals of the frame images PC1 and PC2 is calculated, and the image P as shown in B of FIG.
C12 is generated, and the frame image PC2 of FIG.
And PC3 are calculated to generate the image PC23 of B in FIG. Normally, the images of frames that are temporally adjacent do not have such a large change, so when the difference between the two is calculated, the difference signal has a small value. That is, in the image PC 12 shown in FIG. 6B, A in FIG.
As the difference between the image signals of the frame images PC1 and PC2 of
A signal in the shaded area in the image PC12 of FIG. 6B is obtained, and in the image PC23 shown in B of FIG. 6, the difference between the image signals of the frame images PC2 and PC3 of A of FIG. The signal of the shaded portion in the image PC23 of FIG. 6B is obtained. Therefore, if this difference signal is encoded, the code amount can be compressed.

However, if only the difference signal is transmitted, the original image cannot be restored. Therefore, the image of each frame is an I picture (Intra-coded picture), P picture (Forward predictive coded picture: Perdictive-coded picture) or B picture (Quantity direction predictive coded picture: Bidirectionally-codedp).
image), and the image signal is compressed and encoded.

That is, for example, as shown in FIGS. 7A and 7B, image signals of 17 frames from frames F1 to F17 are set as a group of pictures, which is 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, the image signal of the P picture is basically as shown in FIG.
As indicated by A, the difference from the image signal of the I picture or P picture preceding in time is encoded and transmitted. Further, as the image signal of the B picture, basically, as shown in B of FIG. 7, a difference from the average value of both the temporally preceding frame and the subsequent frame is obtained, and the difference is encoded. To transmit.

FIGS. 8A and 8B show the principle of the method of encoding a moving image signal in this way. It is to be noted that FIG. 8A schematically shows frame data of a moving image signal, and FIG. 8B schematically shows transmitted frame data. As shown in FIG. 8, since the first frame F1 is processed as an I picture, that is, a non-interpolation frame,
The data is directly transmitted as transmission data F1X (transmission non-interpolation frame data) to the transmission path (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.
The difference from the average value of (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 coding), and the same processing as in the I picture is performed. In the second process, the difference from the frame F3 that is temporally later is calculated, and the broken line arrow SP2 in the figure is calculated.
The difference is transmitted as shown by (backward predictive coding). The third process is to transmit the difference with respect to the temporally preceding frame F1 as indicated by the dashed arrow SP3 in the figure (forward predictive coding). Furthermore, the fourth processing is
As shown by the broken line arrow SP4 in the figure, the difference between the temporally preceding frame F1 and the subsequent frame F3 average value is generated and transmitted as transmission data F2X (bidirectional predictive coding).

Of these four methods, the method with the least amount of transmission 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 (prediction image) (frame F1 in the case of forward prediction)
Between F and F2), or motion vector x
2 (motion vector between frames F3 and F2 for backward prediction) or both motion vectors x1 and x2 (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
Data is transmitted as it is as transmission data F3X (indicated by a dashed arrow SP1) (intra-encoding). This P
Which method is used to transmit a picture is the same as in the case of a B picture, and 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 to obtain transmission data F4X, F5X, motion vectors x4, x5, x6 and the like.

FIG. 9 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 this. 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 converters 12 and 1 are respectively separated.
A / D conversion is performed at 3. The video signal converted into a digital signal by A / D conversion by the A / D converters 12 and 13 is
It is supplied 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 1.
6 are stored respectively.

The format conversion circuit 17 converts the frame format signal stored in the frame memory 14 into
Convert to block format signal. That is, FIG.
(A), the video signal stored in the frame memory 14 is frame format data in which V lines of H dots per line 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. 10, each macroblock is composed of luminance signals corresponding to 16 × 16 pixels (dots), and this luminance signal is, as shown in (C) of FIG. 8 more
Blocks Y [1] to Y [4] in units of × 8 dots
It is divided into. Then, the 16 × 16 dot luminance signal includes an 8 × 8 dot Cb signal and an 8 × 8 dot Cb signal.
The r signal is matched.

The data thus converted into the block format 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.
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. Then, the luminance signal of the frame format is supplied to and stored in the luminance signal frame memory 34 of the frame memory 33, and the color difference signal is supplied 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.
A-converted, supplied to the post-processing circuit 38, and combined.
This output video signal is output from the output terminal 30 to a display such as a CRT (not shown) and displayed.

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

The image data to be encoded supplied through the input terminal 49 is input to the motion vector detection circuit 50 in macroblock units. The motion vector detection circuit 50 processes the image data of each frame as an I picture, a P picture, or a B picture according to a preset predetermined sequence. Which of I, P, and B pictures to sequentially process the images of the respective frames to be processed is predetermined (for example, as shown in FIG. 7, the frames F1 to F1 are processed).
The group of pictures composed of 7 is I, B,
Processed as P, B, P, ... B, P).

Image data of a frame (for example, frame F1) processed as an I picture is transmitted from the motion vector detecting circuit 50 to the front original image portion 51a of the frame memory 51.
The image data of the frame (for example, the frame F2) that is transferred and stored in the B picture is transferred to and stored in the original image section (reference original image section) 51b and is processed as the P picture (for example, the frame F3). The image data of) is transferred and stored in the rear original image portion 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 (the frame F5) is input, an image of the first P picture (frame F3) stored in the backward original image portion 51c until then. The data is transferred to the forward original image portion 51a, the image data of the next B picture (frame F4) is stored (overwritten) in the original image portion 51b, and the next P picture (frame F5) is stored.
Image data is stored (overwritten) in the rear original image portion 51c.
To be done. 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 the frame prediction mode process or the field prediction mode process. Furthermore, under the control of the prediction determination circuit 54, the calculation unit 53 performs calculation of intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction. Which of these processes is to be performed is determined in accordance with the prediction error signal (difference between the reference image to be processed and the predicted image corresponding thereto). 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. 12A, the data of the odd field lines and the data of the even field lines are mixed in each luminance block. Note that the solid lines in each macroblock of FIG. 12 indicate the data of the lines of the odd field (the line of the first field), and the broken lines indicate the data of the lines of the even field (the line of the second field). Symbols a and b indicate units of motion compensation. In this 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 indicates that when the field prediction mode is set, FIG.
The signal input from the motion vector detection circuit 50 in the configuration shown in A of FIG. 12 is converted into the luminance blocks Y [1] and Y [2] of the four luminance blocks as shown in B of FIG. The two luminance blocks Y [3] and Y [4] are composed only of the dots of the field lines, and the other two luminance blocks Y [3] and Y [4] are composed of the data of the even field lines and output to the arithmetic unit 53. In this case, one motion vector is associated with the two luminance blocks Y [1] and Y [2], and the other two luminance blocks Y [3] and Y [3].
Another motion vector is associated with [4].

Describing in accordance with the configuration of FIG. 11, 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 A of FIG. It Further, in the field prediction mode, as shown in B of FIG. 12, the upper half (4 lines) of each color difference block Cb, Cr is the color difference of the odd field corresponding to the luminance blocks Y [1], Y [2]. Signal, and the lower half (4 lines) is the luminance block Y
Color difference signals of even fields corresponding to [3] and Y [4] are set.

Further, the motion vector detection circuit 50 uses the prediction determination circuit 54 in the image prediction,
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 calculated 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 judgment 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
Is a configuration 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 as shown in FIG. 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 absolute values of the corresponding prediction errors is selected.

The prediction determination circuit 54, when the motion vector detection circuit 50 is reading the image data of the I picture from the forward original image portion 51a, uses the intra-frame (image) prediction mode (the mode without motion compensation) 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.

This DCT mode switching circuit 55, as shown in FIG. 13A or 13B, stores data of four luminance blocks in a state where lines of odd fields and lines of even fields are mixed (frame DCT mode), Alternatively, it is output to the DCT circuit 56 in either of the separated states (field DCT mode).

That is, the DCT mode switching circuit 55 is
Mixed data of odd field and even field D
Comparing the coding efficiency in the case of CT processing and the coding efficiency in the case of DCT processing in the separated state,
Select a mode with good coding efficiency.

For example, as shown in FIG. 13A, the input signal has a structure in which odd field lines and even field lines are mixed and the signal of the odd field line and the signal of the even field line that are vertically adjacent to each other. Then, the sum (or sum of squares) of the absolute values is calculated. Further, as shown in FIG. 13B, the input signal has a configuration 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 field vertically adjacent to each other and the line of the even field are The difference between the signals of is calculated, and the sum (or sum of squares) of the absolute values of each is calculated. Further, both (sum of absolute values) are compared, and the DCT mode corresponding to a smaller value is set. That is, if the former is smaller, the frame DCT mode is set, and if the latter is smaller, the field DCT mode is set.

Then, the data having the structure 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. 12) and the DCT mode in the DCT mode switching circuit 55 (see FIG. 13), 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 DCT mode switching circuit 55 is also in the frame DCT mode (odd lines and even lines are mixed). 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. This 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, and then,
It is 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, a quantization step (scale) is set by the quantization circuit 57, and a prediction mode (intra-picture prediction, forward prediction, backward prediction, or bidirectional prediction is set by the prediction determination circuit 54. Mode indicating whether or not the motion vector is detected by 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 stores the input data, and quantizes the data corresponding to the stored amount in the quantizing circuit 57.
Output to.

The transmission buffer 59 increases the quantization scale of the quantization circuit 57 by the quantization control signal when the remaining amount of data increases to the allowable upper limit value.
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 read out at a predetermined timing and output to the output terminal 69.
It is output to the transmission path via 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 corresponding to 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 converts the image data of each frame sequentially input into
For example, as described above, I, B, P, B, P, B ...
When each is processed as a picture, the image data of the first input frame is processed as an I picture, and then the image of the next input frame is further processed as a B picture. The image data of the frame is processed as a P picture. This is because a B picture is accompanied by backward prediction and cannot be decoded unless a 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
When d is switched to the contact point b, the image data (in this case, an I-picture image) stored in the forward prediction image portion 63a of the frame memory 63 is read out, and the motion compensation circuit 64 causes the motion vector detection circuit 50 to read. Is motion-compensated corresponding to the motion vector output by. 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 the 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 calculator 62 is also supplied with the same data as the predicted image data supplied to the calculator 53a. 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 the P picture is supplied to and stored in the backward predicted image portion 63b of the frame memory 63.

In this way, the motion vector detecting circuit 50 executes the processing of the B picture after the data of the I picture and the P picture are stored in the forward prediction image section 63a and the backward prediction image section 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 data (in this case, the P picture image) data stored in the backward prediction image section 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.
2 and processed in units of macroblocks shown in FIG. 13 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. 14 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 via the input terminal 80, 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, and obtains the motion vector, the prediction mode, the prediction flag and the DCT flag from the motion compensation circuit 8.
7, the quantization step is output to the inverse quantization circuit 83, and the decoded image data is output to the inverse quantization circuit 83.

The inverse quantizing circuit 83 is a 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 is input later to the arithmetic unit 85 (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. 9).

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, as in the case of 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 input after the B picture is input). Pictures have been processed and transmitted before 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 which has been motion-compensated by the motion compensation circuit 87 in this way is sent to the IDC in the calculator 85.
It is added to the output of the T circuit 84. This addition output is output to the format conversion circuit 32 via the output terminal 91.

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-predicted image portion 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 DC in the encoder 18 of FIG.
Although the circuits corresponding to the T mode switching circuit 55 are not shown, the processing corresponding to these circuits, that is, the configuration in which the signals of the lines of the odd field and the even field are separated is necessary for the original mixed configuration. The process of returning according to
The motion compensation circuit 87 executes this.

Further, although the processing of the luminance signal has been described above, the processing of the color difference signal is similarly performed.
However, in this case, the motion vector used is one for the luminance signal, which is halved in the vertical and horizontal directions.

Here, the quality of the image transmitted in the above-mentioned image signal encoding / decoding is controlled as shown in FIG. For example, the SNR (SN ratio) of an image is
Control is performed according to the so-called picture type, which represents the type of coding such as intra-picture coding, forward predictive coding, and bidirectional predictive coding described above. Transmitted with inferior quality. That is, if all images can be transmitted at a high transmission rate, more preferable image quality can be obtained, but there are cases where it is not possible to select a transmission rate higher than a certain value due to the characteristics of the transmission path. As the visual characteristic, the transmission method as shown in FIG. 15 is adopted by utilizing the characteristic that the image impression is improved by vibrating the image quality as shown in FIG. 15 rather than averaging all the image quality. As a result, a higher quality image is obtained at a certain transmission rate. Therefore, in the configuration of FIG. 12, the quantizer 57 controls the transmission rate so as to achieve this image quality.

[0080]

By the way, FIG. 16 shows a case where the above-mentioned image signal encoding device / decoding device is connected in tandem in series.

In FIG. 16, an analog video signal is supplied as an input signal a to the input terminal 200,
It is sent to the image signal encoding device 201. In this image signal coding apparatus 201, the analog video signal input signal a is converted into a digital video signal by the A / D converter 211, and this signal is coded by the coding circuit 212 as described above. The output (encoded digital video signal) of the encoding circuit 212 is the image signal decoding device 2 of the next stage.
Sent to 02. A

In the image signal decoding device 202, the supplied encoded digital video signal is decoded by the decoding circuit 213, converted into an analog signal by the D / A converter 214, and output. The output signal b, which is the analog video signal, is sent to the image signal encoding device 203 similar to the image signal encoding device 201 in the next stage.

Similarly, this image signal coding device 20
The coded digital video signal from 3 is an image signal decoding device 20 similar to the above image signal decoding device 202.
4 and the output signal c, which is an analog video signal from the image signal decoding device 204, is output via the terminal 205 or is further sent to an image signal encoding device or the like connected thereto.

Here, an analog video signal from the encoding / decoding device in the first stage having the tandem connection configuration, that is, an output signal b from the image signal decoding device 202, and 2
FIG. 17 shows changes in the SNR (SN ratio) of the image in the analog video signal from the encoding / decoding device of the second stage, that is, the output signal c from the image signal decoding device 204.

In FIG. 17, it can be seen that the output signal c has a significantly lower SNR than the output signal b. This is because the picture type applied in the first stage encoding / decoding device and the picture type applied in the second stage encoding / decoding device are different. That is, in the first stage encoding / decoding device, B
The image coded as a picture is coded in the second stage /
When the decoding apparatus encodes the picture as a P picture, for example, since the picture quality is vibrated in accordance with the picture type as described above, the picture quality is greatly deteriorated.

Further, since the picture quality deterioration due to this tandem connection is due to the difference in picture type between stages, this is caused by digital connection between codecs (between encoding / decoding devices). It also occurs when

FIG. 18 shows a connection state in the case of this digital connection.

In FIG. 18, the analog video signal input through the terminal 300 is converted into digital data by the A / D converter 301 and supplied to the image signal encoding device 302. This image signal encoding device 302
Then, the digital video data is sent to the encoding circuit 312 via the digital interface 311, and is encoded (compressed) by the encoding circuit 312 to be converted into a digital video bit stream.

The digital video signal (bit stream of the compressed signal) from the encoding circuit 312 is sent to the image signal decoding device 303, and this image signal decoding device 3
It is decoded by the decoding circuit 313 in 03 and is output as a digital video signal (output signal b) via the digital interface 314.

This digital video signal is an image signal coding device 304 similar to the above image signal coding device 302.
Sent to. Similarly, the image signal encoding device 30 will be described below.
The encoded digital video signal (compressed signal bit stream) from 4 is further decoded by an image signal decoding device 305 similar to the above-described image signal decoding device 303, and from this image signal decoding device 305. The digital video signal of is converted into an analog video signal (output signal c) by the D / A converter 306, and then output from the terminal 307.

Also in the digital connection shown in FIG. 18,
The same problem as described above with reference to FIG. 17 occurs.

Therefore, the present invention has been made in view of such a situation, and in the case of tandem connection,
An object of the present invention is to provide a coding apparatus and method that realize an encoding process and a decoding process with little deterioration in image quality.

[0093]

[0094]

[0095]

[0096]

[0097]

[0098]

A coding device according to the present invention is a coding device for performing coding processing and decoding processing on an encoded stream, and selects the encoded stream from the encoded streams. Video data obtained by extracting picture type information indicating a picture type in the applied past encoding processing, decoding the encoded stream based on the extracted picture type information, and decoding by the decoding means. And a decoding means for transmitting the picture type information, and a code for the video data having the same picture type as the picture type indicated by the picture type information transmitted from the decoding means and decoded by the decoding means. The video data is encoded by performing the encoding process, and the obtained encoding stream is obtained. By having a coding means for outputting the over arm and the picture type information, to solve the problems described above.

The coding method of the present invention is a coding method for performing coding processing and decoding processing on a coded stream, and the coding method applied to the coded stream from the coded stream. The picture type information indicating the picture type in the encoding process is extracted, the coded stream is decoded based on the extracted picture type information, and the video data and the picture type decoded by the decoding means are extracted. And a decoding step for transmitting information, and an encoding process for the video data decoded by the decoding means with the same picture type as the picture type indicated by the picture type information transmitted from the decoding means. By encoding the above video data, and the obtained encoded stream By having a coding step of outputting and the picture type information, to solve the problems described above.

[0100]

[0101]

That is, according to the present invention, in the multi-stage tandem connection, the first-stage decoding means extracts the picture type information indicating the picture type in the past encoding process applied to the encoded stream, and extracts this picture. The coded stream is decoded based on the type information, and the decoded video data and the picture type information are transmitted to the encoding device, and the encoding means displays the picture indicated by the picture type information transmitted from the decoding means. By encoding the decoded video data with the same picture type as the type and outputting the obtained encoded stream and picture type information to the decoding means in the next stage, the picture type in the first stage encoding and the next It is possible to match the picture type in the stage encoding.

[0103]

BEST MODE FOR CARRYING OUT THE INVENTION Preferred embodiments of the present invention will be described with reference to the drawings.

First, the case of analog connection will be described as the first embodiment.

The image signal transmission device (image signal encoding device / decoding device) of the first embodiment to which the coding device and method of the present invention are applied is connected in tandem in series (in this embodiment, two stages are provided). The case of connection) is shown in FIG.

The image signal transmitting apparatus according to the present embodiment encodes / decodes an image according to a picture type of any one of I picture, P picture and B picture, and transmits the image. The image signal decoding device 121, the encoding device 122, and the decoding device 123 are connected in serial tandem, and the image signal encoding devices 120 and 12 are connected.
In the image signal decoding devices 121 and 123 for decoding the image signal encoded by 2 (in this case, the encoding devices 120 and 122 perform A / D conversion to form a digital video signal bit stream), The picture types at the time of coding in the image signal coding apparatuses 120 and 122 are detected by the decoding circuits 103 and 110, and the picture types are applied to the analog video signals after D / A conversion in the D / A converters 104 and 109. Of the analog ID signal representing the picture type is multiplexed by the multiplexing circuits 105 and 111, and in the image signal coding device 122, the ID signal representing the picture type multiplexed into the analog video signal (output signal b) by the separation circuit 106 is generated. Then, the encoding circuit 108 separates the analog video signal into an intra-picture code according to the separated picture type. , In which so as to encode the forward predictive coding, the bidirectional predictive coding. Note that the encoding circuit 102 of the image signal encoding device 120 in the first stage encodes the A / D conversion output of the analog video signal (input signal a) based on the picture type (ID signal) from the terminal 118. It has become.

That is, in FIG. 1, the input terminal 10
An analog video signal is supplied to 0 as an input signal a and is sent to the image signal encoding device 120. In this image signal coding device 120, the analog video signal input signal a is converted into a digital video signal by the A / D converter 101, and this signal is coded by the coding circuit 102.
At the time of encoding by the encoding circuit 102, the terminal 118
Either intra-picture coding, forward predictive coding, or bidirectional predictive coding is performed based on the ID signal representing the picture type supplied via the. The output of the encoding circuit 102 becomes the output signal of the image signal encoding device 120, and the bit stream of the encoded digital video signal is sent to the image signal decoding device 121 of the next stage. The encoding circuit 120 can also be configured to be capable of encoding without supplying the picture type.
The encoding circuit 120 in this case can be realized by using the same configuration as that of FIG. 11 described above.

In the image signal decoding device 121, the supplied encoded digital video signal is decoded by the decoding circuit 103, and at the same time, the decoding circuit 103 detects the ID signal representing the picture type. In the multiplexing circuit 105 of the image signal decoding device 121, the analog video signal obtained by converting the digital video signal decoded by the decoding circuit 103 by the D / A converter 104 and the picture type ID are displayed. And signals. The multiplexing circuit 105 multiplexes and outputs the ID signal during the vertical blanking period of the analog video signal. The output of the multiplexing circuit 105 is output as an analog video signal (output signal b) from the image signal decoding device 121.

The output signal b from the image signal decoding device 121 is sent to the image signal encoding device 122 at the next stage. The output signal b supplied to the image signal encoding device 122 is supplied to the separation circuit 106. The separation circuit 106 separates the analog video signal from the ID signal, and the analog video signal is A / D converter 1
At 07, the ID signal is sent to the encoding circuit 108. In the encoding circuit 108, the A / D converter 10 is used.
The video signal converted into a digital signal in 7
Encoding is performed based on the picture type corresponding to the D signal.
The output of the encoding circuit 108 becomes the output (bit stream of digital video signal) of the image signal encoding device 122.

The bit stream from the image signal coding device 122 is further used in the image signal decoding device 12 at the next stage.
3 is supplied. In the image signal decoding device 123,
The supplied encoded digital video signal is decoded by the decoding circuit 110 and the ID signal representing the picture type is detected. The image signal decoding device 12
The digital video signal decoded by the decoding circuit 110 is sent to the D / A converter 109 in the multiplexing circuit 111 of No. 3 of FIG.
The analog video signal converted by and the picture type ID signal are supplied. The multiplexing circuit 111 multiplexes and outputs the ID signal during the vertical blanking period of the analog video signal. The output of the multiplexing circuit 111 is the image signal decoding device 12
3 is output as an analog video signal (output signal c), and is further sent to the subsequent stage configuration via the terminal 119.

That is, in the tandem connection of FIG. 1, the picture type (ID signal) is the codec of the first stage (image signal encoding device 120 and decoding device 12).
1 is coded (encoded / decoded) and the codec of the second stage codec (encoded / decoded by the image signal encoding device 122 and the decoding device 123) is transmitted to match. It has become so.

The SNRs of the first stage video output signal b and the second stage video output signal c in the above-described configuration of FIG.
(SN ratio) is shown in FIG. From FIG. 2, by matching the picture types of the first-stage codec and the second-stage codec as described above, the picture types of the first-stage codec and the second-level codec do not differ from each other. Even if you vibrate the image quality according to the type,
It is possible to minimize the deterioration of the image due to the tandem connection.

Next, as a second embodiment of the present invention,
The case of digital connection is described below.

FIG. 3 shows a connection state when the image signal encoding device / decoding device as the image signal transmitting device of the second embodiment is digitally connected in tandem.

That is, in FIG. 3, the input terminal 14
An analog video signal is supplied to 0 as an input signal a, and the analog video signal is converted into a digital video signal by an A / D converter 141. This digital video signal is sent to the image signal encoding device 142. In this image signal coding device 142, the digital video signal is sent to the coding circuit 152 via the digital interface 151. The encoding circuit 152 includes a terminal 14
An ID signal representing the picture type is also supplied via 8.
The digital video signal based on the ID signal,
The coding is performed by any one of intra-picture coding, forward predictive coding, and bidirectional predictive coding. The output of the encoding circuit 152 becomes the output signal (bit stream of the compressed signal) of the image signal encoding device 142, and the bit stream of the compressed signal is sent to the image signal decoding device 143 at the next stage. It should be noted that even with the configuration of FIG. 3, the image signal encoding device 142 can be configured to perform encoding without using the picture type, as in the first embodiment described above.

In the image signal decoding device 143, the decoding circuit 1 decodes the supplied digital video signal of the compressed signal.
I, which is decoded at 53 and represents the above picture type
D signal is detected. To the multiplexing circuit 155 of the image signal decoding apparatus 143, the digital video signal decoded by the decoding circuit 153 and passed through the digital interface 154 and the picture type ID signal are supplied. The multiplexing circuit 155 multiplexes the ID signal in the format of the digital video signal as a flag for each image unit. The multiplexing circuit 15
The output 5 is output as a digital video signal (output signal b) from the image signal decoding apparatus 143.

The output signal b from the image signal decoding device 143 is sent to the image signal encoding device 144 in the next stage. The output signal b supplied to the image signal encoding device 144 is supplied to the separation circuit 156. The separation circuit 156 separates the digital video signal and the ID signal, and sends the digital video signal to the digital interface 157 and the ID signal to the encoding circuit 158. The encoding circuit 158 encodes the digital video signal through the digital interface 157 based on the picture type corresponding to the ID signal. The output of the encoding circuit 158 becomes the output (bit stream of the compressed signal) of the image signal encoding device 144.

The bit stream from the image signal encoding device 144 is further used in the image signal decoding device 14 at the next stage.
5 is supplied. In the image signal decoding device 145,
Decoding circuit 1 for the bit stream of the supplied compressed signal
I, which is decoded at 60 and represents the above picture type
D signal is detected. The digital video signal decoded by the decoding circuit 160 and passed through the digital interface 159 and the picture type ID signal are supplied to the multiplexing circuit 161 of the image signal decoding device 145. The multiplexing circuit 161 multiplexes and outputs the ID signal as a flag in the format of the digital video signal. The output of the multiplexing circuit 161 is further converted into an analog video signal (output signal c) by the D / A converter 146, and this is sent to the subsequent stage configuration via the terminal 147.

Also in the digital connection of FIG. 3, the picture type (ID signal) is the same as the picture type of the first stage codec (encoding / decoding in the image signal encoding device 142 and the decoding device 143). Stage codec (image signal encoding device 144 and decoding device 145
It is designed to be transmitted in order to match with the picture type of (encoding / decoding in 1).

SNRs of the first stage video output signal b and the second stage video output signal c in the above-described configuration of FIG.
As shown in FIG. 2 described above, the (SN ratio) also eliminates the discrepancy between the picture types in the first stage and the second stage. Therefore, even if the image quality is vibrated corresponding to the picture type as described above, It is possible to minimize the deterioration of the image due to the tandem connection.

Finally, FIG. 4 shows a more specific configuration of the encoding circuit in each image signal encoding device in the above-described first and second embodiments. In addition, in FIG.
The same components as those in FIG. 11 described above are designated by the same reference numerals, and detailed description thereof will be omitted.

In FIG. 4, an ID signal representing the picture type is supplied from the terminal 70, and this ID signal is
It is sent to the motion vector detection circuit 50, the prediction determination circuit 54, and the variable length coding circuit 58, and the processing according to the picture type is performed on these constituent elements.

Further, FIG. 5 shows a more specific structure of the decoding circuit in each image signal decoding apparatus in the above-described first and second embodiments. Also in FIG. 5, the same components as those in FIG. 14 described above are designated by the same reference numerals, and detailed description thereof is omitted.

In FIG. 5, the variable length decoding circuit 82
Detects the above-mentioned picture type in addition to the above-described prediction mode, motion vector, frame / field prediction flag, and frame / field DCT flag, and sends a signal representing this picture type to the motion compensation circuit 87. The motion compensation circuit 87 performs motion compensation according to this picture type. Further, the ID signal indicating the detected picture type is output to the subsequent stage from the terminal 92.

As described above, according to the present embodiment, in the multi-stage tandem connection, the signal indicating the picture type is output together with the output image signal of the first stage, and the input corresponding to the picture type is input at the next stage. By making it possible, the picture type in the first-stage decoding and the picture type in the next-stage encoding can be matched. This makes it possible to minimize the deterioration of image quality in the tandem connection of the codec. Also,
Even in the case of digital connection, by transmitting the picture type and the image data between the stages without changing the digital data, the picture type in the decoding in the first stage and the picture type in the encoding in the next stage can be matched. Similarly, it is possible to minimize the image quality deterioration. As described above, the present embodiment is an effective method for multistage tandem connection in which the number of restorations is two or more.

[0126]

[0127]

[0128]

As described above, according to the present invention,
The first-stage decoding means extracts picture type information indicating a picture type in the past coding processing performed on the coded stream, decodes the coded stream based on the picture type information, and decodes the coded stream. The encoded video data and the picture type information are transmitted to the encoding means, and the encoding means encodes the decoded video data with the same picture type as the picture type indicated by the picture type information transmitted from the decoding means. Then, the obtained encoded stream and the picture type information are output to the decoding means in the next stage, whereby the encoding processing and the decoding processing with less deterioration of the image quality can be realized in the case of tandem connection.

[0129]

[Brief description of drawings]

FIG. 1 is a block circuit diagram showing a tandem connection (in the case of analog connection) of a video codec according to a first embodiment of the present invention.

FIG. 2 is a diagram for explaining a decrease in SNR in tandem connection in consideration of a picture type according to the embodiment of the present invention.

FIG. 3 is a block circuit diagram showing a tandem connection (for digital) of a video codec according to a second embodiment of the present invention.

FIG. 4 is a block circuit diagram showing a specific configuration of an encoding circuit in the image signal encoding device according to the embodiment of the present invention.

FIG. 5 is a block circuit diagram showing a specific configuration of a decoding circuit in the image signal decoding device according to the embodiment of the present invention.

FIG. 6 is a diagram illustrating the principle of high efficiency encoding.

[Fig. 7] Fig. 7 is a diagram for describing picture types in the case of compressing image data.

FIG. 8 is a diagram illustrating the principle of encoding a moving image signal.

FIG. 9 is a block diagram showing a configuration example of a conventional image signal encoding device and decoding device.

FIG. 10 is a diagram illustrating a format conversion operation of the format conversion circuit 17 in FIG.

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

12 is a diagram illustrating the operation of the prediction mode switching circuit 52 in FIG.

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

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

FIG. 15 is a diagram illustrating rate control according to a picture type.

FIG. 16 is a block circuit diagram showing a tandem connection (in the case of analog connection) of a conventional video codec.

FIG. 17 is a diagram for explaining a decrease in SNR in a tandem connection that does not consider a conventional picture type.

FIG. 18 is a block circuit diagram showing a tandem connection (in the case of digital connection) of a conventional video codec.

[Explanation of symbols]

1 encoding device, 2 decoding device, 3 recording medium,
12, 13 A / D converter, 14 frame memory, 15 luminance signal frame memory, 16 color difference signal frame memory, 17 format conversion circuit, 1
8 encoders, 31 decoders, 32 format conversion circuits, 33 frame memories, 34 luminance signal frame memories, 35 color difference signal frame memories, 36, 37 D / A converters, 50 motion vector detection circuits, 51 frame memories, 52 prediction mode switching Circuit, 53 arithmetic unit, 54 prediction determination circuit, 55 DCT mode switching circuit, 56 D
CT circuit, 57 quantization circuit, 58 variable length coding circuit, 59 transmission buffer, 60 inverse quantization circuit,
61 IDCT circuit, 62 arithmetic unit, 63 frame memory, 64 motion compensation circuit, 81 reception buffer, 82 variable length decoding circuit, 83 inverse quantization circuit, 84 IDCT circuit, 85 arithmetic unit, 86
Frame memory, 87 Motion compensation circuit, 101,1
07,141 A / D converter, 102,108,15
2, 158 encoding circuit, 103, 110, 153
160 decoding circuit, 104, 109, 146 D / A
Converter, 105, 111, 155, 161 multiplex circuit, 106, 156 separation circuit, 120, 122,
142,144 image signal encoding device, 121,12
3, 143, 145 Image signal decoding device, 151,
154, 157, 159 Digital interface

Claims (2)

(57) [Claims] 1. A coding apparatus for performing an encoding process and a decoding process on an encoded stream, wherein a picture type in a past encoding process performed on the encoded stream is selected from among the encoded streams. Decoding means for extracting the indicated picture type information, decoding the encoded stream based on the extracted picture type information, and transmitting the video data decoded by the decoding means and the picture type information. And the picture type information transmitted from the decoding means
The video data is coded by performing a coding process on the video data decoded by the decoding means with the same picture type as that shown in, and the obtained coded stream and the picture type information are A coding device comprising: a coding means for outputting. 2. A coding method for performing an encoding process and a decoding process on an encoded stream, wherein a picture type in a past encoding process performed on the encoded stream is selected from among the encoded streams. A decoding step of extracting the picture type information shown, decoding the encoded stream based on the extracted picture type information, and transmitting the video data decoded by the decoding means and the picture type information. And the picture type information transmitted from the decoding means
The video data is coded by performing a coding process on the video data decoded by the decoding means with the same picture type as that shown in, and the obtained coded stream and the picture type information are And a coding step for outputting.