JP2003143608A - Apparatus and method for encoding moving picture, and code sequence transmission method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve problems in a conventional method for editing a code sequence that it has difficulty in editing the code sequence for a conventional GOP configuration, deteriorates a coding efficiency for a closed GOP configuration and causes discontinuity in periods of P pictures. SOLUTION: A circuit section from a subtractor 3 to an inverse DCT 11 encodes part of a received image into a P picture and obtains a first local decoded image through local decoding. A circuit section from a switch 19 to an inverse DCT 16 encodes part of the picture encoded by the P picture as a particular picture and encodes it into an I picture and obtains a second local decoded image through local decoding. After an adder 26 sums the locally decoded images, an inter-image prediction unit 27 uses the sum for a reference image for inter-image prediction of the other pictures. A multiplexer 13 outputs a code sequence comprising GOPs each comprising a code sequence started from the I picture of the particular picture and ended in a B picture just before the particular picture.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a moving picture coding apparatus,
The present invention relates to a moving image coding method and a code string transmission method, and in particular, in order to efficiently transmit, store, and display an image, high-efficiency coding that converts image information into a digital signal with a smaller code amount, in-picture independence, In moving picture coding using three kinds of coding methods of unidirectional prediction and bidirectional prediction, a moving picture coding apparatus, a moving picture coding method, and a moving picture coding method that facilitate editing of a code string while suppressing a decrease in coding efficiency. The present invention relates to a code string transmission method.

[0002]

2. Description of the Related Art The MPEG (Moving Picture Experts Group) system has been known as a high-efficiency compression coding system for moving images. This MPEG system has three types of pictures depending on the inter-picture prediction method. An intra-picture independent coded picture called an I picture, a unidirectional predictive coded (interframe or interfield forward predictive coded) picture called a P picture, and a bidirectional predictive coded picture called a B picture. The I picture supports random access and channel switching, and decoding can be performed from there. Here, a picture refers to one frame or one field of a moving image.

A plurality of pictures are bundled in a code string to form a code string group, that is, a GOP (Group Of Picture).
In this GOP, one I picture is always included. A normal GOP structure starts with a B picture and ends with a P picture. This picture structure is shown in FIG.
Shown in. Since the order of the P (I) picture and the B picture is exchanged in the code string, this structure is obtained.

On the other hand, the first B picture is the P of the previous GOP.
Since prediction is also made from pictures, inter-picture prediction is not interrupted, and code strings cannot be replaced in GOP units. Therefore, there is a method of eliminating the first B picture and making the I picture immediately after the P picture of the previous GOP. This is called a closed GOP, and since each GOP has nothing to do with the preceding and following GOPs, the code string can be edited in GOP units. This GOP structure is shown in FIG. In this case, since the first part is not a periodic process, the process is a little complicated. Further, since the B picture having a small code amount is deleted, the average code amount increases.

On the other hand, the present inventor first disclosed in Japanese Patent Laid-Open No. 11-164.
As disclosed in Japanese Patent Laid-Open No. 307, there are a moving picture coding apparatus and a moving picture decoding apparatus that multiplex a code string that is independently coded in a picture as a sub code string in addition to the main code string. In this moving picture coding apparatus, main coding is performed on an input moving picture by performing intra-picture independent coding or inter-picture predictive coding by switching in frame or field units and outputting the obtained main code string. Means, and sub-encoding means for performing intra-image independent encoding of a predetermined frame or field of frames or fields for which inter-picture predictive encoding is performed in the main encoding means, and outputting the obtained sub-code sequence, It is characterized by comprising a code string multiplexing means for inserting a sub code string of the predetermined frame or field into a portion adjacent to the main code string of the predetermined frame or field to obtain a multiplexed code string.

Further, the above moving picture decoding apparatus detects the type (main code sequence / sub code sequence) of the input code sequence from the header of the code sequence and outputs the type information of the code sequence. Then, based on the type information of the code string, when the continuous images are not decoded, any input code string is guided to the decoding process, and the continuous images are decoded. In this case, the intra-image decoding or the inter-image predictive decoding is performed on the code string control means for discarding the sub code string and guiding only the main code string to the decoding process, and the code string given from the code string control means. And a decoding unit for outputting the obtained reproduced image.

[0007]

FIG. 1 is a block diagram of a moving picture coding apparatus and a moving picture decoding apparatus proposed by the inventor of the present invention.
Only at the time of random access or channel switching, it is possible to decode from a code string that is independently coded in a picture.

There is also a method of improving the image quality by using both a locally decoded image which is independently coded in a picture and an inter-picture predicted image. For example, the present inventor first disclosed in Japanese Patent Laid-Open No. 5-130
The moving picture coding device disclosed in Japanese Patent No. 591 adaptively adds a reproduced image of intra-picture independent coding and an inter-picture predicted image to form a predicted signal.

FIG. 7 shows a block diagram of an example of a conventional moving picture coding apparatus. In the figure, all moving image signals coming from the image input terminal 1 are supplied to the frame delay device 2, while only signals to be encoded as I pictures are supplied to the DCT 20 via the switch 19. The frame delay unit 2 delays only the B picture by the frame time in order to encode the P picture prior to the B picture. The respective images whose order has been changed are given to the subtractor 3.

The image signal from the frame delay unit 2 is subtracted from a prediction signal from an adder 9 to be described later in a subtractor 3 to obtain a prediction residual, which is input to the DCT 4. DCT4
Is a discrete cosine transform (DCT: Discre
te Cosine Transform) and the obtained coefficient is supplied to the quantizer 5. The quantizer 5 quantizes the input coefficient with a predetermined step width, and supplies the coefficient having a fixed length code to the variable length encoder 6 and the inverse quantizer 10. The variable-length encoder 6 compresses the fixed-length prediction residual with a variable-length code and supplies the obtained code to the multiplexer 13.

On the other hand, the inverse quantizer 10 and the inverse DCT 11 perform the inverse processing of the DCT 4 and the quantizer 5 to reproduce the prediction residual. The obtained reproduction prediction residual is added by the adder 12 with the prediction signal from the adder 9 to form a reproduced image, which is input to the inter-image predictor 7. The inter-picture predictor 7 uses this reproduced picture as a reference picture to form an inter-picture prediction signal,
It is supplied to the multiplier 8. The multiplier 8 multiplies the reproduced image by a value of 0 to 1 in accordance with control information from the specific image setting unit 18 described later, and supplies the multiplied image to the adder 9.

The I picture is coded for some of the pictures coded as the P picture, which are set periodically. The coding of the I picture is similar to the above processing for the prediction residual, and is coded by the circuit unit including the DCT 20, the quantizer 21, and the variable length coder 22, and this processing is performed by the I (P) picture. The processing is the same as the processing of the circuit unit including the DCT 4, the quantizer 5, and the variable-length encoder 6. The obtained code is input from the variable length encoder 22 to the multiplexer 13.

On the other hand, the inverse quantizer 15 and the inverse DCT 16 perform the inverse processing of the DCT 20 and the quantizer 21 to reproduce the image. The obtained reproduced image (I-picture locally decoded image) is given to the multiplier 17. The multiplier 17 multiplies the locally decoded image by a value of 0 to 1 according to the control information from the specific image setting unit 18, which will be described later, and supplies it to the adder 9.

The adder 9 adds the inter-picture predicted image from the multiplier 8 and the I-picture locally decoded image from the multiplier 17 to obtain a final predicted image. The sum of the multiplication coefficient of the multiplier 8 and the multiplication coefficient of the multiplier 17 is 1, and may be controlled by the correlation of images. For a non-specific picture without an I picture, the multiplier 8 is 1 and the multiplier 17 is 0.
Is multiplied and the normal P picture processing is performed. Since the B picture does not serve as a reference image for prediction, this addition processing is irrelevant.

The specific image setting unit 18 sets a P picture for each predetermined period as a specific picture, and supplies its control information to the switch 19, the multipliers 8 and 17, and the multiplexer 13. The multiplexer 13 multiplexes the information of the specific picture and the code string of each picture, and outputs the information from the code string output terminal 14.

Next, a conventional moving image code sequence will be described. The conventional GOP (image group) code string configuration is a normal G
In the case of OP, as shown in FIG.
In the case of osed) GOP, it becomes as shown in FIG. In FIG. 8, delimiters indicate code strings of each picture, I, B, and P are picture types, and numbers are reproduction display picture numbers.
In the code string, it can be seen that the order of the B picture and the P (I) picture is reversed. As a result, the end of the GOP is not the P picture, but the preceding B picture.

A moving picture code string having a normal GOP structure is GO
When editing is performed in P units, the first B picture cannot be decoded. This is because the previous P picture belongs to the previous GOP and the P picture is changed to another image by editing in GOP units, so that a correct reference image cannot be obtained. In this case, in order to prevent the B-picture image from being decoded by the decoding device, it is necessary to set a flag (Bloken Link) indicating that editing is being performed.

On the other hand, since the moving picture code sequence of the closed GOP structure does not have the first B picture, the GOP
Editing in units does not affect decryption. This is because inter-picture prediction is closed by GOP, and it is not necessary to set a flag (BlokenLink) indicating that editing is being performed.

In the conventional moving picture decoding apparatus corresponding to the conventional moving picture coding apparatus shown in FIG. 7, the independent frame decoded picture and the inter-picture prediction are used in the formation of the prediction signal as in the local decoding section of FIG. This is a configuration in which images are adaptively added.

On the other hand, in a moving picture code string having a normal GOP structure, editing is performed for each GOP, and a broken link (Bl
When the "oken Link) flag is set, the B picture before the I picture after the edit point is not decoded and is replaced with the previous picture in decoding. Closed
A GOP-configured moving image code string is not affected by the code string editing in GOP units, but the P picture period becomes discontinuous, and thus a decoding process is required accordingly.

[0021]

In the conventional moving image editing, a code string group bundled in the cycle of I pictures, that is, a code string having a GOP (Group Of Picture) unit is edited, but a normal GOP structure is used. It is difficult to edit the code string, and there is no first B picture. Closed GO
In the P configuration, there are problems that the coding efficiency is lowered and the P picture period becomes discontinuous.

Further, the conventional method of having an I picture as a sub-code string in a P picture is effective for random access and the like, but the code amount is increased by the number of overlapping I pictures and the GOP corresponding to the code string editing is performed. It is not structured.

Further, the conventional method of forming a prediction signal from a locally decoded image of an I picture of the same frame and an inter-picture prediction signal has good coding efficiency, but since decoding cannot be performed without both code strings, the code is You cannot edit the column.

The present invention has been made in view of the above points,
The predetermined P picture also has an I picture, and by adding the replay images of both, the replay image can be edited to improve the image quality of the replay image. It is an object to provide a column transmission method.

[0025]

In order to achieve the above object, the moving picture coding apparatus according to the present invention uses three kinds of coding methods of independent picture, unidirectional prediction, and bidirectional prediction. A moving picture coding apparatus for coding a picture, wherein an input image signal is coded by unidirectional prediction or bidirectional prediction, and locally decoded to obtain a locally decoded image of unidirectional predictive coding.
Encoding local decoding means and a part of the picture coded by unidirectional prediction as a specific picture, and in the specific picture, unidirectional predictive coding as well as intra-picture independent coding,
Second coding local decoding means for performing local decoding to obtain a locally decoded image for intra-picture independent coding, and a locally decoded image for unidirectional predictive coding and a locally decoded image for intra-picture independent coding for a specific picture And an inter-picture prediction unit that is used as a reference image for inter-picture prediction processing of another picture.

According to the present invention, the specific picture has a picture code string that is independently coded in a picture in addition to a picture code string that is unidirectionally predictively coded, and these two types of picture code strings overlap. However, the S / N of the reproduced image can be improved by adding the locally decoded images of both.
Also, by using the reproduced image as a reference image for inter-picture prediction, inter-picture prediction efficiency can be improved.

Further, in order to achieve the above object, the moving picture coding method of the present invention uses intra-picture independent, unidirectional prediction,
In a moving picture coding method for coding each picture of a moving picture by three kinds of bidirectional prediction coding methods, an input image signal is coded by unidirectional prediction and locally decoded to locally decode the unidirectional predictive coding. The first step of obtaining an image, and a part of the picture coded by unidirectional prediction is set as a specific picture. In the specific picture, unidirectional predictive coding and intra-picture independent coding are performed, and local decoding is performed to perform intra-picture independent coding. The second step of obtaining a locally decoded image for encoding, and for a specific picture, the locally decoded image for unidirectional predictive encoding and the locally decoded image for intra-picture independent encoding are added to refer to the inter-picture prediction process for another picture. And a third step of forming an image.

According to the present invention, the specific picture has a picture code string which is unidirectionally predictively coded, and also has a picture code string which is independently coded in a picture, and these two kinds of picture code strings overlap. However, the S / N of the reproduced image can be improved by using the signal obtained by adding the locally decoded images of both as the reference image of the inter-image prediction process of another picture,
Also, by using the reproduced image as a reference image for inter-picture prediction, inter-picture prediction efficiency can be improved.

Further, in order to achieve the above object, in the code string transmission method of the present invention, each picture of a moving image is coded by three types of coding methods of intra-picture independent, unidirectional prediction and bidirectional prediction. In the method of transmitting a code string, a part of a picture coded by unidirectional prediction is set as a specific picture,
In a specific picture, there is a code string that is coded not only with unidirectional predictive coding but also with intra-picture independence. It starts with the code string that is independently coded within the picture of the specific picture, and is bidirectionally predictively coded with the picture immediately before the specific picture. It is characterized in that a code sequence ending with a code sequence is set as one code sequence group, and the code sequences synthesized in units of this code sequence group are transmitted.

According to the present invention, since the group of code strings (GOP) is divided between the unidirectional predictive coded picture included in the specific picture and the intra-picture independent coded picture, the code string is edited in GOP units. At the discontinuity point in the case of being performed, the inter-picture prediction of the other picture can be performed in the decoding device by using the unidirectional prediction coded picture as the GOP end and the intra-picture independently coded picture as the reference picture at the GOP start end.

[0031]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of an embodiment of a moving picture coding apparatus according to the present invention. In the figure, the same components as those in FIG. 7 are designated by the same reference numerals. Further, in the present specification, the “picture” refers to one frame or field.

In FIG. 1, all of the moving image signals coming from the image input terminal 1 are given to the frame delay unit 2 and only the one encoded as an I picture is switched by the switch 1.
To the DCT 20 via 9. Frame delay device 2
Delays only B pictures in order to code P pictures prior to B pictures. The respective images whose order has been changed are given to the subtractor 3.

The input image signal delayed by the frame delay unit 2 is subtracted from the prediction signal supplied from the inter-picture predictor 27 in the subtractor 3 to obtain a prediction residual, which is the DCT 4
Entered in. DCT4 is a DCT (Di
screte cosine transform), and the obtained coefficient is given to the quantizer 5. The quantizer 5 quantizes the given coefficient with a predetermined step width, and supplies the coefficient having a fixed length code to the variable length encoder 6 and the inverse quantizer 10. The variable-length encoder 6 compresses the fixed-length prediction residual from the quantizer 5 with a variable-length code, and the obtained variable-length code of the P picture or B picture is supplied to the multiplexer 13.

On the other hand, the inverse quantizer 10 and the inverse DCT 11 perform the inverse processing of the DCT 4 and the quantizer 5 to reproduce the prediction residual. The obtained reproduction prediction residual is added to the prediction signal from the inter-picture predictor 27 in the adder 12 to form a locally decoded image, which is supplied to the multiplier 25. Multiplier 25
According to the control information from the specific image setting unit 18, the locally decoded image is multiplied by a value of 0 to 1 and supplied to the adder 26.

The I picture is coded for some of the pictures coded as P pictures, which are set periodically. The coding of this I picture is performed in the same manner as the above processing for the prediction residual. That is, the I picture is input to the variable length encoder 22 through the DCT 20 and the quantizer 21 and variable length encoded. This processing is performed by the DCT 4 for the P (B) picture and the quantizer 5.
And the process of the variable length encoder 6. The variable length code of the I picture obtained by the variable length encoder 22 is input to the multiplexer 13.

On the other hand, the inverse quantizer 15 and the inverse DCT 16 perform the inverse processing of the DCT 20 and the quantizer 21 to reproduce the locally decoded image. The obtained locally decoded image is given to the multiplier 17. The multiplier 17 is a specific image setting device 18
The locally decoded image is multiplied by a value of 0 to 1 in accordance with the control information from and is supplied to the adder 26.

The adder 26 adds the two types of locally decoded images from the multipliers 25 and 17 to obtain a reference image for inter-picture prediction processing. The inter-picture predictor 27 forms an inter-picture prediction signal using this reference picture. The inter-picture prediction signal is supplied to the subtractor 3 and the adder 12, respectively.

The specific image setting unit 18 sets a P picture for each predetermined period as a specific picture, and supplies the control information to the switch 19, the multipliers 17 and 25, and the multiplexer 13.
The multiplexer 13 multiplexes the information of the specific picture and the code string of each picture, and outputs the information from the code string output terminal 14. The switch 19 is turned on only in the above-mentioned specific picture, and is turned off in the other non-specific pictures.

Next, the addition processing of the two types of locally decoded images in the adder 26 will be described. First, in the non-specific picture, since there is no I picture, the multiplier 25 multiplies 1 and the multiplier 17 multiplies 0. That is, it is the same as general P picture encoding. Since the B picture does not serve as a reference image, the addition process is not relevant in the first place.

On the other hand, in the specific picture, the multiplier 25 and the multiplier 17 both multiply the input local decoded image by a coefficient of 0.5 in order to add the locally decoded image of the P picture and the locally decoded image of the I picture. When the noise components included in the images of each other are white noise, the S / N of 3 dB can be improved by the addition, but the noise components of the locally decoded image of the P picture and I
Although the noise components of the locally decoded image of the picture have different processing methods, they have some common points such as coarse quantization at high frequency components, so that the noise components also correlate and an improvement of 3 dB cannot be obtained. . However, since they are not the same, some improvement is expected. For example, half of 1.5
If it is dB, it is necessary to increase the code amount by about 30% in order to make a corresponding improvement in the code amount.

Generally, the quality of the reproduced picture of the I picture is set higher than that of the P picture by setting the respective quantization step widths of the quantizers 5 and 21. This is a GOP
This is because improving the quality of the I picture that is the basis of the reference image of all the images contributes to improving the image quality of the entire GOP. On the other hand, when the S / N of the reproduced image of the P picture is different from that of the reproduced image of the I picture, the addition becomes less effective. Therefore, if the code amount of the I picture is reduced to some extent, the P picture and the S / N become equivalent, and the maximum effect is obtained.

In the present invention, since the P picture is added to the normal GOP structure, the code amount increases accordingly, but even if the I picture code amount is reduced and the S / N is lowered,
If the S / N of the reference image can be held by adding the I picture and the P picture, both the reproduced image and the code amount will be the same as the normal GOP.

Here, the generated code amount will be compared with the normal GOP and the closed GOP. The average code amount of I pictures is 1000 kbit, the average code amount of P pictures is 300 kbit, and the average code amount of B pictures is 100 kbit.
kbit. An image of 30 frames per second, P (I)
In the case of a normal GOP with a picture period of 3 frames,
If the GOP length is 15 frames, the average transfer rate is 6.4 Mbps from the average number of pictures in 1 second.

On the other hand, in the case of a closed GOP, the size of the GOP is different from that of the normal GOP, the GOP length is 13 frames, and the average transfer rate is 6.92 Mbp.
s, the length of GOP is 16 frames, and the average transfer rate is 6.56 Mbps, both of which increase the average transfer rate as compared with the normal GOP. Also, the GOP length is 13
Accessibility improves slightly for frames, but decreases for 16 frames. When the code amount corresponding to 15 frames is obtained from both, the code amount is 6.68 Mbps, which is a 4.4% increase in the code amount with respect to the normal GOP.

In the case of the present embodiment, if the average code amount of the I picture is the same as that of a normal GOP or closed GOP, the average transfer rate will be 7.0 Mbps, but if it is dropped by 30% to 700 kbit, the average transfer rate will be. 6.4
Mbps, which is the same as in the case of normal GOP. This is because the code amount of an I picture of a normal GOP is
It becomes the form assigned to the picture.

Next, the moving image code sequence will be described. In forming the code string encoded by the encoding device shown in FIG. 1, the P picture code string of the specific picture is the last of the GOP (image group) and the I picture is the first of the GOP. Therefore, in the specific picture, code strings are arranged in the order of P picture and I picture, and when viewed in one GOP, they start with I picture and end with P picture. The GOP configuration of this embodiment is shown in FIG.

On the other hand, since the B picture and the P (I) picture are reversed in the code string, the last picture is not the P picture but the previous B picture. That is, the formed GOP
As shown in FIG. 8C, the code sequence of the (image group) starts with the I-picture code sequence I1 which is intra-picture independently coded of the specific picture, and is bi-directional predictive coding immediately before the next specific picture. The B picture code string B15 is ended.

This GOP configuration is closed (closed) when only one GOP is compared, ignoring duplication of a specific frame.
d) Similar to GOP, if one of the I picture and P picture is deleted in a specific frame, the structure of GOP changes depending on the deleted one, but the order of pictures is normally G
It becomes the same as the arrangement of OPs. That is, G of the present embodiment
An OP can combine the properties of both a closed GOP and a normal GOP.

The moving picture code string is a closed
d) The code string can be edited in GOP units as in the case of GOP. The situation is shown in FIG. As shown in the figure, 1 GOP of the code string B shown in the 3rd row is inserted between GOPs having the code string A shown in the 1st row and GOP 2
An edited code string as shown in the row is obtained. Here, the beginning and the end of each GOP are duplicate pictures. Therefore, the processing is different from that of the conventional editing apparatus.

First, regarding the image length, the editing time is calculated without incorporating the last P picture of the GOP into the length (time) of the GOP. Therefore, even if the code string of the GOP structure of this embodiment is 16 frames, it is regarded as 15 frames.

Next, the GOP is controlled by the reproduction control of the specific picture.
When editing is performed in units, both the P picture of the previous GOP and the I picture of the subsequent GOP can be decoded and reproduced as the specific picture serving as the edit point. On the other hand, the contents of the image are different because the image is being edited. As a method of positively utilizing the point where the code strings overlap, by editing the image to be output at the time of reproduction or by including the control information, the edit point can be moved forward or backward by one picture with the same code string.

Further, in the conventional closed GOP, since there is no processing change in the decoding device, it is not necessary to set a flag (Bloken Link) indicating that editing is being performed, but in this method, decoding is performed. Since it is necessary to switch processing, it is necessary to set a broken link (Bloken Link) flag.

Next, each example of the moving picture decoding apparatus will be described. FIG. 3 shows a block diagram of an example of the moving picture decoding apparatus. This moving picture decoding apparatus shows the structure of a decoding apparatus corresponding to the embodiment of the moving picture coding apparatus of the present invention shown in FIG. 1, which is the image continuity that is not edited. This is the case of a code string in which

In FIG. 3, the code string coming from the code string input terminal 31 is separated by the demultiplexer 32 into a code string of the I picture and a code string other than the I picture based on the header of the picture. The code strings of P pictures and B pictures are supplied to the variable length decoder 33, and the code strings of I pictures are supplied to the variable length decoder 34.

In the code string of the P (B) picture, the variable length code of the prediction residual is returned to the fixed length code by the variable length decoder 33 and supplied to the inverse quantizer 35. The inverse quantizer 35 is
The input fixed-length code is inversely quantized according to the quantization parameter to obtain a reproduced residual DCT coefficient value of the prediction residual, and this is supplied to the inverse DCT 36.

The inverse DCT 36 converts the 8 × 8 coefficients into a decoded prediction residual signal and supplies it to the adder 37. Adder 37
Adds the prediction signal given from the inter-picture predictor 45 to the above-mentioned decoded prediction residual signal to obtain a decoded image signal. The decoded image signal of the P (B) picture obtained in this way is
It is supplied to the multiplier 42.

On the other hand, the code string of the I picture separated by the demultiplexer 32 is decoded by the variable length decoder 34,
After being inversely quantized by the inverse quantizer 38, decoded by the inverse DCT 39 to be a reproduced image signal, it is inputted to the multiplier 41. Variable length decoder 34, inverse quantizer 38, inverse DCT3
The operation of 9 is the same as that of the variable length decoder 33, the inverse quantizer 35, and the inverse DCT 36, but the parameters are those for the I picture.

Further, the demultiplexer 32 detects the picture ID from the picture header in the input code string, and the result information is supplied to the specific image controller 40. The specific image controller 40 detects a specific picture and supplies the control information to the multipliers 41 and 42, respectively. Multiplier 41
According to the above control information, the reproduced image signal from the inverse DCT 39 is multiplied by a value of 0 to 1 and given to the adder 43.
On the other hand, the multiplier 42 adds the adder 3 according to the above control information.
The decoded image signal of the P (B) picture from 7 is multiplied by a value of 0 to 1 and given to the adder 43.

The adder 43 adds the two types of decoded image signals extracted from the multipliers 41 and 42 to obtain a reproduced image signal. The addition by the adder 43 is performed only for a specific picture, and at this time, both the multiplier 41 and the multiplier 42 have coefficients of 0.
It is multiplied by 5. Otherwise, the multiplier 42 multiplies the coefficient 1 by the decoded image signal, and the multiplier 41 multiplies the coefficient 0 by the decoded image signal. Therefore, the adder 43 outputs P (P) from the adder 37. B) The decoded image signal of the picture is output as it is.

In the specific picture, the reproduced image signal is added by the adder 4
By the addition in 3, the S / N is improved from the decoded image signals extracted from the multipliers 41 and 42. The state of such decoding is shown in FIG.

The reproduced image signal output from the adder 43 is directly output from the reproduced image output terminal 47 via the switch 46 for the B picture. On the other hand, the reproduced image signal output from the adder 43 is temporarily stored in the image memory 44 in the P (I) picture, is used as a reference image for inter-picture prediction processing, and is delayed, and then inter-picture prediction is performed. It is supplied to the adder 22, where it is used as a prediction signal using this reference image and is input to the adder 37. Switch 46
Selects the delayed B picture and the delayed P (I) picture in the image memory 44 and outputs them to the output terminal 47.

Next, another example of the moving picture decoding apparatus will be described. FIG. 5 shows a block diagram of another example of a moving picture decoding apparatus corresponding to the moving picture coding apparatus of FIG. In FIG.
The same components as those in FIG. 3 are designated by the same reference numerals, and the description thereof will be omitted. The decoding device of FIG. 5 is a device that performs decoding when the code string is edited and image continuity is not maintained.

The decoded picture signal of the B picture output from the adder 37 is directly output from the reproduction picture output terminal 47 via the switch 51. On the other hand, the decoded image signal of the P picture output from the adder 37 is the image memory 48.
Once held. Further, the decoded image signal of the I picture output from the inverse DCT 39 is temporarily held in the image memory 49.

Since the GOP is being edited, the P picture and I picture of the specific picture are formally the same picture, but the P picture is that of the previous GOP and the I picture is after. Of the GOP. Therefore, the switch 50 switches the two from the image memories 48 and 49.
An appropriate one is selected as a reference image from the types of decoded image signals as follows.

Next to the decoding of the specific picture, the previous GOP
The B picture is decoded, and the decoded picture of the P picture held in the picture memory 48 is selected. Subsequently, in the decoding of the P picture and B picture of the next GOP, the decoded image of the I picture held in the image memory 49 is selected. The state of decoding in this case is shown in FIG. In the figure, the arrow indicates the inter-image prediction relationship.

In the decoding of the decoding device shown in FIG. 5, the reference image for inter-picture prediction is slightly different from the reference image of the encoding device, but both are decoded images for the same image and the quantization noise The original images other than the components are common. The change in the reference image affects only two pictures immediately before the edit point and 1 GOP after the edit point. However, since the prediction residual components are sequentially added after the editing point, the influence of the reference image change gradually decreases. On the other hand, considering the visual characteristics, it is said that when the scene is changed by editing, the deterioration is hardly noticed, and the detection ability is greatly reduced for about 0.1 seconds immediately after the change. Therefore, the visual impact of degradation is very small.

The reproduction image output is selected by the switch 51. The operation of the switch 51 is the same as the switch 46 of FIG. 3 except for a specific picture. Since it is possible to output either an I-picture or a P-picture in a specific frame, it may be decided in advance which one to select, but the code string editing apparatus stores control information in the code string. If so, control accordingly.

Although the moving picture coding apparatus and method have been described in the above embodiments, the present invention is not limited to this, and a part of a picture coded by unidirectional prediction is specified. As a picture, there is a code string that is coded by unidirectional predictive coding as well as intra-picture independent coding, and bidirectional prediction of the picture immediately before the specific picture starts with the code string that is independently coded within the picture of the specific picture. A code string ending with the coded code string may be set as one code string group, and the code string combined in units of this code string group may be transmitted via a desired transmission path.

[0069]

As described above, according to the present invention,
In a specific picture, in addition to a picture code string that has been unidirectionally predictively coded, it also has a picture code string that has been independently coded within a picture, and these two types of picture code strings will overlap. Since the S / N of the reproduced image is improved by adding, the image quality of the reproduced image can be improved. Further, since the reproduced image is used as the reference image for inter-picture prediction, the inter-picture prediction efficiency is also improved, so that the total code amount can be reduced correspondingly in the specific picture.

Further, according to the present invention, a group of code strings (GO
P) By dividing the unidirectional predictive coded picture included in the specific picture and the intra-picture independent coded picture, the decoding is performed at the discontinuous points when the code string is edited in GOP units. Since the GOP end uses the unidirectional predictive coded picture at the GOP end and the intra-picture independent coded picture as the reference image at the GOP start end, inter-picture prediction of other pictures is performed, so that the unidirectional predictive efficiency is the same as that of normal GOP. While maintaining the periodicity of the predictive-coded picture, it is possible to generate a code string capable of editing the code string in GOP units as in the case of the closed GOP.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a moving image encoding apparatus of the present invention.

FIG. 2 is a diagram illustrating an example of how a moving image code string is edited.

FIG. 3 is a block diagram of an example of a moving image decoding apparatus.

[Fig. 4] Fig. 4 is a diagram illustrating each example of decoding in picture units.

FIG. 5 is a block diagram of another example of a moving picture decoding apparatus.

FIG. 6 is a diagram showing each example of a GOP configuration.

FIG. 7 is a block diagram of an example of a conventional moving image encoding device.

[Fig. 8] Fig. 8 is a diagram illustrating an example of a GOP (image group) code string configuration.

[Explanation of symbols]

1 Image input terminal 2 frame delay 3 subtractor 4, 20 DCT 5,21 quantizer 6,22 Variable length encoder 10, 15, 35, 38 Dequantizer 11, 16, 36, 39 Inverse DCT 12, 26, 37, 43 Adder 13 Multiplexer 14 Code string output terminal 17, 25, 41, 42 Multiplier 18 Specific image setting device 19,46 switch 27,45 Inter-picture predictor 31 Code string input terminal 32 demultiplexer 33, 34 variable length decoder 40 Specific image controller 47 Playback image output terminal

Continued front page    F-term (reference) 5C053 FA14 GA11 GB06 GB17 GB21                       GB22 GB26 GB29 GB32 GB37                       KA09 KA22                 5C059 KK01 KK36 MA23 MC11 ME01                       PP05 PP06 PP07 TA25 TA31                       TB03 TC03 UA02                 5J064 AA02 BA09 BA16 BB01 BB03                       BC02 BC08 BC09 BD01

Claims (3)

[Claims] 1. A moving picture coding apparatus for coding each picture of a moving picture by three types of coding methods: intra-picture independent, unidirectional prediction, and bidirectional prediction. First encoding local decoding means for obtaining a locally-decoded image of unidirectional prediction encoding by locally decoding with directional prediction, and a part of the picture encoded by the unidirectional prediction as a specific picture, In the specific picture, the unidirectional predictive coding is performed together with the intra-picture independent coding, and the local decoding is performed.
Second encoding local decoding means for obtaining a locally decoded image of intra-picture independent encoding, and adding the locally decoded image of the unidirectional predictive coding and the locally decoded image of the intra-picture independent encoding in the specific picture Then, the moving picture coding apparatus is characterized in that it has inter-picture predicting means which is used as a reference picture for inter-picture prediction processing of other pictures. 2. A moving picture coding method for coding each picture of a moving picture by three kinds of coding methods of intra-picture independent, unidirectional prediction and bidirectional prediction, wherein an input image signal is coded by the unidirectional prediction. Of the pictures to be locally decoded and locally decoded to obtain a locally decoded image of unidirectional predictive coding, and a part of the picture coded in the unidirectional prediction is set as a specific picture, and the unidirectional predictive coding is performed in the specific picture. A second step of obtaining the locally decoded image of the intra-picture independent coding by performing local decoding with the intra-picture independence, and the locally decoded image of the unidirectional predictive coding and the intra-picture independent in the specific picture A third step of adding locally decoded images for encoding to obtain a reference image for inter-picture prediction processing of another picture, the moving image encoding method. 3. A method for transmitting a code string in which each picture of a moving image is coded by three types of coding methods of intra-picture independent, unidirectional prediction, and bidirectional prediction, wherein the unidirectional prediction is used for coding. A part of the picture is a specific picture, and in the specific picture, there is a code string that is encoded in the picture independent with the unidirectional predictive coding, and starts with a code string that is independently coded in the picture of the specific picture. A code characterized in that a code string ending with a bidirectional predictive coded code string of a picture immediately before the specific picture is set as one code string group, and the code string synthesized in units of this code string group is transmitted. Column transmission method.