JPH0683443B2 - Intra-frame interframe coding method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of use] The present invention relates to an intraframe interframe code in which a coding efficiency is prevented from being deteriorated by a scene change in a system for band-compressing and transmitting an image signal. It is related to the conversion method.

[Conventional technology]

As a method of band-compressing and transmitting an image signal, either one of an intra-frame coding method using correlation between pixels or an inter-frame coding method using correlation between frames, or a composite coding combining both The scheme is known. For example, FIG. 3 is a block diagram of a conventional example, showing a main part for performing interframe composite encoding, and illustration of an encoder, a buffer memory, etc. is omitted. The digitized image signal is input to the input terminal 21, and the subtracter 22 obtains the difference from the inter-frame predicted value corresponding to the image signal of the previous frame read from the frame memory 29, and the subtractor 22 Is output to a subtracter 23 for performing intra-frame encoding, and a quantizer 24 calculates the difference from the intra-frame prediction value corresponding to the image signal read from the memory 27 before the predetermined number of pixels. Added to.

The quantized output signal from the quantizer 24 corresponds to the prediction error signal, and is added to the encoder (not shown) from the output terminal 25 and converted into a variable length code. Therefore, the intra-frame difference and the inter-frame difference are coded. For example, in the case of a monotonous screen, the intra-frame difference becomes small, and the coding efficiency becomes high only by the intra-frame coding. Further, when the current screen and the previous screen are the same, the inter-frame difference becomes zero, so that the inter-frame coding alone increases the coding efficiency.

The quantized output signal from the quantizer 24 is added to an adder 26, which is added to the intra-frame prediction value by the adder 26 and is stored in the memory 27 as the next intra-frame prediction value and is also added to the adder 28. The added value is added to the inter-frame predicted value in the adder 28, added to the frame memory 29, and stored as the inter-frame predicted value of the next frame.

Further, in order to reduce the inter-frame difference value when a part of the screen is shifted, the direction and magnitude of the screen movement are detected, and the inter-frame prediction value read control from the frame memory 29 is controlled. A method of providing a motion compensation function is also known.

[Problems to be solved by the invention]

In the case of a still screen, the inter-frame difference value becomes zero or a value close to zero over the entire one frame as described above. However, when image signals from a plurality of TV cameras are switched, In a scene change such as when the imaging range or the direction is suddenly changed, the inter-frame difference value becomes a very large value. As a result, the coding efficiency is lowered.

It is an object of the present invention to prevent the coding efficiency from decreasing even when the inter-frame difference value due to a scene change or the like becomes large.

[Means for solving problems]

The intra-frame inter-frame coding method of the present invention will be described with reference to the drawings by referring to the subtracter 3, the memory 7, the first selector 10
And the like, and an encoding means having an intra-frame encoder including the subtractor 2, the frame memory 9, the second selector 11 and the like, an input signal and a delay circuit 12 including the input signal. By comparing the intra-frame correlation value of the correlation between the signal delayed by a predetermined number of pixels with the inter-frame correlation value of the correlation between the input signal and the inter-frame prediction value, the intra-frame correlation value and the inter-frame correlation value are compared. First, determine the magnitude relationship with the value
A determining unit 15 for controlling the second selectors 10 and 11 is provided, and the determining unit 15 causes the second selector 11 to select and output a constant value when the intra-frame correlation value is larger. The intra-frame prediction value is selectively output from the selector 10 to perform intra-frame coding, and when the inter-frame correlation value is larger, the first selector 10 selectively outputs a constant value, and the second selector 11 Switching is performed so that interframe prediction values are selectively output and interframe coding is performed.

Also, the intra-frame correlation value and the inter-frame correlation value including the inter-frame / intra-frame correlation value of the correlation between the difference value between the input signal and the inter-frame prediction value and the signal obtained by delaying the difference value by the predetermined number of pixels If the intra-frame correlation value is maximum, switch to intra-frame coding as described above, and if the inter-frame correlation value is maximum, switch to inter-frame coding as described above. When the inter-frame / intra-frame correlation value is maximum, the intra-frame predicted value is selected and output from the first selector 10 and the inter-frame predicted value is selectively output from the second selector 11. Switch so that inter-coding is performed.

[Action]

The encoding means includes an intra-frame encoding unit and an inter-frame encoding unit, and the intra-frame encoding unit includes the subtracter 3, the memory 7,
The configuration includes the first selector 10 and the like, and the interframe coding unit includes a subtractor 2, a frame memory 9, and a second selector 11
It is a configuration including the above. And at the scene change,
The intra-frame correlation value is larger than the inter-frame correlation value. At that time, a constant value is selectively output from the second selector 11 to stop interframe coding, and an intraframe correlation value is selectively output from the first selector 10 to perform intraframe coding. In the normal case, the interframe correlation value is often larger than the intraframe correlation value,
At that time, a fixed value is selectively output from the first selector 10 to stop the intra-frame coding, and the second selector
The interframe prediction value is selected and output from 11, and interframe coding is performed.

Also, the inter-frame / intra-frame correlation value of the correlation between the difference value between the input signal and the frame prediction value and the signal obtained by delaying the difference value by the predetermined number of pixels is obtained. The intraframe correlation value and the interframe correlation value described above are compared, and if the intraframe correlation value is the maximum, the intraframe coding is performed as described above. If the interframe correlation value is the maximum, Inter-frame coding is performed as described above, and when the inter-frame / intra-frame correlation value is the maximum, the intra-frame predicted value is selectively output from the first selector 10, and the inter-frame prediction value is output from the second selector 11. The predicted value is selectively output, and composite coding of intraframe coding and interframe coding is performed.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a block diagram of an embodiment of the present invention, in which 1 is an input terminal of a digitized image input signal a, 2 and 3 are subtractors, 4 is a quantizer, 5 is an output terminal, and 6, 8 is adder, 7
Is a memory for accumulating the intra-frame prediction value g, 9 is a frame memory for accumulating the inter-frame prediction value d, 11 is a subtracter 2 and an adder 8 by switching between the inter-frame prediction value d and a constant value e such as 0. A second selector 10 for adding to the subtractor 3 for switching between the intra-frame predicted value g and a constant value h such as 0
Selector, 12 is a delay circuit having a delay time of a predetermined number of pixels, 13 and 14 are subtractors, and 15 is output signals b and c of the subtracters 13 and 14.
Is an output terminal for the determination signal f, and the encoder is not shown.

The input signal a and the signal obtained by delaying the input signal a by a predetermined number of pixels by the delay circuit 12 are added to the subtractor 13, and the output signal b thereof shows the correlation between pixels corresponding to the number of delayed pixels. That is, the output signal b of the subtractor 13 becomes the intra-frame correlation value. Further, the input signal a and the inter-frame predicted value d read from the frame memory 9 are added to the subtractor 14, and the output signal c thereof shows the difference between the frames. That is, the output signal c of the subtractor 14 has a value obtained by inverting the interframe correlation value.

The determination unit 15 compares the magnitudes of the output signals b and c of the subtracters 13 and 14 for each block unit of m lines × n pixels, and compares which of the output signals b and c has a strong correlation with the input signal a. To output the determination signal f. The determination signal f is transferred from the output terminal 16 to an encoder or a transmission unit (not shown) for transmission to the receiving side as information indicating intra-frame encoding or inter-frame encoding.

The selector 10 is controlled by the judgment signal f, and when the constant value h such as 0 is selectively output, the subtractor 3 subtracts 0, so that the intra-frame coding is not performed and the selector 7 reads from the memory 7. When the selected intra-frame prediction value g is selectively output, the intra-frame difference is obtained by the subtractor 3, and thus intra-frame encoding is performed. Further, when the selector 11 is also controlled by the judgment signal f and a constant value e such as 0 is selectively output, the subtractor 2 subtracts 0, so that the interframe coding is not performed and the frame memory 9
When the inter-frame predicted value d read from is selected and output, the inter-frame difference is obtained by the subtractor 2, so inter-frame coding is performed.

In the case of a scene change, the screens before and after the scene change are largely different, so that the inter-frame correlation becomes smaller and the intra-frame correlation becomes larger. Therefore, since the output signal c of the subtractor 14 is larger than the output signal b of the subtractor 13 in one block period, the determination unit 15 outputs the determination signal f determined to have a large intra-frame correlation. Become.
As a result, the selector 10 selectively outputs the intra-frame predicted value g, and the selector 11 selectively outputs the constant value e, so that the inter-frame encoding is not performed and the intra-frame encoding is performed.

After the scene change, the correlation between the inter-frame predicted value sequentially written in the frame memory 9 and the received signal a of the next frame gradually increases. Therefore, after several frames, the inter-frame correlation is larger than the intra-frame correlation. Become. Particularly in the case of a still screen, the inter-frame correlation rapidly increases. When the determination unit 15 determines that such inter-frame correlation has increased, the determination signal f indicates the selector 10
Will output a constant value h, and intra-frame coding will not be performed. Since the selector 11 selectively outputs the inter-frame predicted value d from the frame memory 9,
Interframe coding will be performed.

As described above, when inter-frame coding is performed at the scene change, the coding efficiency is reduced. However, since the present invention is switched to the intra-frame coding, the coding efficiency is not lowered. Further, in the steady state, especially in the case of a still screen, the coding efficiency can be improved by the interframe coding rather than the intraframe coding. Also, the determination signal f is sent to the receiving side to notify it of whether the signal is a signal by intra-frame coding or a signal by inter-frame coding.

FIG. 2 is a block diagram of another embodiment of the present invention, showing an embodiment for performing intra-frame coding, inter-frame coding and inter-frame composite coding. In the figure, the same reference numerals as those in FIG. 1 indicate the same parts, and 16a and 16b are the judgment signals f.
1, f2 output terminals, 17 a determination unit, 18 a delay circuit, and 19 a subtractor. The subtractor 14 obtains the difference value between the input signal a and the inter-frame predicted value d read from the frame memory 9, and the difference value signal c is delayed by the delay circuit 18 by a predetermined number of pixels to obtain the difference value signal. c and the delayed signal are added to the subtractor 19, and the output signal i of the subtractor 19 indicates the interframe / intraframe correlation value.

The determination unit 17 is configured to add the output signals b, c, i of the subtracters 13, 14, 19 to determine the magnitude relationship between the intraframe correlation value, the interframe correlation value, and the interframe / intraframe correlation value. And has a comparator, an accumulator, and the like. In this judging section 17, the signals b, c,
By comparing i, a scene change is determined when the intra-frame correlation value is the largest, a still screen is determined when the inter-frame correlation value is the highest, and a normal screen is determined when the inter-frame / intra-frame correlation value is the highest. It is a thing.

The selector 10 causes the memory 7 to operate according to the determination signals f1 and f2 when the determination unit 17 determines that the intra-frame correlation value is the largest.
The intra-frame predicted value g read out from is selectively output, and the selector 11 selectively outputs the constant value e. Thereby, inter-frame coding is not performed, but only intra-frame coding is performed. That is, at the time of a sea change where the inter-frame correlation is small, the intra-frame coding is not performed and only the intra-frame coding is performed, so that it is possible to prevent a decrease in the coding efficiency.

Further, the selector 10 selectively outputs the constant value h by the determination signals f1 and f2 when it is determined that the inter-frame correlation value is the largest, and the selector 11 selects the inter-frame predicted value d read from the frame memory 9. Output. Thereby, intraframe coding is not performed, but only interframe coding is performed. That is, in the case of a still screen, the inter-frame difference becomes zero, so that it is possible to improve the coding efficiency only by inter-frame coding.

Further, the selector 10 selectively outputs the intra-frame predicted value g read from the memory 7 according to the determination signals f1 and f2 when it is determined that the inter-previous-frame / intra-frame correlation value is the largest, and the selector 11 selects the frame memory 9 The inter-frame predicted value d read from is selected and output. As a result, inter-frame composite encoding that performs both intra-frame encoding and inter-frame encoding is performed. That is, it is possible to improve the coding efficiency for a screen with normal movement.

The determination signals f1 and f2 are sent to the receiving side as information indicating which of the intra-frame coding, the inter-frame coding, and the inter-frame composite coding has coded the image signal.

〔The invention's effect〕

As described above, the first invention is the first selector 10
And an input signal a and this input signal a are delayed by a delay circuit 12 or the like by a predetermined number of pixels. A determination unit 15 is provided that compares the intra-frame correlation value of the correlation with the signal and the inter-frame correlation value of the correlation between the input signal a and the inter-frame predicted value d to determine the magnitude relationship between them. When the determination unit 15 determines that the intra-frame correlation value is large, it switches to intra-frame coding, and when the inter-frame correlation value is determined to be large, it switches to inter-frame coding. And the inter-frame correlation value, the determination unit 15 can easily determine whether or not the screen has a large change such as a scene change. At the scene change, the inter-frame correlation is small. By changing the encoding means so that only encoding is performed, it is possible to prevent a decrease in encoding efficiency.

The second aspect of the present invention further includes an interframe prediction value d and an input signal a.
And the inter-frame / intra-frame correlation value obtained by correlating the difference value between the signal and
In addition to 17, determine the correlation value of the maximum value, switch to intraframe coding when the intraframe correlation value is maximum, switch to interframe coding when the interframe correlation value is maximum,
When the inter-frame / intra-frame correlation value is the maximum, it switches to inter-frame composite encoding, and it is possible to improve the encoding efficiency by using composite encoding for a screen with normal movement. When the inter-frame correlation value becomes small, it is possible to switch to intra-frame coding and prevent the coding efficiency from decreasing. Furthermore, each coding method is such that the first and second selectors 10 and 11 are used in the determination unit 1.
There is an advantage that switching can be easily performed by controlling with 5,17.

[Brief description of drawings]

1 and 2 are block diagrams of different embodiments of the present invention, and FIG. 3 is a block diagram of a conventional example. 1 is an input terminal, 2 is a subtractor, 4 is a quantizer, 5 is an output terminal, 6 is an adder, 7 is a memory for accumulating an intra-frame prediction value g, and 9 is an inter-frame prediction value d. Frame memory to store, 10, 11 selectors, 12, 18 delay circuits, 13, 14, 19
Is a subtracter, and 15 and 17 are decision units.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Yutaka Fukuda, 1015 Kamiodanaka, Nakahara-ku, Kawasaki-shi, Kanagawa, Fujitsu Limited (72) Inventor Ken Okazaki, 1015, Kamikodanaka, Nakahara-ku, Kawasaki, Kanagawa, Fujitsu Limited ( 72) Inventor Shinichi Maki 1015 Kamiodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture, Fujitsu Limited (72) Inventor Takashi Ito 1015, Kamikodanaka, Nakahara-ku, Kawasaki City, Kanagawa Prefecture Fujitsu Limited (72) Inventor, Osamu Kawai Kanagawa 1015 Kamiodanaka, Nakahara-ku, Kawasaki Prefecture, Japan, within Fujitsu Limited (56) References JP-A-53-52013 (JP, A) JP-A-49-24019 (JP, A)

Claims (2)

[Claims] 1. An intraframe coding unit including a first selector for selecting an intraframe prediction value and a constant value, and an interframe coding including a second selector for selecting an interframe prediction value and a constant value. An intra-frame correlation value of a correlation between an input signal and a signal obtained by delaying the input signal by a predetermined number of pixels, and a correlation between the input signal and the inter-frame predicted value. And a determination unit that compares the inter-frame correlation value and determines the magnitude relationship between the intra-frame correlation value and the inter-frame correlation value to control the first and second selectors. When it is determined that the intra-frame correlation value is larger, the second selector selectively outputs the constant value and the first selector selectively outputs the intra-frame predicted value to perform intra-frame encoding. Let it be done between the frames When it is determined that the correlation value is larger, the constant value is selectively output from the first selector, and the interframe prediction value is selectively output from the second selector to perform interframe coding. An interframe coding method characterized by switching. 2. An intraframe coding unit including a first selector for selecting an intraframe prediction value and a constant value, and an interframe coding including a second selector for selecting an interframe prediction value and a constant value. An intra-frame correlation value of a correlation between an input signal and a signal obtained by delaying the input signal by a predetermined number of pixels, and a correlation between the input signal and the inter-frame predicted value. The inter-frame correlation value, the inter-frame / intra-frame correlation value of the correlation between the difference value between the input signal and the inter-frame predicted value and the signal obtained by delaying the difference value by the predetermined number of pixels are compared, And a determination unit that controls the first and second selectors by determining the magnitude relationship among the intra-frame correlation value, the inter-frame correlation value, and the inter-frame / intra-frame correlation value. When the intra-frame correlation value is maximum, the The second selector selects and outputs the fixed value, and the first selector selects and outputs the intra-frame predicted value to perform intra-frame coding. When the inter-frame correlation value is maximum, the first The selector outputs the fixed value and the second selector outputs the inter-frame prediction value to perform inter-frame coding. When the inter-frame / intra-frame correlation value is maximum, the first
Select and output the intra-frame prediction value from the selector of
In addition, an intraframe interframe coding method is characterized in that the interframe prediction value is selectively output from the second selector and switched so as to perform intraframe interframe coding.