JPH03214988A - Moving compensation inter-frame coder - Google Patents

Abstract

PURPOSE:To improve picture quality by checking whether or not a moving vector is identical to surrounding adjacent blocks whose movement is compensated and applying movement compensation even to a block decided for non movement compensation when a coded block is a block in the center in the occurrence of panning. CONSTITUTION:A 2nd movement compensation decision section 8 stores a moving vector 6 of a coded block and a 1st movement compensation control signal 7 to judge whether or not the movement compensation is valid as to the coding block finally and the result is outputted as a 2nd movement compensation control signal 12. In this case, the 2nd movement compensation decision section 8 compares a moving vector of the coded block 6 with movement vectors of its adjacent surrounding blocks. When both the vectors are identical, even a block decided for non movement compensation is subjected to movement compensation. Thus, the deterioration in the picture quality caused due to mixture of blocks subject to movement compensation and blocks subject to no movement compensation at a flat part of the screen at the parallel movement of the entire pattern is prevented and the picture quality is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a motion compensated interframe coding device for television signals.

BACKGROUND OF THE INVENTION In recent years, with the development of video encoding technology, motion compensated predictive interframe coding has been developed as a high-efficiency encoding device for color video images used in video telephones, video conference systems, C[)-4tOM, digital VTRs, etc. equipment has been developed. For example, Multidimensional Signal Processing of rI'V Images J by Takahiko Fukinuki (November 15, 1988, Nikkan Kogyo Shimbunsha, Chapter 7 High Efficiency Coding, pp213-pp291)
) is known as a motion compensated predictive interframe coding device.

Although the motion compensated predictive interframe coding method can achieve high coding efficiency, it has the following problems.

Whether or not to perform motion compensation is determined by the following: 1. The difference between the pixel value of the encoded block and the predicted pixel value of the encoded block is used for motion compensation. 2. The difference between the pixel value of the encoded block and the pixel value of the previous frame is used for motion compensation. It is determined that

Therefore, according to (1) and (2), in a part where there are many blocks where a determination is made near the boundary whether or not to perform motion compensation, blocks that are motion compensated and blocks that are not motion compensated coexist. In particular, parallel movement (panning) of the entire screen whose size exceeds a certain value
ing ), if there is a block that is not motion compensated and is surrounded by blocks that are motion compensated in a flat area on the screen, this will cause deterioration in image quality.

Hereinafter, a conventional motion compensated interframe coding device will be explained with reference to FIG. In FIG. 3, 41 is an input terminal into which an input television signal is input, and 43 is a unit that compares the picture signal of the coded block of the current frame with the reproduced picture signal of the previous frame to calculate the motion vector of the coded block. 44 is an image memory unit that stores the reproduced image signals of the current frame and the previous frame; 48 is a motion compensation unit that performs motion compensation for the reproduced image signal of the previous frame; An in-loop filter section performs dimensional low-pass filter processing; 52 is a prediction error calculation section that calculates a prediction error by calculating the difference between the original image signal and the prediction signal of the encoded block; and 54 is an orthogonal transformation section that orthogonally transforms the prediction error signal. , 56 is a quantization unit that quantizes orthogonal transform coefficients, 59 is an inverse orthogonal transform unit that performs inverse orthogonal transform on the quantized orthogonal transform coefficients, 6l is a reproduced image calculation unit that calculates a reproduced image of the current frame, and 63 is a prediction unit. 65 is a motion vector encoding unit that encodes a motion vector through a channel, 67 is a multiplexer unit that configures a transmission frame from a prediction code and a motion vector code, and 69 is a transmission frame. The code memory section 71 is an output terminal for outputting a transmission signal.The operation of the above-described configuration will be explained below. It is converted into a digital signal by an analog-to-digital conversion circuit (not shown), and is divided into N pixels in the horizontal direction and N pixels in the vertical direction.
The television signal divided into blocks of lines is input as an input television signal 42 through an input terminal 41 . The motion vector calculation section 43 compares the input television signal 42 with the reproduced television signal 45 of the previous frame stored in the image failure memory section 44, calculates the motion of the encoded block as a motion vector, and generates a motion vector signal. 46
Output to. At the same time, the motion vector calculation unit 43 uses the evaluation value at the time of motion vector calculation to determine whether motion compensation is valid or invalid for the encoded block, and outputs the result as a motion compensation control signal to the motion vector signal 46. Therefore, the motion vector signal 46 has a motion vector and a motion compensation signal superimposed thereon. The motion compensation unit 48 Q) motion-compensates the reproduced television signal 45 of the previous frame using a motion vector when the motion compensation control signal indicates that motion compensation is valid; If invalidation of compensation is instructed, the reproduced television signal 45 of the previous frame is output as is as a motion compensation signal 49.

The in-loop filter section 50 performs two-dimensional low-pass filter processing on the encoded block motion-compensated using the motion vector, and outputs it as a prediction signal 51.

The prediction error calculation unit 52 performs a difference calculation between the input television signal 42 of the encoded block and the prediction signal 51, and outputs the result as a prediction error signal 53. Orthogonal transformation unit 5
4 performs orthogonal transformation on the prediction error signal 53, removes high correlation between neighboring pixels of the prediction error signal 53, and calculates the prediction error orthogonal transformation coefficient 55. As the orthogonal transform method, in many cases, discrete cosine transform is used, which has high transform efficiency and can be implemented in hardware. The quantizer 56 is a quantizer whose quantization characteristics change depending on the generated code amount 57, and the prediction error orthogonal transform coefficient 5
5 is quantized, and a prediction error orthogonal transform quantization coefficient 58 is calculated. Inverse orthogonal transform unit 59? "i, Prediction Error Orthogonal Transformation The quantization coefficient 58 is inverse orthogonal transformed to calculate a prediction error signal 60 including a quantization error. The reproduced image calculation unit 6l converts the prediction error signal 60 including a quantization error and the prediction signal Add 51,
A reproduced image 62 of the encoded block is calculated. The image memory 44 stores the reproduced image signal 62 of the current frame and outputs the reproduced image signal 45 of the previous frame.

The prediction error encoding unit 63 generates the prediction error orthogonal transform quantization coefficient 5.
8 is encoded, and a prediction error code 64 is calculated. The motion vector encoding unit 65 encodes the motion vector 46 and calculates a motion vector code 66. The multiplexer unit 67 calculates a transmission frame 68 in a predetermined format from the prediction error code 64 and the motion vector code 66. The code memory unit 69 temporarily stores the transmission frame 68 and outputs it as a transmission code 7o through the output terminal 7l in synchronization with a clock signal inputted from an external device (not shown).

Problems to be Solved by the Invention However, in the above configuration, whether or not to perform motion compensation depends on the prediction error value and the difference value between the encoded block and the previous frame. Therefore, in areas where there are many blocks where a determination is made near the boundary of whether or not to perform motion compensation based on these two values, there may be a mixture of blocks that are motion compensated and blocks that are not motion compensated. become. Parallel movement (panning) of the entire screen with a size greater than a certain value
ng), etc., if there is a block that is not motion compensated and is surrounded by blocks that are motion compensated in a flat area on the screen, this will cause image quality deterioration.

In view of the above-mentioned problems, the present invention examines whether the motion vector of a block that is not motion-compensated using the conventional method is the same as the motion vector of neighboring adjacent motion-compensated blocks. If the block is in the center of the block, the purpose is to correct the determination that motion compensation is not to be performed, perform motion compensation, and improve image quality.

Means for Solving the Problems The technical solution of the present invention to achieve the above object is a means for converting a television signal from analog to digital;
means for dividing one frame or one field of a digitized input television signal into blocks of a predetermined size; means for calculating a motion vector representing the movement of a television image for each block; and an inter-frame difference value. a first motion compensation determination means that determines whether or not motion compensation is to be performed on the encoded block based on the motion compensation and calculates the result as a motion compensation control signal; A means for accumulating motion vectors of surrounding blocks and motion compensation control signals, and a motion vector of an encoded block determined not to undergo motion compensation by the first motion compensation determination means and surroundings adjacent to the encoded block. a motion compensation control signal correction means for comparing the motion vectors of the blocks, and changing the motion compensation control signal to perform motion compensation when the number of blocks whose motion vectors can be considered to match is K or more; means for calculating a difference between a pixel value of a block and a predicted pixel value based on the corrected motion compensation control signal as a prediction error value; and means for orthogonally transforming the prediction error value and calculating an orthogonal transform coefficient; means for quantizing the orthogonal transform coefficients and calculating the quantized orthogonal transform coefficients; means for encoding the quantized orthogonal transform coefficients; performing inverse orthogonal transform on the quantized orthogonal transform coefficients;
A motion compensation frame comprising means for calculating a quantized prediction error, means for calculating a reproduced image based on the quantized prediction error and the prediction signal, means for accumulating the reproduced image, and means for encoding a motion vector. The above object is achieved by an intercoding device.

Function: A conventional motion compensated interframe coding device compares the input television signal with the reproduced television signal of the previous frame stored in the image memory, calculates the motion compensation vector of the encoded block, and calculates the motion compensation vector of the encoded block. The effectiveness of motion compensation is determined using the difference between the previous frame and the current frame, and the difference between the predicted pixel value using motion compensation and the pixel value of the current frame.

However, depending on these values, in areas where there are many blocks for which determination is made near the boundary of whether or not to perform motion compensation, there will be a mixture of blocks that will be motion compensated and blocks that will not be motion compensated. Particularly when the entire screen is translated in parallel, if there is a block that is not motion compensated and is surrounded by motion-compensated blocks in a flat part of the screen, this will cause deterioration in image quality.

Therefore, according to the present invention, when the motion vector of the encoded pro-sequence is the same as the motion vector of an adjacent neighboring block, the present invention corrects the determination and performs motion compensation even for a block that is determined not to be motion compensated. This improves image quality.

EXAMPLE A first example of the present invention will be described below with reference to FIG. FIG. 1 is a block diagram of a motion compensated interframe coding apparatus in a first embodiment of the present invention. In FIG. 1, 1 is an input terminal into which an input television signal is input, and 3 is an input terminal that compares the image signal of the encoded block of the current frame with the reproduced image signal of the previous frame, and calculates the motion vector of the encoded block and the first motion. A first motion compensation determination unit calculates a compensation control signal; 4 is an image memory unit that stores reproduced image signals of the current frame and the previous frame; 8 stores the first motion compensation control signal and motion vectors; It is determined whether or not to motion compensate the encoded block, and the result is sent to the second motion compensation control signal l2.
14 is a motion compensation unit that performs motion compensation for the reproduced image signal of the previous frame; 15 is a second motion compensation determination unit that outputs the output to
An in-loop filter section performs two-internal low-pass filter processing on the motion compensation control signal; l8 is a prediction error calculation section that calculates a prediction error by calculating the difference between the original signal and the predicted signal of the encoded block; and 20 is a prediction section. 22 is an orthogonal transform unit that orthogonally transforms the error signal; 22 is a quantizer that quantizes orthogonal transform coefficients; 25 is an inverse orthogonal transform unit that performs inverse orthogonal transform on the quantized orthogonal transform coefficients; and 27 calculates a reproduced image of the current frame. 29 is a prediction error encoding unit that encodes a prediction error through a channel, 3l is a motion vector encoder that encodes a motion vector through a channel, and 33 calculates a transmission frame from a prediction code and a motion vector code. The constituent multiplexer section 35 is a code memory section that temporarily stores transmission frames, and 37 is an output terminal that outputs a transmission signal.

The operation of the above configuration will be explained below.

The television signal is converted from analog to digital by a signal processing unit not shown in Fig. 1, and is converted into M pixels in the horizontal direction.
It is divided into blocks of N lines in the vertical direction, and is input as an input television signal 2 from an input terminal l. Next, the first
The motion compensation determination section 3 compares the input television signal 2 with the reproduced image 5 of the previous frame read out from the image memory section 4, and calculates a motion vector 6. At the same time, the first motion compensation determining unit 3 determines whether motion compensation for the processing block is valid or invalid using the evaluation value at the time of calculating the motion vector, and outputs the result as the first motion compensation control signal 7. The second motion compensation determining unit 8 determines the motion vector 6 of the encoded block and the first motion vector 6 of the encoded block.
The motion compensation control signal 7 is accumulated, a final judgment is made as to whether motion compensation is effective for the encoded block, and the result is output as a second motion compensation control signal 12. Furthermore, when the motion compensation for the encoded block is finally determined to be effective, the second motion compensation determination unit 8 outputs the motion vector for the accumulated encoded block as the second motion compensation control signal 12.

Therefore, the second motion compensation control signal 12 has a motion vector and a motion compensation signal superimposed thereon.

Below, a method for ultimately determining whether motion compensation is valid or invalid will be described.

(1) First motion compensation control signal 7 for encoded block
If it is ON, the second motion compensation control signal 12 is turned ON and the determination is completed.

(2) Motion vector (VX(i).V
Y(j)) and the motion vectors (Vx(I-t).VY(j-1
))． (Vx(;).Vy(j-1)). (
Vx(t+1). Vy(;-t)). (Vx(I-
t), Vy('')), (Vx(t+t), vY(
j)) ． (VX(i-1).Vy(++1))
．． (Vx(+).VY(j+1)).
(VX(i+1).VY(J+1)), the motion vectors of the reference blocks to be motion compensated are compared, the number of blocks whose motion vectors match is counted, and the number of matches is greater than or equal to a predetermined value K. In this case, the first motion compensation control signal 7 is corrected and the second motion compensation control signal 12 is on l,
, otherwise the second motion compensation control signal is turned off.

According to experiments, it has been confirmed that when K=4, the image quality is improved.

The motion compensation unit l4 performs motion compensation using the motion vector when motion vector information 12 is used to compensate for the reproduced image 15 of the encoded block, and when motion compensation is not performed, the motion compensation unit 14 performs motion compensation without asking.
It is output as a motion compensation signal 16. The in-loop filter unit 15 tfi performs in-loop filter processing on the motion compensation signal 16 and outputs it as a prediction signal l7.

This processing method requires the motion vectors of eight neighboring blocks for in-loop filter processing of the encoded block, so the start of processing of the encoded block is delayed by N lights compared to the conventional example, but the delay time is Processing frame rate; 1
0 FRAME/8EC, l frame total number of lines; 2
In the case of 88 lines and N=8, it is about 3 mSEC, and its influence can be almost ignored.

The prediction error calculation unit l8 performs a difference calculation between the input television signal 2 and the prediction signal 17 of the encoded block, and outputs the result as a prediction error signal l9. Orthogonal transformation unit 20
performs orthogonal transformation on the prediction error signal 19, removes the high correlation between neighboring pixels of the prediction error signal l9, and calculates the prediction error orthogonal transformation coefficient 21. As the orthogonal transform method, in many cases, discrete cosine transform is used, which has high transform efficiency and can be implemented in hardware. The quantizer 22 is a quantizer whose quantization characteristics change depending on the generated code amount 23, and the prediction error orthogonal transform coefficient 2
1 is quantized, and a prediction error orthogonal transform quantization coefficient 24 is calculated. The inverse orthogonal transform unit 25 performs inverse orthogonal transform on the prediction error orthogonal transform quantization coefficient 24 to calculate a prediction error signal 26 including the quantization error. The reproduced image calculation unit 27 adds the prediction error signal 26 including the quantization error and the prediction signal l7, and calculates the reproduced image 28 of the encoded block. The image memory 4 stores the reproduced image signal 28 of the current frame and outputs the reproduced image signals 5 and 15 of the previous frame. The prediction error encoding unit 29 encodes the prediction error orthogonal transform quantization coefficient 24 and calculates a prediction error code 30. Motion vector encoding unit 3
l encodes the motion vector l2 of the motion-compensated block, and calculates the motion vector code 32. Multiplexer section 3
3 calculates a transmission frame 34 in a predetermined format from the prediction error code 30 and the motion vector code 32. Code memory section 3
5 stores the transmission frame 34 once, and then converts it to the transmission code 3 in synchronization with a clock signal input from an external device (not shown).
6 from the output terminal 37.

As is clear from the above description, according to this embodiment, the second
The motion compensation determination unit 8 compares the motion vector of the encoded block with the motion vector of the adjacent peripheral block, and if the motion vector of the encoded block is the same as the motion vector of the adjacent peripheral block, it determines that no motion compensation is required. By performing motion compensation on the determined blocks, it prevents deterioration in image quality caused by a mixture of motion-compensated blocks and non-motion-compensated blocks in flat areas of the screen when the entire screen is translated. , with improved image quality.

In addition, in the above explanation, for a block that is determined not to be motion compensated, the determination is corrected and whether or not motion compensation is to be performed is determined based on the motion vector of the encoded block and the surrounding blocks to be motion compensated adjacent to the encoded block. We have shown an example where the judgment is made based on the number of matching motion vectors, but the number that can be considered a match is
It may be determined by

In addition, in the above explanation, an example was shown in which a motion vector is detected using the reproduced image of the previous frame and the current image of the current frame, but it is also possible to detect a motion vector using the original image of the previous frame and the original image of the current frame , a motion vector may be detected.

Effects of the Invention As described above, the effects of the present invention include, regarding the determination of the effectiveness of motion compensation, for an encoded block determined not to be motion compensated, the motion vector of the encoded block and the motion vector of the adjacent peripheral block are means for temporarily storing the coded block, and a motion vector of the coded block is compared with the motion vector of an adjacent peripheral block, and if the motion vector of the coded block is the same as the motion vector of the adjacent peripheral block, it is determined that motion compensation is not performed. By providing a means for motion compensation, it is possible to prevent deterioration in image quality caused by a mixture of motion compensated blocks and non-motion compensated blocks in flat areas on the screen, such as when the entire screen is translated in parallel. By preventing this, image quality can be improved, and the effect is significant.

[Brief explanation of drawings]

FIG. 1 is a block diagram of a motion-compensated interframe coding device according to an embodiment of the present invention, FIG. 2 is a diagram showing the positional relationship between a coding block and adjacent peripheral blocks, and FIG. 3 is a diagram showing a conventional motion compensation interframe coding device. FIG. 2 is a block diagram of a compensated interframe coding device. 1, 4l... Input terminal, 3... First motion compensation determining unit, 43... Motion vector calculating unit, 8... Second motion compensation determining unit, 4, 44... Image memory unit, 14, 48...
- Motion compensation section, 15, 50... Loop filter section,
18, 52... Prediction error calculation unit, 20, 54...
Orthogonal transformation unit, 22, 56...Quantization unit, 25, 59...
- Inverse orthogonal transformation section, 27, 6l... Reproduction image calculation section, 2
9, 63... Prediction error encoding unit, 31, 65... Motion vector encoding unit, 33, 67... Multiplexer unit,
35, 69... code memory section, 37, 7l... output terminal.

Claims (1)

[Claims] means for converting a television signal from analog to digital; means for dividing a frame or field of a digitized input television signal into blocks of a defined size; means for calculating a vector; and first motion compensation determining means for determining whether or not to perform motion compensation for a coded block based on the interframe difference value, and calculating the result as a motion compensation control signal; means for accumulating motion vectors and motion compensation control signals of the encoded block and surrounding blocks adjacent to the encoded block;
The number of blocks whose motion vectors can be considered to match by comparing the motion vector of the encoded block determined not to undergo motion compensation by the first motion compensation determination means and the motion vector of surrounding blocks adjacent to the encoded block. is K (however,
(K is a positive integer of 8 or less) or more, a motion compensation control signal correction means for changing the motion compensation control signal to perform motion compensation; and a pixel value of the encoded block and the corrected motion compensation control signal. A means for calculating a difference from a predicted pixel value based on a signal as a prediction error value, a means for orthogonally transforming the predicted error value and calculating an orthogonal transform coefficient, and a means for quantizing the orthogonal transform coefficient and orthogonal transform that is quantized. means for calculating coefficients, means for encoding quantized orthogonal transform coefficients, means for performing inverse orthogonal transform on quantized orthogonal transform coefficients and calculating quantized prediction errors, and quantized prediction errors and predictions. A motion compensated interframe encoding device comprising means for calculating a reproduced image from a signal, means for accumulating the reproduced image, and means for encoding a motion vector.