JPH022357B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Technical Field of the Invention The present invention relates to an image signal band compression processing device,
In particular, the present invention relates to an adaptive coding system that can obtain a high compression ratio by adaptively switching the coding rule for motion-compensated blocks.

Prior Art and Problems The motion compensation coding method subdivides one frame of the screen into arbitrary blocks, and generates a motion vector indicating the amount and direction of inter-frame motion for each block, and an arbitrary block from the corresponding block in the previous frame. The image signal is transmitted based on the error (prediction error) between the predicted value of the block in the current frame and the predicted value based on the prediction function of the block.

Conventionally, in inter-frame coding in such motion compensation coding methods, it has been difficult to directly encode and transmit motion-compensated prediction errors, or to perform fixed intra-frame prediction and transmit quantized output. It was based on one of the following methods. However, these two methods have advantages and disadvantages; depending on the degree of movement on the screen, the former method may provide a better compression ratio, while the latter method may provide a better compression ratio. Therefore, no matter which method is adopted, good results cannot be obtained in all cases.

Purpose of the Invention The present invention aims to solve the problems of the prior art as described above, and its purpose is to provide coding that directly codes and transmits motion-compensated prediction errors, and fixed intra-frame prediction. An object of the present invention is to provide an encoding method that can obtain a high compression rate by adaptively switching between encoding and transmitting quantized output depending on the input signal.

Structure of the Invention The adaptive coding method of the present invention calculates the sum of absolute values of prediction errors for each block, and calculates the difference between the prediction error of the current pixel and the prediction error of a pixel shifted by one pixel in the scanning direction. The sum of absolute values is calculated, and the encoding method is switched based on the result of comparing the magnitudes of the two.

Embodiment of the Invention FIG. 1 shows the configuration of an embodiment of the adaptive encoding system of the present invention. In the figure, 1 is a motion vector detection unit, 2 is a frame memory, 3 is a variable delay unit, 4 is a subtracter, 5 is a determination circuit, 6 is a selector, 7 is a delay circuit (D), 8 is a subtracter, 9 is a quantizer
(Q), 10 is an adder, 11 is a delay circuit (D), and 12 is an adder.

In FIG. 1, an input image signal is applied to a motion vector detection section 1, and compared with the image signal of the previous frame stored in a frame memory 2.
Generates a motion vector Vopt indicating the amount and direction of motion. The variable delay unit 3 changes its delay amount by adding the motion vector Vopt detected by the motion vector detection unit 1, and changes the amount of delay by adding the motion vector Vopt detected by the motion vector detection unit 1.
The predicted value signal is generated by delaying the image signal of the previous frame stored in the image signal. The subtracter 4 subtracts the predicted value signal from the input image signal for each pixel to generate a difference signal. This difference signal is applied to the determination circuit 5, where it is determined which encoding should be performed for each block, as will be described later.
As determination information from the determination circuit 5, "1" is generated when the amount of information is larger if the direct encoding is performed, and "0" is generated when the amount of information is larger if the encoding is performed by fixedly performing intra-frame prediction. occurs. This determination information is applied to the selector 6, and the selector 6 selects a predicted signal based on this information.

On the other hand, the difference signal from the subtracter 4 is applied to the delay circuit 7, and is delayed by the time until the determination operation in the determination circuit 5 is completed. This requires that the selector 6 completes switching before the next subtraction in the subtracter 8 is performed, but the determination in the determination circuit 5 is 1.
This is because the input to the subtracter 8 must be waited for since it is performed in units of blocks. The output of the delay circuit 7 is applied to a subtracter 8, and the predicted value signal from the selector 6 is subtracted therefrom to generate a difference signal. This difference signal is applied to a quantizer 9 and quantized to generate quantized error information.

Further, this quantized error information signal is added to the signal from the selector 6 in an adder 10. When the determination information is "1" and the output of the delay circuit 11 is selected by the selector 6, the decoded signal output from the delay circuit 11 for one pixel before is output as a signal of the predicted value in the frame, and the determination information When is "0", a no-signal state is selected and output as a predicted value signal. As a result, when the determination information is "1", the subtracter 8 subtracts the predicted value signal in the frame from the delayed difference value signal of the delay circuit 7 to obtain the difference value signal. This signal is quantized by a quantizer 9 to generate quantized error information. On the other hand, when the determination information is "0", the predicted value is not input to the subtracter 8,
The quantizer 9 directly quantizes the delayed difference value signal of the delay circuit 7 to generate quantized error information.

FIG. 2 shows an example of the configuration of the determination circuit in FIG. 1. In the figure, 21 is an absolute value circuit;
2 is an adder, 23 is a flip-flop (FF), 2
4 is a gate, 25 is a subtracter, 26 is a one-pixel delay circuit (D), 27 is an absolute value circuit, 28 is an adder, 29
is a flip-flop (FF), 30 is a gate, 31
is a comparator.

In FIG. 2, the absolute value of the difference value signal from the subtracter 4 shown in FIG. 1 is determined in an absolute value circuit 21. In FIG. The output of the absolute value circuit 21 is added to the cumulative value signal from the flip-flop 23 in the adder 22, so that the flip-flop 23 generates an output in which the absolute value of the difference value is accumulated within one block. At this time, the gate 24 is closed by the reset signal when the first difference value of one block is output from 21, and the flip-flop 23 is cleared for each block. The difference value signal is also applied to a subtracter 25, where the difference value of the previous pixel is subtracted, thereby generating a signal of a composite difference value (difference value of difference values) when prediction is made from the pixel of the previous pixel. . The absolute value of this signal is determined in an absolute value circuit 27. The output of the absolute value circuit 27 is added to the cumulative value signal from the flip-flop 29 in an adder 28, so that the flip-flop 29 generates an output that is accumulated within one block. At this time, the gate 30 is set to 1 by the reset signal.
When the first composite absolute difference value of the block is output from 27, it is closed and the flip-flop 29
Clear each block. The comparator 31 compares the accumulated values of both flip-flops 23 and 29, and when the output of the flip-flop 23 is large, it outputs "1" as determination information, and the output of the flip-flop 29 is
When the output is large, "0" is output as determination information.

In this way, the adaptive coding method shown in FIG. A predicted value for each pixel is obtained with a variable delay, the difference between this predicted value and the current image signal is obtained, and the absolute value of the difference value is accumulated for each block, and the signal is the sum of the absolute values of the error information, and 1
By comparing the difference value predicted from the previous pixel difference value and the absolute value of the difference between the difference value of the current pixel and the composite difference absolute value signal accumulated for each block, the difference value within the frame is determined. Determine whether or not to perform prediction (predicted value of difference value).

Next, after delaying the difference value signal by a time corresponding to the determination operation time of the determination circuit, when it is determined that intra-frame prediction is to be performed, the difference between this difference value and the predicted difference value is calculated. is quantized to generate error information. When it is determined not to perform intra-frame prediction, the difference value is directly quantized without subtracting the difference predicted value, and quantized error information is obtained. As described above, in the adaptive encoding method of the present invention, since the encoding method is switched depending on the input information, a high compression ratio can be obtained regardless of the state of the input signal.

Effects of the Invention As explained above, according to the adaptive coding method of the present invention, a signal (absolute value sum ) and the cumulative value (composite difference absolute value sum) obtained by accumulating the absolute value of the amount of change for each adjacent pixel in the difference value, the frame is determined based on the difference value. Since the difference value between the predicted value predicted within and the difference value is quantized and encoded, or the difference value is directly quantized and encoded, the high compression ratio can be obtained.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the configuration of an embodiment of the adaptive encoding method of the present invention, and FIG. 2 is a diagram showing an example of the configuration of a determination circuit. 1... Motion vector detection unit, 2... Frame memory, 3... Variable delay unit, 4... Subtractor, 5...
Judgment circuit, 6...Selector, 7...Delay circuit (D),
8...Subtractor, 9...Quantizer (Q), 10...
Adder, 11...delay circuit (D), 12...adder,
21... Absolute value circuit, 22... Adder, 23...
Flip-flop, 24...Gate, 25...Subtractor, 26...1-pixel delay circuit, 27...Absolute value circuit, 28...Adder, 29...Flip-flop, 30...Gate, 31...Comparator .

Claims (1)

[Scope of Claims] 1. Motion vector information obtained by dividing image information into blocks and comparing image information of corresponding blocks frame by frame, and a block of the current frame and the previous frame according to the motion vector. In a motion compensation coding method, an image signal is encoded based on information on a predicted value predicted from a corresponding block of a frame, and error information. and the signal of the sum of absolute values of the difference between the processed signal and the unprocessed signal in the difference value between the input image signal and the motion-compensated predicted value signal for each block. Depending on the motion compensation, the difference value signal of the block that has been motion compensated is directly quantized to generate error information, or the difference value signal that has been fixedly subjected to intra-frame prediction is quantized and error information is generated. An adaptive encoding method characterized by switching.