JPH0556416A - In-loop filter control system for inter-frame predictive coding device - Google Patents

Abstract

PURPOSE:To efficiently and effectively execute the ON/OFF control of an in- loop filter in the hybrid coding system of the combination of inter-frame predictive coding and orthogonal transform coding. CONSTITUTION:A control signal to calculate each absolute value sum of inter- frame predicted error signals when the in-loop filter 4 is turned on and when it is turned off for every predetermined block unit, and to select the predicted error signal of the smaller absolute value sum by a comparator 11 is generated, and this predicted error signal of the smaller absolute value sum is encoded and transmitted as the inter-frame predicted error signal.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a television signal compression coding apparatus, and more particularly to a control method of an in-loop filter of an interframe predictive coding apparatus.

[0002]

2. Description of the Related Art As a compression coding technique for transmitting a moving picture television signal through a low-speed transmission path, a portion (prediction error) that is moved by interframe predictive coding (also interframe predictive coding with motion compensation). Techniques for transmitting only signals) are known. Furthermore, in order to compress information, a hybrid coding technique in which a prediction error signal generated by inter-frame prediction coding is subjected to orthogonal transform coding such as cosine transform, and only the component with high power is coded and transmitted as a significant component. Is known to realize a large amount of information compression of moving picture television signals.

However, the high-frequency component converted by the orthogonal transformation generally has low power and may not be transmitted. Therefore, when inter-frame predictive coding is used, high frequency components remain in the predictive coding loop and are output as noise to the decoded signal.

In order to solve the above problem, in the conventional compression coding apparatus, a band limiting filter (a filter for spatially cutting high frequency components: a prediction coding loop for an interframe prediction value is used as a loop). (It is called an inner filter) and used a filter in the loop for the part that moved. Further, the motion vector detected at the time of motion-compensated interframe predictive coding has been used to detect the moving part.

[0005]

The conventional compression coding apparatus described above needs to detect a moving portion for on / off control of the in-loop filter. Therefore, a motion detection circuit is needed. Further, depending on the error of motion detection and the characteristics of the in-loop filter, noise may not be completely removed and may remain in the loop.

The present invention has been made in view of the above-mentioned conventional circumstances, and therefore, an object of the present invention is to provide a novel interframe predictive coding apparatus capable of solving the above problems inherent in the conventional art. To provide a simple in-loop filter control method.

[0007]

In order to achieve the above object, an intra-loop filter control system of an interframe predictive coding apparatus according to the present invention is a prediction error signal obtained by interframe predictive coding of a television signal. Is a device for orthogonally transform-encoding, and quantizes the transformed components for transmission, and a predetermined first interframe prediction value and the first interframe prediction value.
And a second inter-frame prediction value that has been subjected to a predetermined spatial filter (in-loop filter) processing using a predetermined block (N lines × M pixels; N and M are positive integers) as a unit. In the inter-frame predictive coding apparatus for obtaining the prediction error signal by using one of the first and second inter-frame predicted values as the inter-frame predicted value in the block unit, Of the sum of absolute values of the first prediction error signal obtained by the inter-frame prediction value and the sum of absolute values of the second prediction error signals obtained by the second inter-frame prediction values of It comprises a means for encoding and transmitting the smaller prediction error signal and transmitting a signal for determining which of the prediction error signals is encoded and transmitted for each block. .

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described in detail with reference to the accompanying drawings with reference to the accompanying drawings.

FIG. 1 is a block diagram showing an embodiment of the present invention.

In FIG. 1, a PCM television signal is input to the input terminal 22 and connected to the subtracter 1 and the subtractor 2. In the subtractor 1 and the subtractor 2, the inter-frame prediction error is calculated, the output of the subtractor 1 is connected to the delay circuit 5 and the arithmetic unit 6, and the output of the subtractor 2 is connected to the delay circuit 8 and the arithmetic unit 7. To be done. In the arithmetic unit 6 and the arithmetic unit 7,
For each predetermined block, the sum of absolute differences of the prediction error signals of each block is calculated, and the comparator 11
Is output to. The delay circuit 5 and the delay circuit 8 are composed of an arithmetic unit 6
And a delay circuit for compensating the calculation delay time in the calculator 7. The prediction error signal delayed by the delay circuit 5 and the delay circuit 8 is connected to the selector 12.

The comparator 11 compares the difference absolute value sums of the prediction error signals for each block, and selects the control signal for selecting the prediction error signal having the small difference absolute value sum as the selector 12, the selector 13, and the delay. It outputs to each circuit 16. Selector 1
In 2, the prediction error signal having the smaller sum of absolute differences of the prediction error signals is selected based on the control signal from the comparator 11 and output to the orthogonal transform circuit 14. The prediction error signal from the selector 12 is orthogonally transformed in the orthogonal transformation circuit 14, and the transformed component is connected to the quantization circuit 15 and quantized by the quantization circuit 15, and the multiplexing circuit 21 and the dequantization circuit 19 are connected. Is output to. The multiplexing circuit 21 multiplexes the signal from the quantization circuit 15, the prediction error signal selection control signal delay-compensated by the delay circuit 16, and various control signals for compression coding, and outputs the multiplexed signal as a coded signal. Output to the terminal 23. The multiplexing circuit 21 also multiplexes a motion vector signal when it has a motion compensation function as a function of a compression coding unit.

The inverse quantization circuit 19 inversely transforms the quantized signal, outputs it to the inverse orthogonal transformation circuit 20, is inversely transformed in the inverse orthogonal transformation circuit 20, and is supplied to the adder 3 as a prediction error signal.

The adder 3 adds a prediction error signal to the interframe prediction value from the delay circuit 17 to obtain a locally decoded signal.
The locally decoded signal obtained by the adder 3 is input to the prediction value generation circuit 18 and used as a signal for generating the prediction value of the next frame. The predictive value generation circuit 18 generates a predictive value based on a motion vector signal in the case of simple inter-frame predictive coding, and in the case of having a motion compensation function, respectively. It outputs to the in-loop filter 4 and the delay circuit 24. In-loop filter 4
Then, predetermined filter processing is performed and the predicted value is supplied to the subtracter 1 and the delay circuit 9. Similarly, the second predicted value in which the delay in the in-loop filter 4 has been compensated for in the delay circuit 24 is the subtractor 2 and the delay circuit 1.
Connected to 0. The two prediction values are compensated for the delay time until the prediction error signal selection control signal is generated by the delay circuit 9 and the delay circuit 10, and the selector 13 selects the prediction value corresponding to the selected prediction error signal. It The delay of the predicted value selected by the selector 13 is compensated for by the delay circuit 17, and the predicted value is supplied to the adder 3.

The prediction error signal obtained by the predictive coding is orthogonally transformed by the orthogonal transformation circuit 14. An example that is often used in orthogonal transform coding of image signals is dis.
There is a create cosine transform coding (DCT). The DCT converts an image signal on the time axis into a signal on the frequency axis, divides a prediction error signal into predetermined blocks of N lines × M pixels, and a numerical sequence is a cosine function for each block. Is used for orthogonal transformation. The size of the block is generally set to about 8 lines × 8 pixels in consideration of the amount of calculation. In the image signal, the power is concentrated on the low-frequency component of the cosine-transformed components, and the power of the high-frequency component is generally small. By quantizing by the quantizer 15, the component of low power is eliminated and the generated information amount is suppressed. be able to.

The multiplexing circuit 21 variable length codes the quantized components by Huffman code, run length code or the like to form a frame for transmission, and also multiplexes selection signals and various control signals. ..

The in-loop filter 4 is a filter for removing noise by passing a signal distorted by quantization through a band limiting filter. Generally, a high-frequency component of low power has a lot of noise and is visually recognized. A low-pass filter that removes high-frequency components is used because it tends to have an adverse effect. In addition, the orthogonal transformation requires 2 in order to perform high efficiency encoding.
A spatial (two-dimensional) filter is generally used for the filter because the dimensional orthogonal transformation is performed.

The on / off control of the in-loop filter is determined by the comparator 11. The unit of the on / off control is generally orthogonal in consideration of the efficiency of transmitting the selection signal, the frame for transmission, and the like. There is a one-to-one correspondence with the conversion block or motion vector detection block.

[0018]

As described above, according to the present invention,
A band-limiting filter (in-loop filter) is provided for the inter-frame prediction value, and the in-loop filter is turned “on” and “off” in predetermined block units.
In this case, by comparing the sum of absolute differences of the prediction error signals and controlling the on-off filter in the loop, efficient coding can be performed, and in the inter-frame prediction coding loop by the quantization of orthogonal transform coding. It is possible to effectively remove the noise generated in the loop and to control the band limiting filter in the loop without providing a motion detection circuit as in the conventional case.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

[Explanation of symbols]

 1, 2 ... Subtractor 3 ... Adder 4 ... In-loop filter 5, 8, 9, 10, 16, 17, 24 ... Delay circuit 6, 7 ... Arithmetic unit 11 ... Comparator 12, 13 Selector 14 ... Orthogonal transform Circuit 15 ... Quantization circuit 18 ... Prediction value generation circuit 19 ... Inverse quantization circuit 20 ... Inverse orthogonal transformation circuit 21 ... Multiplexing circuit 22 ... Input terminal 23 ... Output terminal

Claims (1)

[Claims] 1. A device for orthogonally transform-encoding a prediction error signal obtained by performing interframe predictive coding of a television signal, quantizing the transformed component, and transmitting the component, wherein a predetermined first interframe is provided. The predicted value and a block in which the first inter-frame predicted value is predetermined (N lines x
M pixels; N and M are positive integers), and a predetermined spatially filtered second interframe prediction value, and the first and second interframe prediction values in block units. In the interframe predictive coding apparatus that obtains the prediction error signal by using any one of the following, the sum of absolute values of the first prediction error signal obtained from the first interframe prediction value for each block: , Comparing the sum of absolute values of the second prediction error signals obtained by the second inter-frame prediction value, and as a result of the comparison, the prediction error signal having the smaller sum of absolute values is encoded and transmitted,
An intra-loop filter control method for an interframe predictive coding apparatus, which transmits a signal for determining which of the prediction error signals has been coded and transmitted for each block.