JPH0748860B2 - Video coding device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a moving picture coding device used for a videophone, a video conference and the like.

2. Description of the Related Art Generally, this type of moving picture coding apparatus uses a motion-compensated image, and this motion-compensated image has a pixel block whose pixel value is closest to an arbitrary pixel block of the current image from the previous image. Is an image obtained by performing the above operation on all pixel blocks of the current image by considering the movement between the images, and is an image having a pixel value close to that of the current image.

FIG. 3 shows the configuration of a general moving picture coding apparatus.

In FIG. 3, reference numeral 31 is a frame memory for storing images of the current frames of two consecutive frames (current image), and 32.
Is a differencer that calculates a prediction error that is the difference between the current image from the frame memory 31 and the motion-compensated image from the motion compensator 39, and 33 converts the prediction error calculated by the differencer 32 into the frequency domain. Prediction error converter, 34 is a quantizer that quantizes the frequency domain converted by the prediction error converter for each frequency component, 40 is the frequency domain quantized by the quantizer 34, the receiving side Is an encoder for transmitting to.

Further, 35 is an inverse quantizer which inversely quantizes the frequency domain quantized by the quantizer 34, and 36 is a prediction error which converts the frequency domain inversely quantized by the inverse quantizer 35 into a prediction error. The inverse converter 37 is an adder for adding the prediction error converted by the prediction error inverse converter 36 and the motion-compensated image from the motion compensator 39 to reproduce the previous image, and writing it in the frame memory 38. .

FIG. 4 shows the configuration of a conventional motion compensator 39 in the above moving picture coding device.

In FIG. 4, 41a is a small area divider that divides the current image from the frame memory 31 into small areas (pixel blocks) of M pixels × N lines, and outputs each small area, and 41b is a small area divider from the frame memory 38. 42 is a small area divider 42 which divides the previous image into small areas of M pixels × N lines and outputs each small area, as shown in the upper part of FIG.
A motion vector that calculates the difference value of the pixel values of the current image and the previous image for each of the divided small regions, and calculates the motion vector between the current image and the previous image by the sum of the pixel value differences in each small region. The calculator 43 is a motion-compensated image generator that generates a motion-compensated image of the current image based on the previous image and the motion vector calculated by the motion vector calculator 42.

Therefore, according to the above conventional example, the small area dividers 41a, 4a
For each small area divided by 1b, the difference value of the pixel values of the current image and the previous image is calculated, and the motion vector between the current image and the previous image is calculated by the sum of the pixel value differences in each small area. , The motion compensation image of the current image can be generated by this motion vector and the previous image.

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention However, in the motion compensator in the above-described conventional moving picture coding device, the moving vector calculator 42 calculates the difference value of the pixel values of the current image and the previous image for each small area, and each small area is calculated. The current image and the motion vector between the previous images are evaluated by the sum of the differences in the pixel values in the region, so the prediction error, which is the difference between the current image and the motion-compensated image, is converted into the frequency domain and quantized, Even if the coding is performed, the generated code amount is not always the minimum.

Further, in the above-mentioned conventional example, since all pixels are targets of the difference calculation, there is a problem that the calculation time becomes long.

The present invention solves the above-mentioned conventional problems, and an object of the present invention is to provide a moving picture coding apparatus capable of minimizing the code amount of a prediction error and shortening the calculation time. .

Means for Solving the Problems In order to achieve the above object, the present invention transforms pixel values of images of two frames into frequency regions for each small region, and uses the frequency components as conversion coefficients, and The difference between the conversion coefficients is calculated for each small area, and the position where the sum is the smallest is detected as a motion vector between images.

Effect of the Invention With the above-described configuration, the present invention can minimize the code amount of the prediction error when the prediction error is detected from the motion vector and the current image, and also extracts the predetermined frequency component as the conversion coefficient to perform the calculation. The time can be reduced.

Embodiments Embodiments of the present invention will be described below with reference to the drawings. First
FIG. 1 is a block diagram showing an embodiment of a motion compensator of a moving picture coding apparatus according to the present invention, and FIG. 2 is an operation explanatory view of the moving picture coding apparatus of FIG.

In FIG. 1, 11a is a small area divider which divides the current image from the frame memory 31 as shown in FIG. 3 into small areas (pixel blocks) of M pixels × N lines, and outputs each small area. Reference numeral 11b is a small area divider that divides the previous image from the frame memory 38 as shown in FIG. 3 into small areas of M pixels × N lines, and outputs each small area, and 12a and 12b are small area divisions, respectively. This is a converter that converts the pixel values of the current image and the previous image into the frequency domain for each of the small regions divided by the devices 11a and 11b, and extracts the frequency components as conversion coefficients.

13, the current image, respectively extracted by the converter 12a, 12b, calculates the difference value of the conversion coefficient of the frequency component of the previous image,
A motion vector calculator that calculates the position with the smallest total sum as a motion vector, and 14 is a previous image and a motion vector calculator 13
It is a motion compensation image generator that generates a motion compensation image of the current image by the motion vector calculated by and outputs it to the differentiator 32 as shown in FIG.

Next, the operation of the above embodiment will be described with reference to FIGS.

When the pixel values of the current image and the previous image are converted into the frequency domain by the small area dividers 11a and 11b for each of the small areas of M pixels × N lines, and are converted into the conversion coefficient of the frequency component, the second As shown in the lower part of the figure, the low frequency component corresponds to the upper left component and the high frequency component corresponds to the lower right component, and the value thereof is smaller than that of the conventional example, which is not shown in the upper part of FIG.

Therefore, the motion vector calculator 13 calculates the difference value of the conversion coefficients of the frequency components of the current image and the previous image, calculates the position with the smallest sum as the motion vector, and the motion compensation image generator 14 When the motion compensation image of the current image is generated by the motion vector and the differencer 32 calculates the prediction error which is the difference between the current image and the motion compensation image, the code amount of the prediction error can be reduced.

In addition, the frequency component required to calculate the motion vector,
For example, the calculation time can be reduced by using only the conversion coefficient of the low frequency component as shown in the lower part of FIG. 2 for the difference calculation.

EFFECTS OF THE INVENTION As described above, according to the present invention, the pixel values of the images of two frames are converted into the frequency domain for each small area, and the frequency component is used as the conversion coefficient, and the difference between the conversion coefficients of the pixels is calculated. Since it is calculated for each small area and the position where the sum is the smallest is detected as a motion vector between images,
When the prediction error is detected from the motion vector and the current image, the code amount of the prediction error can be minimized, and the extraction of a predetermined frequency component as the conversion coefficient can reduce the calculation time.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of a motion compensator of a moving picture coding apparatus according to the present invention, FIG. 2 is an operation explanatory view of the moving picture coding apparatus of FIG. 1, and FIG. FIG. 4 is a block diagram showing a general moving picture coding device, and FIG. 4 is a block diagram showing a conventional motion compensator. 11a, 11b …… Small area divider, 12a, 12b …… Converter, 13 ……
Motion vector calculator, 14 ... Motion compensation image generator, 32 ...
Difference unit, 33 ... Prediction error converter, 34 ... Quantizer, 40 ...
… Encoder.

Claims (3)

[Claims] 1. A means for dividing an image of two continuous frames into small regions, and pixel values of the images of the two frames are transformed into frequency regions for each of the small regions, and the frequency components thereof are transformed into transform coefficients. And a means for calculating the difference between the conversion coefficients of the respective images for each small area and detecting a position where the sum is the smallest as a motion vector between the images, and motion compensation by the motion vector and the previous image. A unit for generating an image, a unit for calculating a prediction error from the motion compensation image and the current image, a unit for converting the prediction error into a frequency domain, and a unit for quantizing and coding the frequency domain for each frequency component. And a video encoding device having. 2. A pixel value of an image of each of two frames is converted into a frequency domain for each small area, and a predetermined frequency component is extracted as a conversion coefficient.
The moving picture encoding device described. 3. The moving picture coding apparatus according to claim 2, wherein the predetermined frequency component is a low frequency component.