VIDEO CODING APPARATUS

Abstract

A video coding apparatus carries out a compression coding of a video based on a result of predicting a motion vector predicted between frames of the video. A quantization parameter control unit comprised of the apparatus calculates a ratio of an accumulation value, in the small block, of a prediction error of a brightness component to an accumulation value, in the small block, of a prediction error of a color difference component at the time that a motion vector detection/compensation unit which carries out a motion compensation based on a prediction result of the motion vector for the small block designated in a frame of the above video as a prediction accuracy indicator of the foregoing motion vector, and carries out a control of a quantization unit executing a quantization of image information of the small block based on the prediction accuracy indicator.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be more apparent from the following detailed description when the accompanying drawings are referenced.

FIG. 1 is a diagram describing problems of a conventional technique;

FIG. 2 is a diagram showing a configuration of a coding apparatus embodying the present invention;

FIG. 3 is a diagram showing a flow chart of details of a control process carried out by a quantization parameter control unit; and

FIG. 4 is a diagram exemplifying a configuration of a computer embodying the present invention.

Claims

1. A video coding apparatus carrying out compression coding of a video based on a prediction result of a motion vector predicted between frames of the aforementioned video which is expressed by a brightness component and a color difference component, including: a brightness component prediction error calculation unit for calculating a prediction error of a brightness component by a motion compensation prediction based on the prediction result of the motion vector for a small block designated in the frame of the video;a color difference component prediction error calculation unit for calculating a prediction error of a color difference component by the motion compensation prediction;a quantization method determination unit for determining a most optimal quantization method from among a plurality thereof, based on inputs of the prediction error of the brightness component which is calculated by the brightness component prediction error calculation unit and of the prediction error of the color difference component which is calculated by the color difference component prediction error calculation unit; anda quantization unit for quantizing image data by the quantization method determined by the quantization method determination unit.

2. The video coding apparatus according to claim 1, wherein said quantization method determination unit indicates a degradation of a prediction accuracy of said motion vector as a prediction accuracy indicator when an accumulation value of a prediction error of said color difference components within a small block becomes larger than an accumulation value of a prediction error of said brightness components within the small block.

3. The video coding apparatus according to claim 2, wherein said quantization method determination unit indicates a degradation of a prediction accuracy of said motion vector as a prediction accuracy indicator when a ratio of the accumulation value of a prediction error of said color difference component within the small block to the accumulation value of a prediction error of said brightness component within the small block becomes larger than a predefined threshold value.

4. The video coding apparatus according to claim 1, wherein said quantization method determination unit controls a quantization parameter in a quantization at said quantization unit.

5. The video coding apparatus according to claim 4, wherein said quantization method determination unit makes said quantization parameter smaller when judging that a prediction accuracy of said motion vector is degraded.

6. The video coding apparatus according to claim 5, wherein said quantization method determination unit further controls said quantization unit based on an information volume of a video which has been compression-coded, thereby changing an information volume of a brightness component in image information after the quantization.

7. The video coding apparatus according to claim 6, wherein said quantization method determination unit carries out a control for reducing the information volume of a brightness component in image information after said quantization for said quantization unit, thereby limiting the information volume of said compression-coded video within a predetermined threshold value.

8. The video coding apparatus according to claim 7, wherein said control applied by said quantization method determination unit is one for reducing, to zero (“0”), a coefficient value whose absolute value is smaller than a predefined value among the aforementioned coefficient values of a brightness component in said post-quantization image information.

9. The video coding apparatus according to claim 7, wherein said control applied by said quantization method determination unit is one for widening a dead zone width for said quantization.

10. A computer readable recording medium recording a program and allowing a computer to read the recorded program for making the computer carry out a compression coding of a video based on a result of a prediction of a motion vector which is predicted between frames of the aforementioned video expressed by a brightness component and a color difference component, wherein the aforementioned program makes the computer carry out the processes for:calculating a prediction error of a brightness component by a motion compensation prediction based on the prediction result of the motion vector for a small block designated in the frame of the video;calculating a prediction error of a color difference component by carrying out the motion compensation prediction;determining a most optimal quantization method from the prediction error of the brightness component and that of the color difference component; andquantizing image data by the determined quantization method.

11. The recording medium according to claim 10, wherein said process for determining the quantization method indicates a degradation of a prediction accuracy of said motion vector as a prediction accuracy indicator when an accumulation value of a prediction error of said color difference component within a small block becomes larger than an accumulation value of a prediction error of said brightness component within the small block.

12. The recording medium according to claim 11, wherein said process for determining the quantization method indicates a degradation of a prediction accuracy of said motion vector as a prediction accuracy indicator when a ratio of the accumulation value of a prediction error of said color difference component within the small block to the accumulation value of a prediction error of said brightness component within the small block becomes larger than a predefined threshold value.

13. The recording medium according to claim 10, wherein a quantization parameter for said quantization process is controlled by said process for determining a quantization method.

14. The recording medium according to claim 13, wherein said quantization parameter for said quantization process is made smaller if a prediction accuracy of said motion vector is determined to be degraded in said process for determining a quantization method.

15. The recording medium according to claim 14, wherein said control for a quantization by said process for determining a quantization method further changes an information volume of a brightness component in image information after the aforementioned quantization based on an information volume of a compression-coded video.

16. The recording medium according to claim 15, wherein said control for a quantization by said process for determining a quantization method applies a control for reducing the information volume of a brightness component in image information after the aforementioned quantization, thereby limiting the information volume of said compression-coded video within a predetermined threshold value.

17. The recording medium according to claim 16, wherein said control for a quantization by said process for determining the quantization method is one for reducing, to zero (“0”), a coefficient value whose absolute value is smaller than a predefined value among the aforementioned coefficient values of a brightness component in image information after the aforementioned quantization.

18. The recording medium according to claim 16, wherein said control for a quantization by said process for determining a quantization method is one for widening a dead zone width for the aforementioned quantization.

19. A method for carrying out a compression coding of a video based on a result of predicting a motion vector which is predicted between frames of the aforementioned video expressed by a brightness component and a color difference component, including: calculating a ratio of an accumulation value, in a small block, of a prediction error of a brightness component at the time of carrying out a motion compensation based on the prediction result of the motion vector for the aforementioned small block designated in a frame of the video to an accumulation value, in a small block, of a prediction error of a color difference component at the time of carrying out the aforementioned motion compensation, as a prediction accuracy indicator of the aforementioned motion vector; andcontrolling a quantization of image information of the small block based on the prediction accuracy indicator.

20. The method according to claim 19, wherein said control of said quantization further controls said quantization based on an information volume of a video which has been compression-coded, thereby changing an information volume of a brightness component in image information after the quantization.