Color motion artifact detection and processing apparatus compatible with video coding standards

#The present invention relates to processing of video data, and more specifically to detection and reduction of color-motion artifacts in processing of video data.

#Successive frames in a typical video sequence are often very similar to each other. For example, a sequence of frames may have scenes in which an object moves across a stationary background, or a background moves behind a stationary object. Consequently, many scenes in one frame may also appear in a different position of a subsequent frame. Video systems take advantage of such redundancy within the frames by using predictive coding techniques, such as motion estimation and motion compensation, to reduce the volume of data required in compressing the frames.

#In accordance with the well-known motion estimation technique, to conserve bit rate, data related to the differences between positions of similar objects in successive frames are captured by one or more motion vectors. The motion vectors are then used to identify the spatial coordinates of the shifted objects in a subsequent frame. The motion vectors therefore limit the bit rate that would otherwise be required to encode the data associated with the shifted objects.

#FIG. 1 is a simplified high-level block diagram of a conventional luminance-only based system adapted to detect color motion artifacts.

#FIG. 2 is an exemplary diagram of a color-motion artifacts caused by the system of FIG. 1.

#FIG. 3 is a simplified high-level block diagram of a system adapted to detect and reduce color-motion artifacts, in accordance with one embodiment of the present invention.

#In accordance with one aspect of the present invention, to detect color-motion artifacts in a video frame, a motion-compensated color-distance value is compared to a threshold value. If the motion-compensated color-distance value is greater than or equal to the threshold value, the video frame is identified as containing color-motion artifacts. In accordance with another aspect, to detect color-motion artifacts in a video frame, chroma and luma components of the intra-frame activity levels of a video frame are compared to chroma and luma components of the inter-frame activity levels for that video frame. If any of the components of the inter-frame activity levels is greater than the corresponding component of the intra-frame activity levels, the video frame is identified as containing color motion artifacts. In accordance with another aspect, to reduce any color-motion artifacts, either (1) a smaller quantization scale or (2) data is encoded using intra-frame encoding.

#Motion-Compensated Color-Difference Value

#To detect color-motion artifacts in each block of a video frame, first a motion-compensated color-distance value for that block (alternatively referred to hereinbelow as the current block or the underlying block) is computed, as described further below. Assume that the red, green and blue components of a video signal associated with a pixel disposed at coordinates (i,j) of the current block of a video frame are respectively represented by r(i,j), g(i,j), and b(i,j). Assume further that the red, green and blue components of a video signal associated with a pixel disposed at coordinates (i,j) of a corresponding block of a reference frame is represented by r′(i,j), g′(i,j), and b′(i,j). In accordance with the present invention, the motion-compensated color-difference value D is computed using the following equation: