Patent ID: 7511766

Claim:
A video signal processing device comprising a horizontal-direction processor which processes a frame image in a quantized video signal in a horizontal direction and a vertical-direction processor which processes the frame image in a vertical direction, the horizontal-direction processor comprising: first comparator configured to compare sequentially pixel values of two pixels in the frame image which are adjacent to each other in the horizontal direction; first region detector configured to detect a region in which a difference between the pixel values compared by the first comparator is within a specified range; first determining unit configured to, if a difference or the level of a change in pixel value between two pixels adjacent to each other across a horizontal boundary of the region detected by the first region detector is within a specified range, determine the horizontal boundary to be a step in the gradation region or if the difference or the level of a change is out of the specified range, determine the horizontal boundary to be a boundary of another region; and first gray level corrector configured to correct gray levels adjacent to each other across the horizontal boundary if the first determining unit determines the horizontal boundary to be a step in the gradation region, the vertical-direction processor comprising: second comparator to compare sequentially pixel values of two pixels in the frame image which are adjacent to each other in the vertical direction; second region detector to detect a region in which a difference between the pixel values compared by the second comparing means is within a specified range; second determining unit configured to, if a difference or the level of a change in pixel value between two pixels adjacent to each other across a vertical boundary of the region detected by the second region detector is within a specified range, determining the vertical boundary to be a step in the gradation region or if the difference or the level of a change is out of the specified range, determining the vertical boundary to be a boundary of another region; and second gray level corrector configured to correct gray levels adjacent to each other across the vertical boundary if the second determining unit determines the vertical boundary to be a step in the gradation region.