	US 7,511,766 B2
	Video signal processing device and method for processing gradation step
Eiki Obara, Hiki-gun (Japan)
Assigned to Kabushiki Kaisha Toshiba, Tokyo (Japan)
Filed on Nov. 15, 2005, as Appl. No. 11/273,997.
Claims priority of application No. 2004-346557 (JP), filed on Nov. 30, 2004.
Prior Publication US 2006/0115173 A1, Jun. 01, 2006
Int. Cl. H04N 5/14 (2006.01)

U.S. Cl. 348—571 [348/671]

6 Claims

1. 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.