Quantization adjustments for DC shift artifacts
First Claim
Patent Images
1. In a video encoder, a method comprising:
- computing plural transform coefficients for each of plural blocks in a video picture;
identifying one or more portions of the video picture that contain DC shift blocks by identifying one or more gradient slope regions in the video picture and analyzing quantization effects on DC coefficients for one or more of the plural blocks in the one or more gradient slope regions;
adjusting quantization for the video picture to reduce contouring artifacts when the video picture is reconstructed; and
outputting encoded data for the video picture, wherein the identifying the one or more portions of the video picture that contain DC shift blocks includes checking a predetermined list of DC coefficient values exhibiting DC shift artifacts at a given quantization step size.
2 Assignments
0 Petitions
Accused Products
Abstract
A video encoder identifies one or more portions of a video picture that contain DC shift blocks and adjusts quantization (e.g., by selecting a smaller quantization step size) to reduce contouring artifacts when the picture is reconstructed. The encoder can identify the portion(s) of the picture that contain DC shift blocks by identifying one or more gradient slope regions in the picture and analyzing quantization effects on DC coefficients in the gradient slope region(s). The encoder can select a coarser quantization step size for a high-texture picture portion.
-
Citations
20 Claims
-
1. In a video encoder, a method comprising:
-
computing plural transform coefficients for each of plural blocks in a video picture; identifying one or more portions of the video picture that contain DC shift blocks by identifying one or more gradient slope regions in the video picture and analyzing quantization effects on DC coefficients for one or more of the plural blocks in the one or more gradient slope regions; adjusting quantization for the video picture to reduce contouring artifacts when the video picture is reconstructed; and outputting encoded data for the video picture, wherein the identifying the one or more portions of the video picture that contain DC shift blocks includes checking a predetermined list of DC coefficient values exhibiting DC shift artifacts at a given quantization step size. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
-
-
11. In a video encoder, a method comprising:
-
computing plural transform coefficients for each of plural blocks in a video picture; identifying one or more portions of the video picture that contain DC shift blocks by identifying one or more gradient slope regions in the video picture and analyzing quantization effects on DC coefficients for one or more of the plural blocks in the one or more gradient slope regions; adjusting quantization for the video picture to reduce contouring artifacts when the video picture is reconstructed; and outputting encoded data for the video picture, wherein the identifying the one or more portions of the video picture that contain DC shift blocks includes; identifying the DC shift blocks; identifying one or more gradient slope regions; and for one of the DC shift blocks in one of the one or more gradient slope regions, checking if any neighbor block both is smooth and has a lower or higher DC coefficient value. - View Dependent Claims (12, 13, 14, 15, 16, 17)
-
-
18. A computer-readable memory device for executing a method, the method comprising:
-
computing plural transform coefficients for each of plural blocks in a video picture; identifying one or more portions of the video picture that contain DC shift blocks by identifying one or more gradient slope regions in the video picture and analyzing quantization effects on DC coefficients for one or more of the plural blocks in the one or more gradient slope regions; adjusting quantization for the video picture to reduce contouring artifacts when the video picture is reconstructed; and outputting encoded data for the video picture, wherein the identifying the one or more portions of the video picture that contain DC shift blocks includes checking a predetermined list of DC coefficient values exhibiting DC shift artifacts at a given quantization step size. - View Dependent Claims (19, 20)
-
Specification