DC coefficient signaling at small quantization step sizes
First Claim
1. A computer-implemented method of decoding video using a video decoder, the method comprising:
- receiving encoded data in a bit stream and decoding a video picture using the encoded data, including;
receiving a first code that indicates a value for a DC differential for a DC coefficient of a block of the video picture;
decoding the first code to determine the value for the DC differential;
receiving a second code that indicates a refinement of the value for the DC differential;
decoding the second code to determine the refinement of the value for the DC differential; and
reconstructing the DC differential using the value for the DC differential and the refinement, including adding the refinement to a multiple of the value for the DC differential, wherein the DC differential represents a difference of the DC coefficient from a DC predictor,wherein the multiple of the value for the DC differential is determined by multiplying the value for the DC differential by a factor that depends on quantization step size, andwherein;
if the quantization step size is 1, the factor is 4; and
if the quantization step size is 2, the factor is 2.
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Accused Products
Abstract
Described tools and techniques relate to signaling for DC coefficients at small quantization step sizes. The techniques and tools can be used in combination or independently. For example, a tool such as a video encoder or decoder processes a VLC that indicates a DC differential for a DC coefficient, a FLC that indicates a value refinement for the DC differential, and a third code that indicates the sign for the DC differential. Even with the small quantization step sizes, the tool uses a VLC table with DC differentials for DC coefficients above the small quantization step sizes. The FLCs for DC differentials have lengths that vary depending on quantization step size.
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Citations
18 Claims
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1. A computer-implemented method of decoding video using a video decoder, the method comprising:
receiving encoded data in a bit stream and decoding a video picture using the encoded data, including; receiving a first code that indicates a value for a DC differential for a DC coefficient of a block of the video picture; decoding the first code to determine the value for the DC differential; receiving a second code that indicates a refinement of the value for the DC differential; decoding the second code to determine the refinement of the value for the DC differential; and reconstructing the DC differential using the value for the DC differential and the refinement, including adding the refinement to a multiple of the value for the DC differential, wherein the DC differential represents a difference of the DC coefficient from a DC predictor, wherein the multiple of the value for the DC differential is determined by multiplying the value for the DC differential by a factor that depends on quantization step size, and wherein; if the quantization step size is 1, the factor is 4; and if the quantization step size is 2, the factor is 2. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A system for decoding video using a video decoder, the system comprising:
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memory means for storing program instructions; processor means operating to execute the program instructions in the memory means for receiving encoded data in a bit stream and decoding a video picture using the encoded data, including by; receiving a first code that indicates a value for a DC differential for a DC coefficient of a block of the video picture; decoding the first code to determine the value for the DC differential; receiving a second code that indicates a refinement of the value for the DC differential; decoding the second code to determine the refinement of the value for the DC differential; and reconstructing the DC differential using the value for the DC differential and the refinement, including adding the refinement to a multiple of the value for the DC differential, wherein the DC differential represents a difference of the DC coefficient from a DC predictor, wherein the multiple of the value for the DC differential is determined by multiplying the value for the DC differential by a factor that depends on quantization step size, and wherein; if the quantization step size is 1, the factor is 4; and if the quantization step size is 2, the factor is 2. - View Dependent Claims (8, 9, 10, 11, 12)
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13. A computer-readable storage medium having program instructions stored thereon for execution by a processing unit of a computer to perform a method of decoding video, the method comprising:
receiving encoded data in a bit stream and decoding a video picture using the encoded data, including by; receiving a first code that indicates a value for a DC differential for a DC coefficient of a block of the video picture; decoding the first code to determine the value for the DC differential; receiving a second code that indicates a refinement of the value for the DC differential; decoding the second code to determine the refinement of the value for the DC differential; and reconstructing the DC differential using the value for the DC differential and the refinement, including adding the refinement to a multiple of the value for the DC differential, wherein the DC differential represents a difference of the DC coefficient from a DC predictor, wherein the multiple of the value for the DC differential is determined by multiplying the value for the DC differential by a factor that depends on quantization step size, and wherein; if the quantization step size is 1, the factor is 4; and if the quantization step size is 2, the factor is 2. - View Dependent Claims (14, 15, 16, 17, 18)
Specification