DC coefficient signaling at small quantization step sizes
First Claim
1. A method of coding/decoding video, the method comprising, with a computing device that implements a video encoder and/or video decoder:
- determining a quantization step size, wherein one or more syntax elements in a bit stream indicate the quantization step size;
processing a variable length code (VLC) for a DC differential for a DC coefficient using a VLC table that includes different VLC values associated with different values for the DC differential, wherein the VLC table further includes an escape code that indicates presence of a fixed length code (FLC) for the DC differential for the DC coefficient; and
when the VLC is the escape code;
using the quantization step size to determine a length of the FLC for the DC differential for the DC coefficient, wherein the length of the FLC varies depending on the quantization step size; and
processing the FLC for the DC differential for the DC coefficient.
1 Assignment
0 Petitions
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.
-
Citations
29 Claims
-
1. A method of coding/decoding video, the method comprising, with a computing device that implements a video encoder and/or video decoder:
-
determining a quantization step size, wherein one or more syntax elements in a bit stream indicate the quantization step size; processing a variable length code (VLC) for a DC differential for a DC coefficient using a VLC table that includes different VLC values associated with different values for the DC differential, wherein the VLC table further includes an escape code that indicates presence of a fixed length code (FLC) for the DC differential for the DC coefficient; and when the VLC is the escape code; using the quantization step size to determine a length of the FLC for the DC differential for the DC coefficient, wherein the length of the FLC varies depending on the quantization step size; and processing the FLC for the DC differential for the DC coefficient. - View Dependent Claims (2, 3, 4, 5, 6, 22, 23, 24)
-
-
7. A computer-implemented method of decoding video using a computing device that implements a video decoder, the method comprising, with the computing device that implements the video decoder:
-
determining a quantization step size for a block of a video picture based on one or more syntax elements in a bit stream; receiving a variable length code (VLC) in the bit stream, wherein the VLC at least in part indicates a DC differential for a DC coefficient of the block of the video picture; determining that the VLC indicates an escape code in a VLC table, the escape code indicating presence in the bit stream of a fixed length code (FLC) for the DC differential, the VLC table also including different VLC values associated with different values for DC differentials; using the quantization step size to determine a length of the FLC for the DC differential in the bit stream, wherein the length of the FLC varies depending on the quantization step size; receiving the FLC in the bit stream; and decoding the FLC to determine a value for the DC differential; and reconstructing the DC coefficient using the value for the DC differential, wherein the DC differential represents a difference between the DC coefficient and a DC predictor. - View Dependent Claims (8, 9, 10, 11, 12, 13, 25)
-
-
14. A computing device comprising a processor and memory, wherein the computing device implements a video decoder configured to perform operations comprising:
-
determining a quantization step size for a block of a video picture based on one or more syntax elements in a bit stream; receiving a variable length code (VLC) in the bit stream, wherein the VLC at least in part indicates a DC differential for a DC coefficient of the block of the video picture; determining that the VLC indicates an escape code in a VLC table, the escape code indicating presence in the bit stream of a fixed length code (FLC) for the DC differential, the VLC table also including different VLC values associated with different values for DC differentials; using the quantization step size to determine a length of the FLC for the DC differential in the bit stream, wherein the length of the FLC varies depending on the quantization step size; receiving the FLC in the bit stream; decoding the FLC to determine a value for the DC differential; and reconstructing the DC coefficient using the value for the DC differential, wherein the DC differential represents a difference between the DC coefficient and a DC predictor. - View Dependent Claims (15, 16, 17, 18, 19, 20, 26)
-
-
21. One or more computer-readable memory devices storing computer-executable instructions for causing a computer system programmed thereby to perform decoding operations comprising:
-
determining a quantization step size for a block of a video picture based on one or more syntax elements in a bit stream; receiving a variable length code (VLC) in the bit stream, wherein the VLC at least in part indicates a DC differential for a DC coefficient of the block of the video picture; determining that the VLC indicates an escape code in a VLC table, the escape code indicating presence in the bit stream of a fixed length code (FLC) for the DC differential, the VLC table also including different VLC values associated with different values for DC differentials; using the quantization step size to determine a length of the FLC for the DC differential in the bit stream, wherein the length of the FLC varies depending on the quantization step size; receiving the FLC in the bit stream; decoding the FLC to determine a value for the DC differential; and reconstructing the DC coefficient using the value for the DC differential, wherein the DC differential represents a difference between the DC coefficient and a DC predictor. - View Dependent Claims (27, 28, 29)
-
Specification