Fractional quantization step sizes for high bit rates
AssigneeMicrosoft Technology Licensing, LLC
InventorsThomas W. Holcomb, Sridhar Srinivasan, Pohsiang Hsu, Chih-Lung Lin
Life of this patent
Estimating the term…
Abstract
A video codec uses fractional increments of quantization step size at high bit rates to permit a more continuous variation of quality and/or bit rate as the quantization scale changes. For high bit rate scenarios, the bit stream syntax includes an additional syntax element to specify fractional step increments (e.g., half step) of the normal quantizer scale step sizes.
Claims20
In a computer system that implements a video decoder, a method comprising:
- decoding a quantizer index for a given frame of a video sequence, wherein the quantizer index indicates a picture quantizer scale for the given frame;
- comparing the quantizer index to a comparison value;
- responsive to the quantizer index being less than or equal to the comparison value, decoding a half-step quantization parameter field, the half-step quantization parameter field indicating a half-step increment for the picture quantizer scale for the given frame, and selectively adjusting the picture quantizer scale for the given frame according to the half-step increment, wherein syntax of the bitstream allows half-step picture quantization step sizes as specified by the quantizer index and the half-step quantization parameter field when the quantizer index is less than or equal to the comparison value but allows only integer-step picture quantization step sizes as specified by the quantizer index when the quantizer index is greater than the comparison value;
- inverse quantizing at least some quantized transform coefficients for blocks of the given frame;
- and
- based at least in part on the inverse-quantized transform coefficients, reconstructing the blocks of the given frame.
One or more computer-readable memory or storage devices having stored thereon computer-executable instructions for causing one or more processing units, when programmed thereby, to perform operations comprising:
- decoding a quantizer index for a given frame of a video sequence, wherein the quantizer index indicates a picture quantizer scale for the given frame;
- comparing the quantizer index to a comparison value;
- responsive to the quantizer index being less than or equal to the comparison value, decoding a half-step quantization parameter field, the half-step quantization parameter field indicating a half-step increment for the picture quantizer scale for the given frame, and selectively adjusting the picture quantizer scale for the given frame according to the half-step increment, wherein syntax of the bitstream allows half-step picture quantization step sizes as specified by the quantizer index and the half-step quantization parameter field when the quantizer index is less than or equal to the comparison value but allows only integer-step picture quantization step sizes as specified by the quantizer index when the quantizer index is greater than the comparison value;
- inverse quantizing at least some quantized transform coefficients for blocks of the given frame;
- and
- based at least in part on the inverse-quantized transform coefficients, reconstructing the blocks of the given frame.
A computer system comprising memory and one or more processing units, wherein the computer system implements a video decoder configured to perform operations comprising:
- decoding a quantizer index for a given frame of a video sequence, wherein the quantizer index indicates a picture quantizer scale for the given frame;
- comparing the quantizer index to a comparison value;
- responsive to the quantizer index being less than or equal to the comparison value, decoding a half-step quantization parameter field, the half-step quantization parameter field indicating a half-step increment for the picture quantizer scale for the given frame, and selectively adjusting the picture quantizer scale for the given frame according to the half-step increment, wherein syntax of the bitstream allows half-step picture quantization step sizes as specified by the quantizer index and the half-step quantization parameter field when the quantizer index is less than or equal to the comparison value but allows only integer-step picture quantization step sizes as specified by the quantizer index when the quantizer index is greater than the comparison value;
- inverse quantizing at least some quantized transform coefficients for blocks of the given frame;
- and
- based at least in part on the inverse-quantized transform coefficients, reconstructing the blocks of the given frame.
Dependencies are inferred from the claim text.