Adaptive B-picture quantization control
First Claim
Patent Images
1. In a video encoder, a method comprising:
- selecting a picture type for a current picture;
using the selected picture type when selecting between multiple available quantizers for the current picture, each of the multiple available quantizers having a different dead zone ratio, the selected quantizer for the current picture having a larger dead zone ratio than one or more other quantizers among the multiple available quantizers;
applying the selected quantizer to the current picture; and
outputting encoded data for the current picture.
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Abstract
The present application is directed to techniques and tools for adapting the quantizer as well as the quantization step size used during video encoding. For example, a video encoder uses a non-uniform quantizer (having a relatively large dead zone ratio) for B-picture types, but uses a uniform quantizer for other types of pictures. In many encoding scenarios, this helps the encoder control bit rate for the B-picture types instead of resorting to higher quantization step sizes, which improves overall quality for the B-picture types.
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Citations
20 Claims
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1. In a video encoder, a method comprising:
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selecting a picture type for a current picture;
using the selected picture type when selecting between multiple available quantizers for the current picture, each of the multiple available quantizers having a different dead zone ratio, the selected quantizer for the current picture having a larger dead zone ratio than one or more other quantizers among the multiple available quantizers;
applying the selected quantizer to the current picture; and
outputting encoded data for the current picture. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8)
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9. In a video encoder, a method comprising:
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getting a current picture of a video sequence;
if the current picture is a P-picture or an I-picture;
selecting a uniform quantizer with uniform dead zone for AC coefficients for the current picture; and
applying the selected uniform quantizer to the current picture;
if the current picture is a B-picture;
selecting a non-uniform quantizer with a non-uniform dead zone for AC coefficients for the current picture, wherein the non-uniform dead zone is larger than the uniform dead zone of the uniform quantizers; and
applying the selected non-uniform quantizer to the current picture; and
outputting encoded data for the current picture. - View Dependent Claims (10, 11, 12)
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13. An encoder comprising:
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a frequency transformer for frequency transforming plural blocks of spatial domain information into plural blocks of transform coefficients;
a quantizer for quantizing the transform coefficients;
an entropy encoder for entropy encoding the quantized transform coefficients;
an inverse quantizer for inverse quantizing the quantized transform coefficients; and
a controller for selecting quantizers and quantization step sizes for the quantizing by choosing between plural available quantizers, each of the plural available quantizers having a different dead zone ratio, wherein the controller implements;
a first path for increasing dead zone ratio while decreasing quantization step size for a given level of rate-distortion performance; and
a second path for decreasing dead zone ratio while increasing quantization step size for the given level of rate-distortion performance. - View Dependent Claims (14, 15, 16, 17, 18, 19, 20)
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Specification