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AssigneeMicrosoft Corporation
InventorsShankar Regunathan, Shijun Sun, Chengjie Tu, Chih-Lung Lin
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Techniques and tools for encoding enhancement layer video with quantization that varies spatially and/or between color channels are presented, along with corresponding decoding techniques and tools. For example, an encoding tool determines whether quantization varies spatially over a picture, and the tool also determines whether quantization varies between color channels in the picture. The tool signals quantization parameters for macroblocks in the picture in an encoded bit stream. In some implementations, to signal the quantization parameters, the tool predicts the quantization parameters, and the quantization parameters are signaled with reference to the predicted quantization parameters. A decoding tool receives the encoded bit stream, predicts the quantization parameters, and uses the signaled information to determine the quantization parameters for the macroblocks of the enhancement layer video. The decoding tool performs inverse quantization that can vary spatially and/or between color channels.
A computing device comprising a processing unit, memory and a storage medium storing computer-executable instructions which, when executed, cause the computing device to perform a method comprising:
In a computing device that implements a video decoder, a method comprising:
A computing device comprising a processing unit, memory and a storage medium storing computer-executable instructions which, when executed, cause the computing device to perform a method comprising:
Dependencies are inferred from the claim text.
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Quantisation: details of normalisation or weighting functions, e.g. normalisation matrices or variable uniform quantisers
Characterised by the element, parameter or selection affected or controlled by the adaptive coding: quantisation
The unit being an image region, e.g. an object: the region being a picture, frame or field
The unit being an image region, e.g. an object: the region being a block, e.g. a macroblock
About 4 years of term left · ends 22 Oct 2030 (estimated)
Engineers use compression (also called coding or encoding) to reduce the bit rate of digital video. Compression decreases the cost of storing and transmitting video by converting the video into a lower bit rate form. Decompression (also called decoding) reconstructs a version of the original video from the compressed form. A “codec” is an encoder/decoder system.
Generally, much of the bit rate reduction from compression is achieved through quantization. According to one possible definition, quantization is a term used for an approximating non-reversible mapping function commonly used for lossy compression, in which there is a specified set of possible output values, and each member of the set of possible output values has an associated set of input values that result in the selection of that particular output value. A variety of quantization techniques have been developed, including scalar or vector, uniform or non-uniform, with or without dead zone, and adaptive or non-adaptive quantization.
In many implementations, an encoder performs quantization essentially as a biased division of an original data value by a quantization factor. One or more quantization parameters (QPs) indicate the quantization factor for purposes of inverse quantization of the data value. For inverse quantization, often implemented as a multiplication operation, an encoder or decoder reconstructs a version of the data value using the quantization factor indicated by the QP(s). Quantization typically introduces loss in fidelity to the original data value, which can show up as compression errors or artifacts in the results of decoding.
FIG. 1 is a block diagram of a suitable computing environment in which several described embodiments may be implemented.
FIG. 2 is a block diagram of an exemplary encoding system for encoding a picture of enhancement layer video quantized with one or more QPs that vary spatially and/or across color channels of the picture.
FIG. 3 is a block diagram of an exemplary decoding system for decoding a picture of enhancement layer video quantized with one or more QPs that vary spatially and/or across color channels of the picture.
Techniques and tools for adapting quantization spatially and from color channel-to-channel are described herein. Depending on implementation, adapting quantization spatially and across color channels of enhancement layer video can help improve scalable video coding performance in several respects, especially for high-fidelity encoding of high bit depth video.
Many base layer video encoders adapt quantization spatially. When enhancement layer video represents quality differences between reconstructed base layer video and the original video, the energy of the signal in the enhancement layer can vary roughly in proportion to the strength of adaptive quantization in the base layer. Adapting quantization of the enhancement layer video spatially helps improve encoding performance for the enhancement layer video.
Spatially adapting quantization of enhancement layer video can have other advantages. In some scalable video encoding/decoding systems, certain areas of enhancement layer video are predicted from base layer video, while other areas of the enhancement layer video are predicted from previously reconstructed enhancement layer video, for example, using motion compensation. Using different levels of quantization in the different areas of the enhancement layer video can improve performance by allowing the encoder to adapt to the characteristics of the different areas.