Chroma Scaling from Luma Mapping Codewords to Cut Decode Delay
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Solution Overview
Problem
The computation of chroma scaling factors from estimated luma values introduces delay in video data transmission, complicating the processing and decoding of video signals.
Innovation Solution
A simplified method for determining chroma scaling factors independently of luma averages by using a fixed chroma scaling factor derived from the number of codewords and an offset value, eliminating the need for average luma calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If chroma scaling factor is determined from estimated luma values, then chroma scaling accuracy is improved, but processing delay increases
Solution Approach 1:
The patent extracts the chroma scaling factor determination from the luma average calculation process. Instead of computing chroma scaling factors based on estimated luma values (which requires complex averaging operations), the invention derives chroma scaling factors directly from the piecewise linear mapping function parameters (breakpoints and slopes) that are already being used for luma mapping. This separation eliminates the dependency on luma average computations while maintaining chroma scaling accuracy.
Solution Approach 2:
The patent performs preliminary computation of chroma scaling factors using the piecewise linear mapping function parameters before actual chroma scaling is needed. By pre-calculating scaling factors based on the mapping function breakpoints and slopes during the luma mapping setup phase, the system avoids real-time computation delays during chroma processing, thus reducing overall processing delay while maintaining accuracy.
2Loss of time
If chroma scaling factor is determined independently of luma average, then processing delay is reduced, but chroma scaling accuracy may deteriorate
Solution Approach 1:
The patent changes the parameters used for chroma scaling factor determination from luma average values to piecewise linear mapping function parameters (breakpoints and slopes). By using the mapping function parameters that define the luma transformation, the invention maintains chroma scaling accuracy through a different mathematical basis that is equally informative about the luma characteristics without requiring average computations.
Solution Approach 2:
The piecewise linear mapping function parameters serve dual purposes: they define the luma mapping transformation and simultaneously provide the basis for chroma scaling factor determination. This multi-functionality allows the system to derive accurate chroma scaling factors from the same parameters used for luma mapping, eliminating the need for separate luma average calculations while maintaining accuracy.
Data Source
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AI summary
Systems and methods related to image encoding and decoding. One example is directed to an image decoder. The image decoder includes an electronic processor configured to receive encoded image data, determine, from the encoded image data, a chroma scaling factor independent of a luma average of the encoded image data and based on a number of codewords related to a forward mapping function of the encoded image data and a chroma offset factor, decode the encoded image data according to the chroma scaling factor to create decoded image data, and output the decoded image data.