Chroma Block Prediction with Filter-Aligned Luma Downsampling
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Solution Overview
Problem
Current video coding standards face challenges in improving coding efficiency for the chroma component during intra prediction, particularly in high-definition video encoding.
Innovation Solution
A chroma block prediction method using a linear model mode (LM mode) is employed, where the encoder determines a filter type based on the sample position type of the chroma block and encodes indication information into a bitstream, allowing both encoder and decoder to align luma downsampling filters with chroma sample positions, thereby enhancing coding accuracy and efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a linear model mode with filter type indication is used for chroma block prediction, then coding accuracy and efficiency are improved, but device complexity increases due to additional filter alignment operations
Solution Approach 1:
The patent applies parameter changes by introducing filter type indication information that specifies different downsampling filter configurations. The encoder determines the appropriate filter type based on chroma block characteristics and signals this parameter to the decoder, allowing dynamic adjustment of filtering parameters to optimize coding accuracy for different content types while managing complexity through parameterized control.
Solution Approach 2:
The patent implements preliminary action by having the encoder pre-determine and signal the filter type indication information before the actual chroma block prediction process. This allows the decoder to prepare the appropriate downsampling filter in advance, ensuring both encoder and decoder use identical filter configurations without requiring complex real-time synchronization during decoding.
2Measurement precision
If filter type indication information is encoded into the bitstream, then encoder and decoder can align luma downsampling filters with chroma sample positions, but loss of information increases due to additional bitstream data
Solution Approach 1:
The patent applies local quality by encoding filter type indication information selectively based on chroma block characteristics. Rather than applying a uniform filtering approach to all chroma blocks, the encoder determines the appropriate filter type for each block or group of blocks based on local content properties, signaling only the necessary filter type information to achieve optimal local coding accuracy while minimizing overall bitstream overhead.
Solution Approach 2:
The patent implements partial action by encoding filter type indication information only when it provides beneficial coding improvement. The encoder can choose to signal filter type information selectively for certain chroma blocks where it matters most, rather than for all blocks, thereby achieving the necessary filter alignment for critical regions while reducing the overall information overhead in the bitstream.
Data Source
AI summary
The present disclosure provides a chroma block prediction method and a device. The method includes: parsing a bitstream to obtain first indication information; downsampling a first luma block by a first filter when a value of the first indication information is a first value or by using a second filter when a value of the first indication information is a second value, to obtain a second luma block; obtaining a plurality of chroma samples and a plurality of luma samples; obtaining linear model coefficients based on the plurality of chroma samples and the plurality of luma samples; and obtaining a prediction value of the current chroma block based on the second luma block and the linear model coefficients.