Signaling Chroma Quantization Parameter Tables in Video Coding
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Solution Overview
Problem
The existing video coding standards, such as HEVC and VVC, face challenges in efficiently signaling and deriving chroma quantization parameter (QP) tables, leading to increased bit usage and potential waste of bits when signaling chroma QP tables for joint CbCr residuals, especially when the joint CbCr residual coding tool is not enabled.
Innovation Solution
The proposed solution introduces new syntax elements and signaling mechanisms to flexibly signal chroma QP tables, allowing for optional signaling of chroma QP tables only when necessary, using piece-wise linear functions, and reducing bit usage by signaling differences between input and output values of control points, thereby optimizing bit allocation for chroma QP mapping.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If chroma QP tables are signaled for joint CbCr residuals, then chroma QP mapping flexibility is improved, but bit overhead increases when joint CbCr residual coding tool is not enabled
Solution Approach 1:
The patent introduces dynamic signaling mechanisms where chroma QP table signaling is conditionally enabled or disabled based on the activation status of the joint CbCr residual coding tool. The decoder receives flags that dynamically control whether chroma QP table data is present in the bitstream, allowing the system to adapt its signaling behavior to current coding conditions and avoid unnecessary bit consumption when joint coding is not active.
Solution Approach 2:
The patent changes the parameter representation by signaling differences between input and output QP values rather than absolute values. This parameter transformation reduces the number of bits required to represent chroma QP table entries, as the differences are typically smaller and can be encoded more efficiently, thereby reducing overall bit overhead while maintaining mapping flexibility.
2Measurement precision
If chroma QP tables are always signaled, then chroma QP mapping accuracy is improved, but bit rate increases
Solution Approach 1:
The patent implements partial signaling where chroma QP tables are signaled only when necessary, specifically when the joint CbCr residual coding tool is enabled. Instead of always signaling complete chroma QP tables, the system selectively applies signaling based on current coding requirements, achieving sufficient mapping accuracy only when needed while reducing bit rate during normal operation.
Solution Approach 2:
The patent extracts and signals only the essential chroma QP information needed for accurate mapping, rather than transmitting complete QP tables unconditionally. By separating the signaling of chroma QP data from the general coding process and only including it when the joint CbCr tool is active, the system removes unnecessary bit consumption while preserving mapping accuracy when required.
3Quantity of substance
If chroma QP tables are not signaled, then bit rate is reduced, but chroma QP mapping flexibility deteriorates
Solution Approach 1:
The patent creates a dynamic signaling system where chroma QP table inclusion in the bitstream is controlled by conditional flags related to joint CbCr residual coding tool activation. This dynamic approach allows the system to maintain low bit rates during normal operation while automatically providing full chroma QP mapping flexibility when the joint coding tool is enabled, ensuring adaptability is preserved on demand.
Solution Approach 2:
The patent prepares chroma QP table signaling in advance by checking the activation status of the joint CbCr residual coding tool before encoding. This preliminary action allows the encoder to proactively include or exclude chroma QP table data based on future decoding requirements, ensuring that flexibility is available when needed without continuously increasing bit rate.
Data Source
AI summary
The present disclosure provides method and systems for signaling chroma quantization parameter (QP) table. According to some disclosed embodiments, the methods include: receiving a bitstream of video data; determining whether a luma-to-chroma QP mapping table is signaled, based on a first flag in the bitstream; and in response to the first flag being a first value, determining the signaled luma-to-chroma (P mapping table based on the bitstream.