Luma Mapping With Chroma Scaling Control During Gradual Decoding Refresh
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Solution Overview
Problem
Intra coded pictures in video coding technologies like AVC, HEVC, and VVC lead to increased encoder-to-decoder delay, making them unsuitable for ultra-low delay applications, and techniques like GDR face compatibility issues with luma mapping with chroma scaling (LMCS) during decoding.
Innovation Solution
Prevent luma mapping with chroma scaling decoding processes during GDR periods by setting specific flags to zero, and apply these prevention methods based on virtual boundaries and enabling values to ensure compatibility and reduce delay.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If luma mapping with chroma scaling (LMCS) is applied during GDR decoding, then decoding accuracy is improved, but compatibility issues arise and processing complexity increases
Solution Approach 1:
The patent extracts the LMCS decoding process from the GDR decoding workflow by introducing a flag that prevents LMCS from being applied when GDR is active. This separation resolves the compatibility conflict between LMCS and GDR while maintaining the benefits of both techniques where applicable.
Solution Approach 2:
The patent implements dynamic control of the LMCS process through a flag that can be enabled or disabled based on the decoding mode. This allows the system to adaptively switch between LMCS and non-LMCS modes depending on whether GDR is active, resolving the compatibility issue through dynamic configuration.
2Productivity
If LMCS decoding process is applied to all pictures, then processing completeness is improved, but decoding time increases due to additional processing steps
Solution Approach 1:
The patent applies LMCS only partially to pictures that do not require GDR processing. By using the flag to identify GDR pictures and excluding them from LMCS processing, the system avoids unnecessary processing steps while maintaining completeness for applicable pictures, thereby reducing overall decoding time.
3Loss of time
If GDR is used to reduce encoder-to-decoder delay, then delay is reduced, but compatibility with certain coding tools like LMCS deteriorates
Solution Approach 1:
The patent extracts the LMCS process from the GDR workflow by using a flag to prevent LMCS from executing when GDR is active. This extraction eliminates the compatibility conflict between GDR and LMCS while preserving the delay reduction benefit of GDR.
Solution Approach 2:
The patent implements dynamic adaptation by using a flag that adjusts the decoding behavior based on whether GDR is active. This dynamic control allows the system to maintain compatibility with GDR while still applying LMCS when appropriate, resolving the compatibility issue through adaptive configuration.
Data Source
AI summary
A method, apparatus, and computer program product provide for management of luma mapping with chroma scaling (LMCS) processes for Gradual Decoding Refresh (GDR) pictures. In the context of a method, the method accesses a picture to be decoded and determines whether the picture is within a GDR period. The method can also prevent a LMCS decoding process from being applied to the picture within the GDR period. Another method can determine whether a virtual boundary is within a current coding tree unit of a picture with a GDR period and if so, prevent a chroma residual scaling decoding process associated with LMCS from being applied to one or more coding units within a clean area. Another method can pad a neighboring pixel area from one or more reconstructed pixels in a clean area for a chroma residual scaling decoding process associated with LMCS.