CfL Downsampling Filter Signaling for Consistent GOP Decoding
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Solution Overview
Problem
Current signaling approaches for downsampling filters in chroma from luma intra prediction mode result in inconsistent outcomes between sequential and parallel running of group of pictures and excessive redundant signaling overhead, particularly in inter-coded frames.
Innovation Solution
A method for signaling a downsampling filter in cross component intra prediction mode, involving retrieval of a syntax element for a key frame, downsampling luma blocks, and predicting chroma blocks based on downsampled frames, to improve decoding efficiency and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current signaling approaches are used for downsampling filters in CfL mode, then the filter can be signaled, but inconsistent outcomes occur between sequential and parallel running of GOPs
Solution Approach 1:
The patent applies preliminary action by signaling the downsampling filter type at the key frame level in advance, rather than at each individual frame level. This allows the filter type to be determined beforehand for all frames within a GOP, ensuring consistent decoding outcomes whether processed sequentially or in parallel, while reducing the overall signaling complexity.
2Manufacturing precision
If downsampling filter type is signaled at each frame level, then filtering can be applied, but redundant signaling overhead occurs particularly in inter-coded frames
Solution Approach 1:
The patent extracts the downsampling filter type signaling from the frame-level syntax and relocates it to the key frame-level syntax. This separation removes the redundant signaling overhead that would otherwise occur at every frame level, particularly in inter-coded frames where the filter type does not change, while preserving the necessary filtering precision through appropriate application of the signaled filter type.
3Adaptability or versatility
If multiple downsampling filters are supported, then coding flexibility is improved, but signaling overhead increases
Solution Approach 1:
The patent applies local quality by signaling the downsampling filter type at the key frame level rather than uniformly at every frame level. This localized approach maintains the adaptability to select different filter types for different key frames while reducing the overall signaling overhead, as the filter type remains constant for all frames within a GOP. The syntax element is included only when the filter type changes, optimizing the balance between flexibility and overhead.
Data Source
AI summary
The various implementations described herein include methods and systems for decoding video. An example method includes receiving a video stream having a sequence of frames. The sequence of frames includes one or more key frames. Each key frame has a respective downsampling filter type. The method includes, in accordance with a determination that a current frame corresponds to a first key frame, retrieving, from the video stream, a syntax element associated with a first downsampling filter type associated with the first key frame. The method includes a luma block of the current frame and a predefined set of frames immediately after the current frame using the first downsampling filter type to obtain downsampled frames. The method includes predicting a chroma block of the current frame based on the downsampled frames.