Video Bitstream Flags for Reference Picture Resampling Control
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Solution Overview
Problem
Existing video coding technologies struggle with efficiently handling changes in picture size and resolution within a coded video sequence, particularly in modern codecs like VVC, where adaptive resolution changes are not adequately signaled, leading to inefficiencies in reference picture resampling.
Innovation Solution
A method and device for decoding video bitstreams that utilize flags to indicate whether a constant picture size is used, and if not, obtain a conformance window size for determining a resampling ratio between the current and reference pictures, enabling efficient reference picture resampling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If adaptive resolution changes are implemented in modern video codecs, then flexibility in handling picture size changes is improved, but signaling complexity and computational overhead increase
Solution Approach 1:
The patent changes the parameter representation from absolute conformance window coordinates to a resampling ratio parameter. This allows the decoder to derive the conformance window size from the resampling ratio and reference picture size, reducing signaling overhead while maintaining adaptive resolution change capabilities.
Solution Approach 2:
The patent extracts the essential information needed for resampling (the ratio) rather than signaling all conformance window parameters explicitly. By taking out only the critical resampling ratio parameter, the patent reduces signaling complexity while preserving the ability to handle adaptive resolution changes.
2Measurement precision
If conformance window size is explicitly signaled for each picture, then precision in picture size control is improved, but bitrate overhead increases
Solution Approach 1:
The patent transforms the representation from explicit conformance window size parameters to a derived resampling ratio parameter. This parameter change maintains precision in picture size control because the conformance window can be accurately reconstructed from the resampling ratio and reference picture dimensions, while significantly reducing the number of bits required for signaling.
Solution Approach 2:
The resampling ratio acts as an intermediary parameter that connects the reference picture size to the current picture size. Instead of directly signaling the conformance window size, the patent uses this intermediate ratio parameter, which reduces bitrate overhead while preserving the ability to precisely control picture dimensions.
3Manufacturing precision
If reference picture resampling is performed for every picture size change, then decoding accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs reference picture resampling in advance, before the actual decoding process. By pre-computing the resampled reference pictures using the signaled resampling ratio, the patent ensures decoding accuracy is maintained while reducing the computational burden during the critical decoding phase. The pre-resampled pictures are then reused for multiple predictions.
Data Source
AI summary
A method of decoding an encoded video bitstream using at least one processor, including obtaining a first flag indicating whether a constant picture size is used in a coded video sequence including a current picture; based on the first flag indicating that the constant picture size is used, decoding the current picture without performing reference picture resampling; based on the first flag indicating that the constant picture size is not used, obtaining a second flag indicating whether a conformance window size is signaled; based on the second flag indicating that the conformance window size is signaled: obtaining the conformance window size, determining a resampling ratio between the current picture and a reference picture based on the conformance window size, and performing the reference picture resampling on the current picture using the resampling ratio.