Decoded Picture Buffer Management for Video Subpicture Extraction
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Solution Overview
Problem
Current video coding standards face challenges in efficiently signaling level information for subpicture sequences, particularly in the removal of decoded pictures from the decoded picture buffer and handling of supplemental enhancement information during subpicture extraction, which affects bitstream conformance and decoding processes.
Innovation Solution
The proposed solution involves modifying the video processing methods to signal DPB parameters in shared syntax structures, removing non-scalable-nested SEI messages during subpicture extraction, and rewriting sequence parameter sets to include subpicture ID mapping, ensuring correct derivation of picture order counts and bitstream conformance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decoded pictures are removed from the decoded picture buffer during subpicture extraction, then bitstream conformance is improved, but decoding complexity increases due to additional buffer management operations
Solution Approach 1:
The patent applies preliminary action by pre-determining which pictures should be removed from the decoded picture buffer based on subpicture extraction requirements. The buffer management decisions are made in advance during the extraction process rather than ad-hoc, allowing the decoder to efficiently manage buffer contents while maintaining bitstream conformance.
2Reliability
If supplemental enhancement information is removed during subpicture extraction, then bitstream conformance is improved, but information loss increases
Solution Approach 1:
The patent applies the extraction principle by selectively removing only the necessary supplemental enhancement information that is specific to the extracted subpicture portion. This targeted extraction removes redundant or inapplicable SEI messages while preserving essential information needed for correct decoding of the subpicture bitstream.
3Measurement precision
If sequence parameter sets are rewritten to include subpicture ID mapping, then decoding accuracy is improved, but processing overhead increases
Solution Approach 1:
The patent applies preliminary action by pre-computing and inserting the subpicture ID mapping into the sequence parameter sets before the actual subpicture extraction process. This preparation work is done once during initialization or parameter set parsing, avoiding repeated computations during extraction and minimizing processing overhead while ensuring decoding accuracy.
4Quantity of substance
If a single syntax structure is used for multiple output layer sets, then bitstream compactness is improved, but parameter signaling flexibility decreases
Solution Approach 1:
The patent applies universality by designing a single syntax structure that can serve multiple output layer sets simultaneously. This shared syntax structure contains parameters that are either common to all layer sets or can be appropriately interpreted for each specific layer set, reducing bitstream redundancy while maintaining the flexibility to signal different parameters for different layers when needed.
Data Source
AI summary
Embodiments for video encoding and video decoding are described. One example method includes performing a conversion between a video and a bitstream of the video, wherein the bitstream includes one or more pictures including one or more subpictures according to a rule, and wherein the rule specifies that, responsive to a condition, a rewriting operation is performed on referenced one or more sequence parameter sets during a subpicture sub-bitstream extraction process by which a target output sub-bitstream is extracted from the bitstream.