Subpicture Bitstream Extraction With SEI and Parameter Set Rewriting
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Solution Overview
Problem
The existing subpicture sub-bitstream extraction process in VVC lacks clarity in handling SEI NAL units, subpicture indexing, and parameter rewriting, leading to inconsistencies and inefficiencies in extracting a conforming sub-bitstream.
Innovation Solution
Specify the removal of SEI NAL units containing scalable-nested SEI messages that do not apply, adjust subpicture indexing, and clearly define conditions for rewriting parameter sets such as sublayer_level_idc, cpb_size_value_minus1, bit_rate_value_minus1, and cbr_flag in the subpicture sub-bitstream extraction process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the subpicture sub-bitstream extraction process is implemented without clear rules for SEI NAL units, then the extraction can be performed, but inconsistencies and errors occur in the output bitstream
Solution Approach 1:
The patent extracts and removes SEI NAL units containing scalable-nested SEI messages that are not applicable to the output bitstream during the subpicture sub-bitstream extraction process. This extraction principle resolves the contradiction by selectively removing problematic elements (inapplicable SEI messages) to ensure output conformance while maintaining a manageable process through clear removal criteria based on applicability flags and subpicture index matching.
2Manufacturing precision
If subpicture indexing is not clearly defined across layers, then the extraction process can proceed, but indexing inconsistencies occur between layers with different numbers of subpictures per picture
Solution Approach 1:
The patent applies local quality by defining subpicture indexing rules that adapt to local conditions of different layers. Specifically, when a layer has multiple subpictures per picture, the subpicture index is used to identify the corresponding subpicture in the extracted bitstream. This localized indexing approach ensures precision in each layer's context without requiring a universally complex indexing system across all layer types.
Solution Approach 2:
The patent segments the bitstream into multiple layers, where each layer may have different numbers of subpictures per picture. By segmenting the processing into layer-specific extraction rules, the system achieves precise indexing within each segment while managing overall complexity through modular layer-by-layer processing.
3Reliability
If parameter sets are not selectively rewritten during extraction, then the process is simpler, but the output bitstream may contain incorrect or inapplicable parameter values
Solution Approach 1:
The patent performs preliminary actions by pre-defining rewriting rules for parameter sets before the actual extraction process. Conditions for rewriting parameters such as sublayer_level_idc, cpb_size_value_minus1, bit_rate_value_minus1, and cbr_flag are established in advance based on layer and subpicture characteristics. This preliminary setup ensures accurate parameter values in the output while managing complexity through pre-established conditional logic rather than ad-hoc modifications.
Data Source
AI summary
A method of processing video data includes performing a conversion between a video and a bitstream of the video. The bitstream includes one or more layers including one or more sublayers including one or more pictures including one or more subpictures according to a rule that specifies a rewriting operation selectively performed on one or more syntax structures during a subpicture sub-bitstream extraction process by which an output target sub-bitstream is extracted from the bitstream. The one or more syntax elements include information of the output target sub-bitstream.