VVC Sub-Bitstream Extraction With AUD and SEI Conformance
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Solution Overview
Problem
The existing sub-bitstream extraction process in VVC standards faces issues such as incorrect specification of tIdTarget range, removal of access unit delimiters, improper handling of SEI messages, and inconsistencies in SEI message extraction and inclusion, leading to non-conforming bitstreams.
Innovation Solution
Specify tIdTarget within the range of 0 to vps_max_sublayers_minus1, treat AUD NAL units similarly to other types, refine SEI message extraction to include only applicable non-scalable-nested messages, and ensure SEI NAL units contain consistent payload types, addressing issues in the sub-bitstream extraction process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing sub-bitstream extraction process is used, then the extraction can be performed quickly, but the generated bitstream does not conform to the specification requirements
Solution Approach 1:
The extraction process is divided into distinct steps: identifying NAL units by type and TemporalId, filtering based on conformance rules, and constructing the output sub-bitstream. This segmentation allows each aspect (AUD unit handling, SEI unit removal, TemporalId validation) to be handled independently according to specific rules, ensuring conformance without excessive complexity
Solution Approach 2:
The patent applies specific parameter constraints during extraction: maximum TemporalId value is enforced (e.g., TemporalId ≤ 1 for certain profiles), AUD NAL units are treated consistently regardless of layer, and SEI NAL units are removed based on payload type analysis. These parameter changes ensure the extracted bitstream conforms to specification requirements
2Quantity of substance
If SEI NAL units are removed from the bitstream, then the bitstream size is reduced, but important supplemental information may be lost
Solution Approach 1:
The patent applies different handling rules to different SEI NAL units based on their local characteristics (payload type). Certain payload types are removed while others are preserved, allowing the system to reduce bitstream size by removing redundant SEI units while maintaining conformant information. The decision to remove or keep each SEI unit is made locally based on its payload type and conformance requirements
3Adaptability or versatility
If AUD NAL units are handled differently across layers, then layer-specific information is preserved, but the extraction process becomes inconsistent and complex
Solution Approach 1:
The patent establishes a universal rule for handling AUD NAL units: they are treated consistently across all layers and are not removed during extraction. This universal approach simplifies the extraction process by eliminating the need for complex layer-specific AUD handling logic, while still preserving the necessary access unit delimiter information in the output sub-bitstream
Data Source
AI summary
Examples of video encoding methods and apparatus and video decoding methods and apparatus are described. An example method of video processing includes performing a conversion between a video including multiple layers and a bitstream of the video according to a rule, wherein the rule specifies that, in a first process of sub-bitstream extraction to output a first output sub-bitstream, the first output sub-bitstream is extracted without removing network abstraction layer (NAL) units of a particular type and having a particular NAL unit header identifier value, and wherein the particular type includes an access unit delimiter (AUD) NAL unit.