Multi-Layer Video Sub-Bitstream Extraction With SEI Handling
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Solution Overview
Problem
The existing sub-bitstream extraction process in VVC has issues such as incorrect handling of temporal ID ranges, removal of unnecessary NAL units, and improper management of SEI messages, leading to non-conforming bitstreams and inefficiencies in multi-layer video coding.
Innovation Solution
The process is refined to correctly handle temporal ID ranges, manage NAL units like AUD, and handle SEI messages by specifying conditions for removal and extraction, ensuring conforming bitstreams are produced.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing sub-bitstream extraction process is used, then the extraction speed is fast, but the bitstream conformance is incorrect due to improper handling of temporal ID ranges and SEI messages
Solution Approach 1:
The extraction process is divided into distinct steps: identifying VCL NAL units, determining temporal ID ranges, selectively removing NAL units based on layer identifiers, and conditional SEI message handling. This segmentation allows each step to be optimized independently while maintaining overall conformance.
Solution Approach 2:
The method performs preliminary identification of VCL NAL units and their temporal ID ranges before actual removal operations. SEI messages are pre-analyzed to determine which ones should be retained or removed, ensuring conformance requirements are met before final bitstream generation.
2Loss of information
If all SEI NAL units are removed during extraction, then the extraction process is simple, but important supplemental information is lost
Solution Approach 1:
Different SEI messages are treated differently based on their specific properties and relevance to the extraction context. Some SEI messages are preserved while others are removed, with the decision based on local characteristics of each message type and its relationship to the temporal ID ranges being extracted.
Solution Approach 2:
The extraction process dynamically adjusts which SEI messages to retain based on parameters such as temporal ID ranges, layer identifiers, and message types. This parameter-driven approach allows selective preservation of important information while removing unnecessary data.
3Reliability
If the extraction process handles all edge cases correctly, then bitstream conformance is ensured, but the processing time increases
Solution Approach 1:
The method performs exactly the necessary conformance checks and removal operations without over-processing. By identifying precise temporal ID ranges and layer identifier conditions, the process applies actions only where needed, avoiding unnecessary processing time while ensuring all conformance requirements are met.
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 and a bitstream of the video according to a rule, wherein the bitstream includes network abstraction layer (NAL) units for multiple video layers according to a rule; wherein the rule defines that a sub-bitstream extraction process to generate an output bitstream comprising an output layer set (OLS) includes one or more operations that are selectively performed responsive to the following conditions: (1) a list of NAL unit header layer identifier values in the OLS does not includes all values of NAL unit header layer identifiers in all video coding layer (VCL) NAL units in the bitstream, and (2) the output bitstream containing a supplemental enhancement information (SEI) NAL unit that contains a scalable-nesting SEI message.