Nested SEI Constraints for Accurate VVC Subpicture Extraction
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Solution Overview
Problem
The existing VVC design for specifying and signaling nested SEI messages for subpicture sequences has issues with the persistence of subpicture IDs, inclusion of filler payload, incorrect flag settings, and lack of constraints for associating SEI messages, leading to potential errors and inefficiencies in bitstream extraction.
Innovation Solution
The proposed solution involves using subpicture indices instead of IDs, prohibiting filler payload, enforcing specific flag settings for SLI messages, and adding constraints on SEI message types and NAL unit types to ensure correct association and extraction of SEI messages, thereby improving bitstream conformance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If subpicture IDs are used to associate SEI messages with subpictures, then the association can be established, but the persistence scope becomes limited and errors can occur when subpicture IDs change within a CLVS
Solution Approach 1:
The patent changes the parameter used for association from subpicture ID to subpicture index. The subpicture index provides a persistent identifier that remains valid across the entire CLVS, whereas subpicture ID changes within a CLVS. This parameter change resolves the contradiction by maintaining reliable association while extending the persistence scope to the entire coded video sequence.
2Adaptability or versatility
If filler payload SEI messages are allowed in scalable nesting SEI messages, then more flexibility is provided, but extraction errors occur when subpictures are removed
Solution Approach 1:
The patent extracts filler payload SEI messages from the scalable nesting SEI message structure. By prohibiting filler payload messages in scalable nesting SEI messages, the patent removes the source of extraction errors that occur when subpictures are removed, while maintaining the ability to include necessary SEI messages for proper video decoding.
Solution Approach 2:
The patent applies preliminary anti-action by prohibiting filler payload messages before extraction errors can occur. This preventive measure ensures that when subpictures are removed from a CLVS, there are no filler payload messages to cause extraction errors, thereby maintaining reliability without compromising the inclusion of essential SEI messages.
3Measurement precision
If correct flag settings are enforced for SLI messages, then extraction accuracy is improved, but the device complexity increases due to additional constraints
Solution Approach 1:
The patent applies preliminary action by establishing correct flag settings for SLI messages in advance, before extraction operations occur. By requiring that the sn_subpic_flag be set to 1 and the sn_ols_flag be set to 0 for SLI messages, the patent ensures accurate extraction without requiring complex runtime validation, thus improving precision without significantly increasing device complexity.
4Reliability
If constraints on SEI message types are added to scalable nesting messages, then bitstream conformance is improved, but the message structure complexity increases
Solution Approach 1:
The patent applies local quality by imposing specific constraints on SEI message types within scalable nesting SEI messages. By requiring that only certain SEI message types (BP, PT, DUI, SLI) be contained in scalable nesting SEI messages, the patent improves bitstream conformance with targeted local constraints rather than overall structural complexity, allowing the message structure to remain flexible for valid message types.
Data Source
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AI summary
Several techniques for video encoding and video decoding are described. An example method of processing video data includes performing a conversion between a video and a bitstream of the video, wherein the conversion is performed according to a format rule that specifies that a supplemental enhancement information network abstraction layer unit includes a network abstraction layer unit type equal to a prefix supplemental enhancement information network abstraction layer unit type in response to the supplemental enhancement information network abstraction layer unit including a scalable nesting supplemental enhancement information message that includes a supplemental enhancement information message not associated with a particular payload type.