VVC Subpicture Track NAL Unit Ordering for Reliable Decoding
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Solution Overview
Problem
The VVC video file format faces issues in efficiently carrying and reconstructing subpictures across multiple tracks, particularly in ensuring subpictures are motion-constrained, contiguous in decoding order, and correctly ordering non-VCL NAL units, which affects the delivery and rendering of VVC video in streaming applications.
Innovation Solution
The proposed solution involves modifying the VVC video file format to require subpicture tracks to cover rectangular areas, allowing subpictures to be motion-constrained, and specifying the order of non-VCL NAL units in the base track to ensure correct reconstruction of video units, disallowing certain non-VCL NAL units in subpicture tracks, and removing unnecessary flexibility in subpicture order sample groups.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If subpicture tracks are allowed to contain flexible ordering of non-VCL NAL units, then adaptability in track composition is improved, but decoding reliability and reconstruction accuracy deteriorate due to ambiguous ordering
Solution Approach 1:
The patent changes the parameter of NAL unit ordering from flexible/ambiguous to fixed/deterministic by specifying that non-VCL NAL units must be placed after VCL NAL units in subpicture tracks. This parameter change resolves the contradiction by establishing a clear ordering rule that maintains decoding reliability while preserving track composition adaptability through the track reference mechanism.
2Productivity
If subpictures are allowed in multiple separate tracks, then bandwidth utilization and parallel processing are improved, but reconstruction complexity and potential errors increase
Solution Approach 1:
The patent introduces a base track as an intermediary that references subpicture tracks. The base track contains the primary video content while subpicture tracks contain additional subpicture data. This intermediary structure enables parallel processing of multiple tracks while simplifying reconstruction by providing a central coordination point that manages the integration of data from multiple sources through track references.
3Manufacturing precision
If motion-constrained subpictures are enforced across track boundaries, then rendering accuracy is improved, but data transmission overhead increases
Solution Approach 1:
The patent segments video content into base track data and subpicture track data, where subpictures are motion-constrained and can be independently processed. By dividing the content into segments that can be independently encoded and transmitted, the system achieves motion-constrained rendering accuracy while reducing overall transmission overhead through efficient partitioning of data that can be selectively decoded.
Data Source
AI summary
Systems, methods and apparatus for processing visual media data are described. One example method includes performing a conversion between visual media data and a visual media file that includes one or more tracks that store one or more bitstreams of the visual media data according to a format rule; wherein the visual media file includes a base track that references one or more subpicture tracks, and wherein the format rule specifies an order of non-VCL (video coding layer) NAL (network abstraction layer) units in a sample of the base track in reconstructing a video unit from the sample of the base track and samples in the one or more subpicture tracks.