Subpicture Track Encapsulation for VVC APS Collision Avoidance
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Solution Overview
Problem
The encapsulation of subpicture bitstreams in media files faces challenges due to the risk of APS identifier collisions, where different subpicture bitstreams with the same type and identifier but different content can lead to decoding issues in merged bitstreams, particularly in VVC specifications.
Innovation Solution
A method is devised to encapsulate subpicture bitstreams by generating a base track that references multiple subpicture tracks, creating a spatial arrangement, and providing information describing APS, including maximum buffer size, identifiers, and rewriting requirements, to avoid identifier collisions and ensure correct decoding.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple subpicture bitstreams are merged into a single media file, then the media file can contain multiple spatial regions or layers, but APS identifier collisions occur causing decoding issues
Solution Approach 1:
The patent segments the APS identifier space by introducing separate identifier ranges for different subpicture bitstreams. Each subpicture bitstream is assigned a unique identifier range, preventing collisions when multiple subpicture bitstreams are merged into a single media file while maintaining the ability to decode each segment correctly
Solution Approach 2:
The patent introduces an intermediary mapping mechanism that translates APS identifiers from different subpicture bitstreams into a unified identifier space. This mediator layer resolves identifier collisions by remapping conflicting identifiers to unique values while preserving the original semantic meaning
2Productivity
If APS identifiers are reused across different subpicture bitstreams, then the identifier space is efficiently utilized, but decoding ambiguity arises
Solution Approach 1:
The patent adds an additional dimension to APS identification by introducing subpicture-specific identifier ranges. Instead of using a flat one-dimensional identifier space that causes collisions, the system creates a multi-dimensional identifier structure where the same identifier value can exist in different subpicture contexts without ambiguity
3Reliability
If identifier rewriting is performed to avoid collisions, then decoding accuracy is maintained, but processing complexity increases
Solution Approach 1:
The patent performs identifier range assignment and collision detection in advance during the media file creation process. By preliminarily organizing identifiers into non-overlapping ranges for each subpicture bitstream, the system avoids the need for complex real-time rewriting operations during playback, reducing processing complexity while maintaining accuracy
Data Source
AI summary
The present invention concerns a method of encapsulating subpicture bitstreams in at least one media file, the subpicture bitstreams corresponding to encoded media data of a subpicture corresponding to a rectangular region of video data, the method comprising: obtaining the plurality of subpicture bitstreams; encapsulating each subpicture bitstream in a subpicture track; generating at least one base track referencing at least two subpicture tracks and forming a spatial arrangement of the at least two subpicture tracks; generating information describing APS referenced by samples of the at least two subpicture tracks; encapsulating the subpicture tracks, the at least one base track and the information describing APS in the at least one media file.