Coded Video Stream Access Signaling for Stable Multilayer Decoding
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Solution Overview
Problem
Existing video coding technologies struggle with managing random access points and decoding processes in coded video streams with multiple layers, particularly in scenarios involving unavailable reference pictures due to random access or unintended picture loss, leading to decoder crashes or unintended behavior.
Innovation Solution
The method involves signaling flags to indicate the presence of intra random access point (IRAP) and gradual decoding refresh (GDR) pictures, along with network abstraction layer (NAL) unit types, to manage decoding processes and generate default pixel values for unavailable pictures, ensuring proper decoding and recovery in multi-layered video streams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If random access points are indicated in high-level syntax structures, then random access capability is improved, but decoder complexity increases due to multiple flag alignments and picture management
Solution Approach 1:
The patent applies preliminary action by indicating random access point information (IRAP and GDR picture flags) in advance within high-level syntax structures before actual decoding occurs. This allows the decoder to pre-identify and prepare for random access points, enabling efficient seeking and recovery operations without requiring complex runtime analysis of picture types.
Solution Approach 2:
The patent introduces intermediary elements (ra_pb_applied_flag, ra_tb_applied_flag, and related picture flags) that mediate between the random access requirement and the decoding process. These flags act as intermediaries that carry random access point information through the bitstream hierarchy, allowing the decoder to manage multiple picture types (IRAP, GDR, non-GDR) systematically without direct complex interactions.
2Adaptability or versatility
If multiple picture types (IRAP and GDR) are supported, then decoding flexibility is improved, but reliability decreases due to potential decoder crashes from unavailable reference pictures
Solution Approach 1:
The patent applies preliminary anti-action by proactively managing reference picture availability before decoding operations that could cause failures. The decoder uses the indicated random access point information to pre-identify unavailable reference pictures and applies compensation measures (such as using alternative reference pictures or generating default pictures) before the decoding process encounters errors, thus preventing decoder crashes.
Solution Approach 2:
The patent implements beforehand cushioning by maintaining additional reference picture buffers and alternative decoding paths in advance. When random access occurs or pictures are lost, these pre-prepared cushioning resources allow the decoder to recover gracefully without crashing, providing a safety margin that absorbs the impact of unavailable reference pictures.
3Speed
If random access information is signaled in high-level syntax, then access efficiency is improved, but bitstream overhead increases
Solution Approach 1:
The patent extracts random access point information (IRAP and GDR picture identification) from the detailed picture parameter syntax and places it in high-level syntax structures. This extraction allows random access functionality to be indicated with minimal overhead at the high level, while avoiding the need to repeat this information in every picture's detailed parameters, thus reducing overall bitstream overhead.
Solution Approach 2:
The patent makes the high-level random access point indicators universal by designing them to serve multiple functions: identifying IRAP pictures, indicating GDR picture boundaries, and providing recovery point information. This multi-functionality allows a single set of flags and syntax elements to handle various random access scenarios without requiring separate signaling mechanisms for each case, thereby minimizing bitstream overhead.
Data Source
AI summary
Systems and methods for decoding a coded video stream are provided. A method includes receiving a coded video stream that includes an access unit, including a picture; signaling a first flag that indicates whether the access unit includes either or neither one from among an intra random access point (IRAP) picture and a gradual decoding refresh (GDR) picture; signaling a second flag that indicates whether the picture is the IRAP picture; and decoding the picture, as a current picture, based on the signaling of the first flag and the second flag, wherein a value of the first flag and a value of the second flag are aligned.