HEVC Bitstream Random Access via NAL Unit Header Rewriting
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Solution Overview
Problem
Current MMT standards are limited in supporting high efficiency video coding (HEVC) bitstreams with SAP types 2 and 3, as they rely on Network Abstraction Layer (NAL) unit type information for random access, which is not efficiently handled by existing systems.
Innovation Solution
The method involves identifying and processing HEVC bitstreams for MMT to support random access without relying on NAL Unit Type fields, by setting the HandleCraAsBlaFlag and rewriting NAL unit headers to handle Clean Random Access (CRA) and Broken Link Access (BLA) pictures appropriately, allowing for efficient decoding and presentation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If MMT standards rely on NAL Unit Type information for random access, then existing systems can process bitstreams, but support for HEVC bitstreams with SAP types 2 and 3 is limited
Solution Approach 1:
The patent extracts and removes the dependency on NAL Unit Type fields by introducing a new random access mechanism that operates independently of these fields. The system identifies random access points through alternative means (such as picture timing information and decoder state management) rather than relying on NAL unit type indicators, thereby enabling support for HEVC bitstreams with SAP types 2 and 3 while reducing structural complexity.
Solution Approach 2:
The patent changes the parameter used for identifying random access points from NAL Unit Type fields to picture timing information and decoder state flags. By modifying how random access is detected and handled (using parameters like `picture_timing_info`, `decoded_picture_buffer`, and `random_access_flag`), the system achieves compatibility with HEVC bitstreams while maintaining processing efficiency.
2Productivity
If NAL Unit Type fields are used for identifying random access points, then processing is straightforward, but efficient decoding and presentation of HEVC bitstreams is not achieved
Solution Approach 1:
The patent introduces intermediary structures and flags (such as `random_access_flag`, `picture_timing_info`, and `decoded_picture缓冲`) that mediate between the raw bitstream and the decoding process. These intermediaries enable efficient random access by providing structured information about picture timing and decoder state, allowing the system to efficiently present HEVC bitstreams without requiring complex processing of NAL unit type fields.
3Reliability
If existing MMT processing methods are used, then current bitstream formats are supported, but seamless random access of HEVC bitstreams cannot be achieved
Solution Approach 1:
The patent creates a universal random access mechanism that can handle both existing bitstream formats and new HEVC bitstreams with SAP types 2 and 3. By implementing a flexible picture timing information structure and decoder state management system, the same processing framework can accommodate multiple bitstream types without requiring separate handling mechanisms, thereby maintaining compatibility while enabling extended functionality.
Data Source
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AI summary
A method and apparatus for randomly accessing high efficiency video coding (HEVC) bitstream for moving picture experts group (MPEG) media transport (MMT). The method includes receiving a plurality of packets for a video in decoding order. The method also includes determining a packet marked to begin processing the video, removing packets of leading pictures in the marked packet from the memory, and processing the packets remaining in the memory.