Configurable NAL Code Point Mapping for Video Stream Merging
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Solution Overview
Problem
Existing video coding technologies face inefficiencies in merging multiple coded video bitstreams due to constraints on Network Abstract Layer (NAL) unit types, particularly when combining Random Access Point (RAP) and non-RAP NAL units, leading to bitrate costs and detection issues.
Innovation Solution
A mechanism for mapping NAL unit types using a configurable NAL and slice code point system, allowing flexible rewriting of NAL unit types in parameter sets, enabling efficient merging of video coding units and reducing the need for IDR pictures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple coded video bitstreams are merged using existing video coding technologies, then video stream integration is achieved, but bitrate costs increase and detection issues occur due to constraints on NAL unit types
Solution Approach 1:
The patent introduces a mapping mechanism that transforms NAL unit types by changing their parameter representation. A parameter set contains mapping information that reinterprets NAL unit type code points, allowing RAP and non-RAP units to be merged without increasing bitrate. The decoder uses this mapping to correctly interpret merged stream NAL units regardless of their original type
Solution Approach 2:
The patent introduces a parameter set as an intermediary layer between the encoder and decoder. This parameter set contains mapping information that mediates the interpretation of NAL unit types during stream merging. The mapping mechanism acts as a translator that allows different NAL unit types to coexist in merged streams without causing detection issues or requiring additional bitrate
2Reliability
If NAL unit types are constrained to maintain proper decoding, then decoding accuracy is ensured, but merging efficiency of multiple video streams deteriorates
Solution Approach 1:
The patent makes the NAL unit type interpretation dynamic through the mapping mechanism. Instead of fixed type constraints, the system dynamically adjusts type interpretation based on the mapping information in the parameter set. This allows the decoder to adaptively interpret NAL unit types in merged streams, maintaining decoding accuracy while enabling flexible stream merging
Solution Approach 2:
The parameter set with mapping information serves a universal function across different NAL unit types. The same mapping mechanism handles both RAP and non-RAP units, allowing a single decoding path to process merged streams with diverse NAL unit types. This multi-functional approach maintains reliability while improving merging efficiency
3Reliability
If IDR pictures are used frequently to ensure random access, then access reliability is improved, but coding efficiency and bitrate utilization worsen
Solution Approach 1:
The patent changes the parameter interpretation of NAL unit types through mapping, allowing non-RAP units to be treated as accessible in merged streams. This eliminates the need for frequent IDR pictures to ensure random access, as the mapping mechanism provides the necessary access reliability through parameter reinterpretation rather than through frequent refresh frames
Data Source
AI summary
A video decoding apparatus includes processing circuitry configured to perform operations comprising: receiving, from a video data stream, a sequence parameter set (SPS); parsing, from the SPS, an extra slice header bit map; mapping one or more bits in the extra slice header bit map to one or more flags that indicate presence or non-presence corresponding to a syntax element in a slice header; determining a number of extra slice header bits based on an amount of the one or more flags that indicate presence; and parsing, from the video data stream, the syntax element in the slice header based on the determined number of extra slice header bits.