VVC Sub-Bitstream Extraction with Precise NAL and SEI Rules
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Solution Overview
Problem
The existing sub-bitstream extraction process in VVC has issues such as incorrect specification of tIdTarget range, improper handling of AUD NAL units, incomplete removal of SEI messages, and inconsistencies in handling scalable-nested SEI messages, leading to non-conforming bitstreams.
Innovation Solution
Specify tIdTarget within the correct range, treat AUD NAL units similarly to other NAL units, refine SEI message removal criteria, and ensure proper handling of scalable-nested SEI messages to generate conforming sub-bitstreams.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing sub-bitstream extraction process is used, then the extraction can be performed quickly, but the generated bitstream is non-conforming due to incorrect specification of tIdTarget range, improper handling of AUD NAL units, incomplete removal of SEI messages, and inconsistencies in handling scalable-nested SEI messages
Solution Approach 1:
The patent segments the sub-bitstream extraction process into distinct operational steps: (1) determining the target OLS and tIdTarget value, (2) identifying and removing SEI NAL units based on specific criteria, (3) handling AUD NAL units separately, and (4) processing scalable-nested SEI messages. This segmentation allows each aspect to be handled with precise rules, ensuring bitstream conformity while maintaining clear process organization.
Solution Approach 2:
The patent specifies precise parameter ranges and values for the extraction process, including defining tIdTarget as being in the range of 0 to vps_max_sublayers_minus1, and establishing specific conditions for SEI message removal based on payload types and layer identifiers. These parameter specifications ensure that the extraction process generates conforming bitstreams by adhering to standardized constraints.
2Loss of information
If all SEI NAL units are removed regardless of conditions, then the extraction process is simple, but important supplemental enhancement information is lost
Solution Approach 1:
The patent applies different removal rules to different types of SEI NAL units based on their local characteristics. SEI messages with payload types indicating they apply to removed pictures are removed, while other SEI messages are preserved. The process also distinguishes between scalable-nested SEI messages and non-scalable-nested SEI messages, applying appropriate handling to each. This localized quality approach ensures that only necessary SEI information is removed while preserving important supplemental enhancement data.
3Manufacturing precision
If the tIdTarget range is not properly specified, then the extraction process is flexible, but the generated sub-bitstream may be non-conforming
Solution Approach 1:
The patent precisely defines the tIdTarget parameter range as 0 to vps_max_sublayers_minus1, where vps_max_sublayers_minus1 is obtained from the video parameter set. This precise parameter specification ensures that the extracted sub-bitstream conforms to the VVC standard while maintaining adaptability through the use of the vps_max_sublayers_minus1 variable, which can take different values based on the specific bitstream configuration.
Data Source
AI summary
Examples of video encoding methods and apparatus and video decoding methods and apparatus are described. An example method of video processing includes performing a conversion between a video and a bitstream of the video. The bitstream includes network abstraction layer (NAL) units for multiple video layers according to a rule. The rule defines a sub-bitstream extraction process by which NAL units are removed from the bitstream to generate an output bitstream, and specifies to remove all supplemental enhancement information (SEI) NAL units that contain a non-scalable-nested SEI message with a particular payload type, responsive to a list of NAL unit header layer identifier values in an output layer set (OLS) with a target OLS index not including all values of NAL unit header layer identifiers in all video coding layer (VCL) NAL units in the bitstream that is input to the sub-bitstream extraction process.