SPS Layer ID Constraint for Error-Free Sub-Bitstream Extraction
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Solution Overview
Problem
Video coding systems face errors during sub-bitstream extraction due to incorrect removal of the Sequence Parameter Set (SPS) when a Video Parameter Set (VPS) is removed, leading to incomplete decoding of layers.
Innovation Solution
Constrain the SPS to have a nuh_layer_id equal to the nuh_layer_id of the Coded Layer Video Sequence (CLVS) when inter-layer prediction is not used, and infer vps_independent_layer_flag to be one when sps_video_parameter_set_id is zero, ensuring the SPS is not mistakenly removed during sub-bitstream extraction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If sub-bitstream extraction removes the VPS to increase coding efficiency, then processor and memory resource usage is reduced, but the SPS may be mistakenly removed leading to decoding errors
Solution Approach 1:
The patent changes the nuh_parameter_id parameter of the SPS to match the nuh_layer_id of the CLVS when inter-layer prediction is not used. This parameter modification ensures that the SPS retains its layer identifier and is not mistakenly removed during sub-bitstream extraction, while still allowing the VPS to be removed for coding efficiency.
Solution Approach 2:
The patent introduces an intermediary constraint mechanism that mediates between the VPS removal for efficiency and the SPS retention for reliability. By constraining the SPS nuh_parameter_id to equal the CLVS nuh_layer_id under specific conditions, the system creates a protective intermediary layer that prevents erroneous removal of the SPS while allowing VPS removal.
2Reliability
If the SPS nuh_parameter_id is set equal to the CLVS nuh_layer_id, then the SPS is retained during sub-bitstream extraction, but this constraint must be carefully managed to avoid incorrect parameter assignment
Solution Approach 1:
The patent applies local quality by making the nuh_parameter_id constraint specific to certain conditions rather than universal. The constraint that SPS nuh_parameter_id equals CLVS nuh_layer_id is applied only when the layer does not use inter-layer prediction, allowing flexibility in other scenarios and reducing overall complexity.
Solution Approach 2:
The patent dynamically adjusts the nuh_parameter_id parameter based on the inter-layer prediction flag. When inter-layer prediction is not used, the parameter is changed to match the CLVS nuh_layer_id; otherwise, it maintains its original value, thereby managing complexity through conditional parameter assignment.
3Loss of substance
If sub-bitstream extraction is performed on simulcast layers, then the VPS can be removed to reduce data size, but this may cause references to the VPS to become invalid
Solution Approach 1:
The patent extracts only the necessary information for simulcast layer decoding by removing the VPS while preserving the SPS with the constrained nuh_parameter_id. This extraction process reduces data size while maintaining reference validity because the SPS self-contained layer identifier eliminates dependencies on the removed VPS.
Data Source
AI summary
A video coding mechanism is disclosed. The mechanism includes encoding a coded layer video sequence (CLVS) for a layer in a bitstream. A sequence parameter set (SPS) referred to by the CLVS is also encoded into the bitstream. The SPS is constrained to have a network abstraction layer (NAL) unit header layer identifier (nuh_layer_id) value equal to a nuh_layer_id value of the CLVS when the layer does not use inter-layer prediction. The bitstream is stored for communication toward a decoder.