Video Bitstream Picture Output Ordering for VVC Conformance
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Solution Overview
Problem
The latest designs of POC, GDR, EOS, and still picture profiles in VVC have issues such as incorrect POC derivation, improper use of GDR, discontinuity in multi-layer bitstreams, and absence of output pictures, which affect decoding and bitstream conformance.
Innovation Solution
Implementing specific constraints on syntax elements like ph_poc_msb_cycle_present_flag, ensuring synchronized decoding and output orders, requiring CLVSS pictures after EOS NAL units, and ensuring at least one picture is output, to address these issues.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If syntax elements are constrained to ensure correct POC derivation, then decoding accuracy is improved, but bitstream complexity increases
Solution Approach 1:
The patent applies parameter changes by constraining the relationship between syntax elements (ph_poc_msb_cycle_present_flag, ph_pic_order_cnt_lsb, ph_poc_msb_cycle_val) to ensure correct POC derivation. Specific constraints are imposed on these parameters to prevent incorrect POC values while maintaining efficient bitstream representation.
2Stability of the object's composition
If GDR pictures are properly constrained in bitstream, then decoding continuity is improved, but encoding complexity increases
Solution Approach 1:
The patent applies preliminary action by establishing constraints on GDR picture usage before decoding occurs. The encoder pre-determines which pictures can be GDR pictures based on bitstream conformance rules, ensuring decoding continuity is maintained without requiring complex runtime decisions during decoding.
3Reliability
If CLVSS pictures are required after EOS NAL units, then bitstream conformance is improved, but encoding flexibility decreases
Solution Approach 1:
The patent applies parameter changes by imposing specific constraints on picture types following EOS NAL units. The syntax element constraints ensure that CLVSS pictures are properly positioned in the bitstream, maintaining conformance while allowing encoders flexibility in other areas of the video sequence.
4Reliability
If output picture constraints are enforced, then decoded picture availability is improved, but decoding complexity increases
Solution Approach 1:
The patent applies feedback by using syntax elements in the bitstream that provide information about picture output requirements. The decoder uses these feedback signals (such as ph_pic_output_flag and related constraints) to determine which pictures should be output, ensuring reliability without requiring complex external verification.
Data Source
AI summary
Methods, systems and devices for picture output ordering constraints in video bitstreams are described. An example method of video processing includes performing a conversion between a video including one or more pictures and a bitstream of the video according to a rule, wherein the rule specifies that the bitstream includes at least a first picture that is output, wherein the first picture is in an output layer, wherein the first picture includes a syntax element equal to one, and wherein the syntax element affects a decoded picture output and a removal process associated with a hypothetical reference decoder (HRD).