EOS NAL Layer Signaling for VVC Bitstream Sequencing
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Solution Overview
Problem
The existing designs for handling End of Sequence (EOS) Network Abstraction Layer (NAL) units in the Versatile Video Coding (VVC) standard have issues that cause confusion and interoperability problems, including constraints that violate temporal scalability and allow for incorrect associations between picture units (PUs) and NAL units, leading to inconsistencies in bitstream handling.
Innovation Solution
The proposed solutions include modifying the definitions and constraints related to EOS NAL units in the VVC standard to allow for different layer identifiers, multiple EOS NAL units per PU, and specifying that the next PU after an EOS NAL unit must be an Intra Random Access Point (IRAP) or Gradual Decoding Refresh (GDR) PU, ensuring correct sequencing and layer adherence.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the existing VVC standard constraints for EOS NAL units are applied, then sequence termination is defined, but temporal scalability is violated and interoperability problems occur
Solution Approach 1:
The patent introduces dynamic layer identifier assignment for EOS NAL units, allowing the layer_id to vary based on the specific layer being terminated rather than being fixed. This enables the bitstream to adapt to different temporal scalability configurations while maintaining proper sequence termination, resolving the conflict between reliability and adaptability.
Solution Approach 2:
The patent modifies the layer_id parameter of EOS NAL units to match the layer being terminated, and changes the interpretation of EOS NAL units from sequence-level to layer-level termination markers. This parameter change enables proper handling of temporal scalability while maintaining interoperability through consistent decoding behavior.
2Device complexity
If EOS NAL units are restricted to specific positions in the bitstream, then parsing is simplified, but flexibility in bitstream structure is reduced
Solution Approach 1:
The patent makes EOS NAL units universal termination markers that can appear in multiple positions within the bitstream structure, serving both as sequence termination markers and layer termination markers. This multi-functionality allows flexible bitstream organization while maintaining simple parsing through consistent EOS NAL unit handling.
Solution Approach 2:
The patent segments the bitstream into independent layers, each with its own EOS NAL unit for termination. This segmentation allows each layer to be parsed independently with clear termination points, simplifying the overall parsing complexity while enabling flexible multi-layer bitstream structures.
3Manufacturing precision
If layer identifiers in EOS NAL units are constrained to specific values, then standard compliance is easier to verify, but temporal scalability is violated
Solution Approach 1:
The patent changes the layer_id parameter of EOS NAL units from fixed values to values that dynamically match the layer being terminated. This allows precise verification through the equality check between EOS NAL unit layer_id and the target layer's layer_id, while fully supporting temporal scalability configurations.
Solution Approach 2:
The patent implements a feedback mechanism where the layer_id in the EOS NAL unit is set based on the layer information from the associated VCL NAL unit. This feedback ensures standard compliance verification is straightforward while maintaining adaptability to different temporal scalability arrangements.
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 conforms to a format rule. The bitstream includes one or more layers including one or more picture units (PUs). The format rule specifies that, responsive to a first PU in a layer of the bitstream following an end of sequence network abstraction layer (EOS NAL) unit in the layer in a decoding order, a variable of the first PU is set to a particular value, wherein the variable indicates whether the first PU is a coded layer video sequence start (CLVSS) PU.