HEVC VPS Extension Level Parameter Flexibility
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Solution Overview
Problem
The existing High Efficiency Video Coding (HEVC) profile_tier_level syntax structure lacks flexibility in supporting variance of Level parameters separately from Profile/Tier parameters, limiting its applicability in scalable, multi-view, and 3D video coding scenarios.
Innovation Solution
The introduction of a new 'LevelPresentFlag' within the profile_tier_level syntax structure allows for the separate selection and presence indication of Level parameters, enabling more flexible parameter selection and inference mechanisms for profile and tier information in vps_extension syntax structures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the profile_tier_level syntax structure uses a unified structure for Profile/Tier and Level parameters, then the syntax structure is simple, but it lacks flexibility in supporting separate variance of Level parameters from Profile/Tier parameters
Solution Approach 1:
The profile_tier_level syntax structure is segmented by introducing separate flags: profile_present_flag for Profile/Tier parameters and level_present_flag for Level parameters. This allows independent control and selection of each parameter type, enabling flexible configuration where only necessary parameters are present in the bitstream, thus resolving the contradiction between flexibility and complexity.
Solution Approach 2:
The syntax structure becomes dynamic through the introduction of conditional presence flags. The profile_present_flag and level_present_flag allow the syntax structure to adapt its content based on what is actually needed for each layer or operating point, making the structure flexible rather than static, thereby achieving versatility without excessive complexity.
2Productivity
If Level parameters are always present in the profile_tier_level syntax structure, then decoder compatibility is ensured, but bitstream efficiency decreases due to redundant information
Solution Approach 1:
The level_present_flag extracts the Level parameters from the mandatory presence requirement, allowing them to be conditionally included only when necessary. This separates the Level parameters from the always-present Profile/Tier parameters, enabling bitstream efficiency improvement without compromising decoder compatibility, as decoders can rely on the flag to know when Level information is provided.
Solution Approach 2:
The introduction of the level_present_flag changes the parameter presence from a fixed state to a variable state. This allows the Level parameters to be dynamically included or excluded based on actual needs, improving bitstream efficiency by eliminating redundant information while maintaining compatibility through the flag mechanism that informs decoders about parameter availability.
3Adaptability or versatility
If profile information is inferred from reference layers, then syntax structure simplicity is maintained, but flexibility in profile selection is reduced
Solution Approach 1:
The profile_present_flag enables a preliminary action mechanism where the encoder can proactively indicate whether profile information should be inferred from reference layers or explicitly provided. This allows decoders to prepare appropriately in advance, knowing whether to perform inference or use explicit values, thereby maintaining flexibility in profile selection without adding complex inference mechanisms.
Data Source
AI summary
The profile_tier_level syntax structure of a High Efficiency Video Coding (HEVC) syntax structure is updated to provide more flexibility for use in the vps_extension( ) syntax structure for use in each layer or operating point. A new flag ‘LevelPresentFlag’ is added in profile_tier_level syntax structure to support the variance of Level parameters separately from the Profile/Tier Parameter. The update to the profile_tier_level syntax structure provides flexibility in selecting profile_tier and level parameters for HEVC selections in scalable video coding, multi-view coding and 3D video coding areas.