Video Bitstream DPB Signaling with Conditional SPS Flags
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Solution Overview
Problem
The signalling of syntax elements in the sequence parameter set for decoded picture buffer information in video coding is inefficient and inconsistent, leading to suboptimal compression ratios and picture quality.
Innovation Solution
A method and apparatus for encoding and decoding video bitstreams that efficiently signal syntax elements by determining the presence of decoded picture buffer parameters and syntax structures, allowing for reliable control of DPB syntax elements and improved coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If decoded picture buffer parameters syntax structure is always present in SPS, then DPB information can be reliably signaled, but bitstream size increases and coding efficiency decreases
Solution Approach 1:
The patent introduces dynamic flag-based control mechanisms (sps_ptl_dpb_hrd_params_present_flag, sps_sublayer_dpb_params_flag, dpb_parameters_present_flag) that allow the DPB parameters syntax structure to be conditionally present or absent in the bitstream. This dynamic approach enables the system to adapt the level of detail in DPB parameter signaling based on actual needs, improving coding efficiency while maintaining reliability when required.
Solution Approach 2:
The patent changes the state of DPB parameter inclusion from a fixed constant to a variable controlled by multiple syntax flags. By introducing conditional parameters that can switch between present and absent states based on flag values, the system optimizes the balance between reliability and coding efficiency for different video sequence requirements.
2Productivity
If multiple syntax flags are used to control DPB parameter presence, then coding efficiency improves, but device complexity increases
Solution Approach 1:
The patent segments the control of DPB parameter presence into multiple independent flag variables at different hierarchical levels (sps_ptl_dpb_hrd_params_present_flag for PTL level, sps_sublayer_dpb_params_flag for sublayer level, dpb_parameters_present_flag for DPB parameters level). This segmentation allows each flag to control specific aspects independently, making the complex control mechanism more manageable and enabling selective processing based on actual requirements.
Solution Approach 2:
The patent introduces intermediate syntax flags that act as mediators between the SPS structure and the actual DPB parameters. These flag variables serve as control intermediaries that determine whether subsequent DPB parameter syntax elements should be parsed and processed, simplifying the overall processing logic by providing clear conditional gates.
3Reliability
If DPB parameters are signaled for all temporal sublayers, then decoding reliability is improved, but bitstream redundancy increases
Solution Approach 1:
The patent applies local quality control by allowing different DPB parameter configurations for different temporal sublayers through the sps_sublayer_dpb_params_flag. This enables the system to provide detailed DPB parameters only for sublayers that require them, while using default or inherited parameters for other sublayers, thus eliminating unnecessary redundancy while maintaining decoding reliability where needed.
Solution Approach 2:
The patent implements partial action by signaling DPB parameters only for the subset of temporal sublayers that require explicit parameter specification. Rather than uniformly signaling parameters for all sublayers, the system applies DPB parameter syntax only where necessary, reducing bitstream size while maintaining sufficient decoding reliability.
Data Source
AI summary
Signalling of syntax elements in a sequence parameter set of a video bitstream is addressed. Particularly, it is provided a method of decoding a video bitstream wherein a sequence parameter set, SPS, is coded that contains syntax elements that apply to a video sequence, the method comprising obtaining a value of a first syntax element from the SPS used to specify whether a decoded picture buffer, DPB, parameters syntax structure is present in the SPS and obtaining a value of a second syntax element from the SPS, at least when determining that the value of the first syntax element specifies that the DPB parameters syntax structure is present in the SPS, used to specify the presence of a DPB syntax element in the DPB parameters syntax structure, wherein the DPB syntax element is applied to a temporal sublayer except for the highest temporal sublayer in the video sequence.