Optical Flow Prediction Refinement for Low-Complexity Motion Compensation
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Solution Overview
Problem
Existing video coding technologies, such as VVC, face inefficiencies in motion compensation due to limitations in block-based motion refinement methods, particularly with bi-directional optical flow (BDOF) and prediction refinement with optical flow (PROF) for affine mode, leading to suboptimal coding efficiency and hardware implementation challenges.
Innovation Solution
Implement bit-depth control mechanisms for bi-directional optical flow (BDOF) and decoder-side motion vector refinement (DMVR) through control flags and presence flags in sequence and picture headers, enabling precise motion vector refinement and harmonizing the designs of BDOF and PROF to facilitate hardware implementation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If block-based motion refinement methods (BDOF, PROF) are used to improve motion compensation precision, then manufacturing precision is improved, but device complexity increases
Solution Approach 1:
The patent applies parameter changes by introducing bit-depth control mechanisms that dynamically adjust the precision parameters of motion vectors and optical flow calculations. By modifying the bit-depth parameter, the system can optimize between precision and computational complexity, allowing high precision where needed while reducing complexity in other regions, thus resolving the contradiction between manufacturing precision and device complexity.
Solution Approach 2:
The patent implements dynamic control through multiple flags (sps_bdof_enabled_flag, sps_prof_enabled_flag, sps_dmvr_enabled_flag) that enable or disable different refinement methods based on content characteristics. This dynamic adaptation allows the system to apply complex algorithms only when necessary, reducing overall device complexity while maintaining high precision where required by the video content.
2Adaptability or versatility
If multiple control flags and presence flags are transmitted to enable precise control of BDOF, PROF, and DMVR, then adaptability is improved, but loss of information increases
Solution Approach 1:
The patent segments the control mechanism into multiple hierarchical levels: sequence-level flags (sps_bdof_enabled_flag, sps_prof_enabled_flag, sps_dmvr_enabled_flag) and picture-level flags (picture_disable_bdof_flag, picture_disable_prof_flag, picture_disable_dmvr_flag). This segmentation allows fine-grained control adaptability at different granularities while managing bit rate overhead efficiently by only transmitting flags when necessary.
Solution Approach 2:
The patent uses presence flags (sp s_bdof_presence_flag, sps_prof_presence_flag, sps_dmvr_presence_flag) that are only transmitted when the corresponding control flags are true. This partial action approach minimizes information loss by avoiding transmission of redundant flag data, thereby reducing bit rate overhead while maintaining full adaptability when needed.
Data Source
AI summary
A method for video encoding, a comuting device, and a non-transitory computer readable storage medium are provided. The method includes transmitting, by an encoder, a first control flag in a sequence parameter set (SPS), a second control flag in the SPS, and a third control flag in the SPS; transmitting, by the encoder, a first presence flag in the SPS when the first control flag is true, a second presence flag in the SPS when the second control flag is true and a third presence flag in the SPS when the third control flag is true; transmitting, by the encoder, a first/second/third picture control flag in a picture header of each picture that refers to the SPS when the first/second/third presence flag in the SPS is true.