Adaptive Loop Filter Control for Video Coding Error Resilience
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Solution Overview
Problem
Existing video coding methods, such as those in the HEVC standard, face limitations in achieving a balance between coding efficiency and error resilience, particularly in adapting to changing network conditions and varying error propagation across slices within a picture, leading to suboptimal performance in error resilience and coding efficiency.
Innovation Solution
A method for coding and decoding at the picture and slice layers that dynamically selects Constrained Loop Filter (CLF) and Constrained Intra Prediction (CIP) control modes based on network transmission state and video content characteristics, allowing for adaptive control of CLF and CIP flag bits in picture and slice parameter sets to optimize error resilience and coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the loop filter is not allowed to cross slice boundaries (conservative strategy), then error resilience performance is improved, but coding efficiency deteriorates
Solution Approach 1:
The patent applies dynamics by making the loop filter boundary crossing control adaptive rather than static. The flag bit loop_filter_across_slice_flag is dynamically set based on real-time network transmission state feedback, allowing the system to switch between conservative (flag=0) and aggressive (flag=1) strategies according to current channel conditions, thus resolving the contradiction between error resilience and coding efficiency
Solution Approach 2:
The patent changes the parameter loop_filter_across_slice_flag from a fixed conservative value to a dynamically adjustable parameter based on network conditions. By monitoring network transmission state (packet loss rate, bit error rate) and adapting the flag value accordingly, the system optimizes the tradeoff between error resilience and coding efficiency for different transmission scenarios
2Reliability
If IDR picture is inserted to reinitialize SPS and change parameter settings, then error resilience performance is improved, but coding bit rate significantly increases
Solution Approach 1:
The patent extracts the parameter reinitialization function from the IDR picture mechanism. Instead of inserting full IDR pictures to reset SPS parameters, the system selectively updates only the necessary flag bits (loop_filter_across_slice_flag, constrained_intra_pred_flag) in the parameter sets, achieving parameter reconfiguration without the heavy bit rate penalty of complete intra refresh
Solution Approach 2:
The patent applies partial action by performing selective parameter updates rather than complete reinitialization. Only the specific loop filter and intra prediction control flags are modified based on network conditions, avoiding the excessive bit rate increase that would result from inserting full IDR pictures and reencoding all subsequent frames
3Adaptability or versatility
If PPS is used to control coding process, then control flexibility is improved, but separate control of different slices deteriorates
Solution Approach 1:
The patent segments the control mechanism by introducing slice-layer parameter sets (slice_header) that contain separate loop_filter_across_slice_flag and constrained_intra_pred_flag for each slice. This segmentation allows independent control of error resilience and coding parameters for different slices within the same picture, enabling differentiated strategies for slices with varying error susceptibility
4Device complexity
If uniform coding control is applied to all slices, then system complexity is reduced, but optimization for different error propagation characteristics deteriorates
Solution Approach 1:
The patent applies local quality by allowing different coding control parameters (loop_solve, constrained_solve) to be set independently for different slices based on their specific characteristics. Slices with high error propagation risk can use conservative settings (flag=0), while slices with low risk can use aggressive settings (flag=1), optimizing error resilience performance without uniformly increasing system complexity
Data Source
AI summary
Disclosed are methods for coding and decoding at picture layer and slice layer, and corresponding coder and decoder. The method comprises: coder selecting, according to network transmission state and video characteristic, different constrained loop filter (CLF) and/or constrained intra-prediction (CIP) control modes for one of the following three objects: 1: different video sequences; 2: pictures in different periods in the same video sequence; 3: different slices in the same picture; according to the selected CLF and/or CIP control mode, coding CLF and/or CIP control flag bits in picture layer parameter set and slice layer parameter set; and a decoder parsing slice layer bitstream containing header information, picture layer parameter set and/or slice layer parameter set, and according to the obtained CLF and/or CIP control flag bits, decoding picture and slice by using the corresponding CLF and/or CIP control mode. Through the present invention, a desirable tradeoff can be achieved between coding efficiency and error resilience performance.