Adaptive Loop Filtering by Temporal Layer for Lower Decoder Complexity
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Solution Overview
Problem
Existing video coding systems face challenges in efficiently managing computational complexity in adaptive loop filter (ALF) procedures, particularly when dealing with frames at different temporal layers in a coding scheme.
Innovation Solution
The system adaptively selects an ALF procedure based on the temporal layer of a frame, using a less computationally complex procedure for higher temporal layers and a more complex procedure for the lowest temporal layer, and selectively skips block classification and gradient calculations to reduce complexity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a more computationally complex ALF procedure is applied to all frames, then video quality is improved, but computational complexity increases
Solution Approach 1:
The patent applies dynamic selection of ALF procedures based on temporal layer identification. Different ALF procedures (first, second, third) are selectively applied to frames depending on their temporal layer, allowing the system to adapt computational complexity to the specific requirements of each frame type rather than using a fixed complex procedure for all frames.
Solution Approach 2:
The patent applies different ALF procedures to different temporal layers of frames. Higher temporal layers receive simpler ALF procedures while lower temporal layers receive more complex procedures, ensuring that each part of the video stream receives the appropriate level of processing quality based on its specific characteristics and importance.
2Measurement precision
If block classification is performed on all pixels, then classification accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent performs block classification on a subset of pixels rather than all pixels in a block. This partial action approach maintains sufficient classification accuracy for the application while significantly reducing the computational complexity associated with processing every pixel in each block.
3Manufacturing precision
If gradient calculations are performed for all pixels, then filtering accuracy is improved, but computational complexity increases
Solution Approach 1:
The patent calculates gradients only for a subset of pixels rather than all pixels in each block. This partial calculation approach maintains sufficient filtering accuracy while reducing the computational burden of gradient calculations across the entire image.
Solution Approach 2:
The patent dynamically adjusts the extent of gradient calculations based on the temporal layer of the frame. For higher temporal layers, gradient calculations are performed on fewer pixels, while for lower temporal layers, more comprehensive gradient calculations are performed, optimizing the balance between accuracy and complexity for each frame type.
Data Source
AI summary
Systems, methods and instrumentalities are disclosed for adaptively selecting an adaptive loop filter (ALF) procedure for a frame based on which temporal layer the frame is in. ALF procedures may vary in computational complexity. One or more frames including the current frame may be in a temporal layer of a coding scheme. The decoder may determine the current frame's temporal layer level within the coding scheme. The decoder may select an ALF procedure based on the current frame's temporal layer level. If the current frame's temporal layer level is higher within the coding scheme than some other temporal layer levels, an ALF procedure that is less computationally complex may be selected for the current frame. Then the decoder may perform the selected ALF procedure on the current frame.