Adaptive Transform Selection for Video Encoding
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Solution Overview
Problem
Existing video encoding and decoding methods use fixed transforms that do not adapt to varying video content and coding parameters, leading to suboptimal compression performance.
Innovation Solution
Adaptive transform selection during encoding and decoding, where the transform set is updated in real-time based on previously encoded pictures, using techniques like singular value decomposition to match the video sequence and coding parameters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a fixed transform is used for all blocks, then the device complexity is reduced, but the compression performance deteriorates due to inability to adapt to varying video content
Solution Approach 1:
The patent applies dynamics by transitioning from a fixed transform to an adaptive transform selection mechanism. The encoder dynamically selects transforms from a predefined set based on block characteristics and video content, while the decoder dynamically receives and applies the same selected transforms. This dynamic adaptation resolves the contradiction by enabling content-aware compression without requiring complex real-time transform design.
Solution Approach 2:
The patent changes the transform parameter selection based on block size and content characteristics. Instead of using a single fixed transform, the system selects from multiple predefined transforms (e.g., DCT-8, DCT-4, DCT-16) depending on the block dimensions and visual content properties. This parameter variation allows optimization of compression performance for different video scenarios.
2Productivity
If multiple transforms are selected adaptively, then the compression performance is improved, but the device complexity increases due to transform selection and signaling requirements
Solution Approach 1:
The patent segments the transform selection process into two independent parts: encoder-side transform selection based on block characteristics, and decoder-side transform application based on received indices. This segmentation allows each side to operate with simplified logic while achieving adaptive compression. The transform indices are segmented and transmitted efficiently in the bitstream.
Solution Approach 2:
The patent implements feedback through the signaling of transform indices in the bitstream. The encoder selects transforms and signals their indices to the decoder, creating a feedback loop where the decoder receives and applies the same transform selection. This feedback mechanism ensures synchronization between encoder and decoder while maintaining relatively simple device architecture.
3Adaptability or versatility
If transforms are updated in real-time, then the adaptability to video content is improved, but the processing time increases
Solution Approach 1:
The patent applies preliminary action by pre-defining a set of candidate transforms before encoding begins. Instead of creating transforms in real-time, the system prepares a pool of predefined transforms (e.g., various DCT variants) and selects from this pre-prepared set during encoding. This preliminary preparation significantly reduces the processing time required during actual video encoding while maintaining high adaptability.
Data Source
AI summary
Methods and apparatus are provided for adaptive transform selection for video encoding and decoding. An apparatus includes a video encoder for encoding at least a block in a picture using a transform. The transform used to encode the block is selected from a plurality of transforms. The plurality of transforms is adaptively updated during the encoding of the picture.