Video Decoding Motion Vector Prediction with Candidate Offset Vectors
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Solution Overview
Problem
Existing video coding technologies face challenges in efficiently predicting motion vectors (MVs) for video decoding, particularly in scenarios where rounding errors occur during MV calculation, leading to suboptimal compression ratios and increased data requirements.
Innovation Solution
A method for video decoding that involves selecting a base vector from a candidate list, determining an offset vector based on offset information, and reconstructing samples using an intra block copy (IBC) mode, with biased offset directions and variable length codewords for improved MV prediction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If motion vector prediction is performed using conventional methods, then compression is achieved, but rounding errors occur during MV calculation leading to suboptimal compression ratios
Solution Approach 1:
The patent applies preliminary action by pre-defining a set of candidate offset vectors before the actual MV prediction process. These candidate offsets are prepared in advance based on statistical analysis of natural video characteristics, allowing the decoder to quickly select the most appropriate offset without performing complex real-time calculations, thereby avoiding rounding errors while maintaining high compression ratios
Solution Approach 2:
The patent changes the parameter representation by introducing a discrete set of candidate offset vectors instead of using continuous offset values. This parameter discretization transforms the MV prediction process into a selection problem from predefined candidates, which eliminates rounding errors and improves both accuracy and compression efficiency
2Measurement precision
If more data is transmitted for MV information, then MV prediction accuracy improves, but data requirements increase
Solution Approach 1:
The patent applies local quality by transmitting only the index of the selected candidate offset vector rather than the complete offset information. Since the candidate set is pre-defined and shared between encoder and decoder, only a small number of bits are needed to indicate which candidate to use, significantly reducing data requirements while maintaining high MV prediction accuracy
Solution Approach 2:
The patent uses copying by having both encoder and decoder maintain identical sets of candidate offset vectors. The encoder selects and transmits only the index of the best matching candidate, and the decoder reproduces the exact same candidate from its local copy of the candidate set, ensuring accurate reconstruction with minimal data transmission
Data Source
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AI summary
Aspects of the disclosure provide a method and an apparatus including processing circuitry for video decoding. The processing circuitry decodes prediction information of a current block in a current picture from a coded video bitstream. The prediction information indicates a prediction mode for the current block being an inter prediction mode or an intra block copy (IBC) mode. The processing circuitry selects a base vector from a candidate list including a block vector candidate used in the IBC mode and determines an offset vector based on offset information that includes directions and sizes for constructing offset vectors. The processing circuitry determines a vector of the current block based on the base vector and the offset vector. The vector is a block vector when the prediction mode is the IBC mode and the vector is a motion vector when the prediction mode is the inter prediction mode.