Luma-Chroma Phase Offset Filters for Scalable Video Resampling
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Solution Overview
Problem
Existing scalable video coding systems face inefficiencies in upsampling processes due to fixed phase offsets for luma and chroma components, which fail to accurately compensate for phase offsets introduced during downsampling, particularly in SHVC, leading to suboptimal encoding and decoding efficiency.
Innovation Solution
The proposed solution involves separate accounting for luma and chroma phase offsets during upsampling, using either fixed filters with adjustable phase offsets or adaptive filters, and signaling these offsets through syntax elements to ensure accurate reconstruction of full resolution video.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If fixed phase offsets are used for luma and chroma components during upsampling, then the upsampling process is simple and fast, but the accuracy of phase compensation is insufficient leading to suboptimal encoding and decoding efficiency
Solution Approach 1:
The patent segments the phase offset compensation process by separately accounting for luma and chroma phase offsets. Instead of using a single fixed phase offset for both components, the invention divides the compensation into two independent parts: one for luma (brightness) and one for chroma (color), allowing each to be optimized independently for better accuracy while maintaining implementation simplicity
Solution Approach 2:
The invention changes the parameter approach from fixed phase offsets to variable phase offsets that can be adjusted based on the specific downsampling ratio and component type. By signaling phase offset values through syntax elements and allowing them to vary according to the actual downsampling configuration, the system achieves more accurate compensation without significantly increasing complexity
2Measurement precision
If separate accounting for luma and chroma phase offsets is implemented, then phase offset compensation accuracy is improved, but the device complexity increases due to additional syntax elements and processing
Solution Approach 1:
The patent applies preliminary action by pre-defining the relationship between downsampling ratios and phase offset values. The encoder determines the appropriate phase offsets based on the configured downsampling ratio and signals these through syntax elements, allowing the decoder to directly apply the predetermined offsets without complex real-time calculations, thus reducing overall system complexity while maintaining accuracy
Solution Approach 2:
The invention creates a universal phase offset compensation mechanism that works across different downsampling ratios and component types through a unified syntax element structure. The same basic framework handles both luma and chroma components, and can adapt to various downsampling configurations, reducing the need for separate specialized processing paths and thereby limiting complexity growth
Data Source
AI summary
A sampling filter process is provided for scalable video coding. The process provides for re-sampling using video data obtained from an encoder or decoder process of a base layer (BL) in a multi-layer system using adaptive phase shifting to improve quality in Scalable High efficiency Video Coding (SHVC). In order to compensate for phase offsets introduced by downsampling an appropriate phase offset adjustment is made for upsampling in SHVC with an appropriate offset included for proper luma/chroma color space positions. In one approach the luma/chroma phase offset is specified and a filter is selected to apply the appropriate phase change.