Constrained Layer-Wise Video Coding for Inter-Layer Prediction
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Solution Overview
Problem
In layer-wise video coding, particularly in Versatile Video Coding (VVC), the inter-layer prediction faces challenges when the chroma formats of different layers are different, leading to issues in generating chroma component predictors, as seen when a monochrome coded layer is referenced by a layer in 420 chroma format, causing problems in motion compensation.
Innovation Solution
Constraining the bitstream conformance by ensuring that the bit depth and chroma format values are the same or compatible between layers, allowing for consistent chroma format indexing and bit depth usage, and applying motion compensation using derived scaling ratios and sample positions based on chroma formats and bit depths to facilitate accurate prediction and interpolation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If inter-layer prediction is supported in VVC with different chroma formats between layers, then layer-wise video coding flexibility is improved, but chroma component predictor generation fails when chroma formats differ
Solution Approach 1:
The patent applies parameter changes by modifying the chroma format parameters (chroma_format_idc) to be consistent across layers. Specifically, it constrains that the chroma format of the current layer must match the chroma format of reference layers, ensuring that chroma component predictors can be properly generated during inter-layer prediction without format mismatch errors.
2Manufacturing precision
If bitstream conformance allows different bit depths between layers, then video quality range is improved, but motion compensation accuracy deteriorates due to bit depth mismatches
Solution Approach 1:
The patent applies parameter changes by constraining bit depth parameters (bit_depth_minus8) to be consistent between current and reference layers. This ensures that motion compensation operations maintain numerical precision and accuracy, as pixel value ranges and arithmetic operations remain compatible across layers during inter-layer prediction.
Data Source
AI summary
Method and apparatus of video coding using a multi-layer prediction mode, are disclosed. According to one method, a bitstream is generated at an encoder side or received at a decoder side, where the bitstream corresponds to coded data of current video data in a current layer. The bitstream complies with a bitstream conformance requirement corresponding both the bit depth values for the current layer and the reference layer being the same and the chroma format index values for the current layer and the reference layer being the same. The current video data in the current layer is then encoded or decoded by utilizing reference video data in the reference layer.