Video Encoding with LCU Partitioning and Delta QP Control
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Solution Overview
Problem
Current video coding standards, such as H.264/AVC, face challenges with rate control and visual quality when using larger block sizes due to reduced granularity in quantization parameter (QP) adjustment, which affects coding efficiency and visual quality performance.
Innovation Solution
Implementing block-based video coding with larger block sizes (e.g., LCUs) that allow for multiple quantization parameters per block, partitioning LCUs into coding units (CUs) with varying sizes, and signaling delta QPs to maintain spatial granularity and improve rate control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If larger block sizes (LCUs) are used in video coding, then coding efficiency is improved, but rate control precision and visual quality deteriorate due to reduced quantization parameter adjustment granularity
Solution Approach 1:
The patent divides a large LCU (e.g., 64×64 pixels) into multiple smaller coding units (CUs) of varying sizes (e.g., 32×32, 16×16, 8×8 pixels). Each CU can have its own quantization parameter, enabling fine-grained rate control while maintaining the efficiency benefits of large block processing. This segmentation resolves the contradiction by allowing both large-block coding efficiency and small-block rate control precision.
Solution Approach 2:
The patent applies different quantization parameters to different coding units within the same LCU based on local image characteristics. Regions with high visual importance or complex content receive finer quantization (smaller QP), while less important regions use coarser quantization (larger QP). This local differentiation maintains visual quality where needed while achieving overall rate control, resolving the contradiction between coding efficiency and rate control precision.
2Loss of substance
If larger block sizes are used, then compression ratio is improved, but visual quality performance deteriorates due to reduced quantization granularity
Solution Approach 1:
By segmenting LCUs into multiple CUs with different sizes and applying different QP values, the patent enables selective preservation of visual detail in important regions while achieving higher overall compression. This resolves the contradiction by allowing high compression ratio globally while maintaining visual quality locally where needed.
Solution Approach 2:
The patent applies different quantization strengths to different regions based on their visual importance. Critical regions (e.g., edges, textures, motion areas) use finer quantization to preserve visual quality, while less critical regions use coarser quantization to maximize compression. This local quality approach resolves the contradiction between compression ratio and visual quality.
3Measurement precision
If multiple quantization parameters per block are implemented, then rate control precision is improved, but device complexity increases
Solution Approach 1:
The patent segments LCUs into CUs and applies different QP values, which does increase complexity but manages it through systematic rules for CU partitioning and QP derivation. The segmentation enables precise rate control while keeping the increased complexity manageable through structured approaches.
Solution Approach 2:
The patent derives QP values for different CUs by modifying a base QP value through systematic parameter changes based on CU size, position, and image characteristics. This approach to parameter management achieves precise rate control while avoiding the need for completely independent QP optimization for each CU, thereby managing encoding complexity.
4Measurement precision
If delta QP signaling is implemented for each coding unit, then spatial granularity is maintained, but bit rate overhead increases
Solution Approach 1:
The patent signals delta QP values for different CUs to achieve local quality differentiation and maintain spatial granularity in rate control. By using delta encoding (difference from a reference QP), the patent reduces the bit rate overhead compared to signaling absolute QP values for each CU, while still maintaining the ability to apply different quantization parameters locally.
Data Source
AI summary
A method is provided that includes receiving a coded largest coding unit in a video decoder, wherein the coded largest coding unit includes a coded coding unit structure and a plurality of coded quantization parameters, and decoding the coded largest coding unit based on the coded coding unit structure and the plurality of coded quantization parameters.