Adaptive Coefficient Scan Ordering for Lower Bitrate Video Coding
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Solution Overview
Problem
Existing block transform-based codecs face inefficiencies due to pre-determined coefficient scan patterns that are not optimal for all image regions, particularly in textured and linear feature areas, and are influenced by lapped transforms and DCAC prediction efficiency.
Innovation Solution
An adaptive coefficient scan ordering technique that adjusts the scan order based on local image statistics, using arrays to track non-zero coefficient incidence and swapping indices for more efficient entropy encoding, without additional signaling or latency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If pre-determined coefficient scan patterns are used, then device complexity is reduced and ease of operation is improved, but compression efficiency deteriorates in textured and linear feature regions
Solution Approach 1:
The patent implements dynamic scan order selection by maintaining multiple scan order tables and adaptively switching between them based on local image characteristics. The scan order is no longer fixed but changes dynamically according to the statistical properties of different image regions, resolving the contradiction between operational simplicity and compression efficiency.
Solution Approach 2:
The patent applies different scan orders to different regions of the image based on local statistical characteristics. By analyzing local variance and coefficient distribution in textured versus non-textured regions, the system selects appropriate scan orders for each region, achieving locally optimized compression without requiring complex global analysis.
2Productivity
If adaptive scan order adjustment is implemented, then compression efficiency is improved, but device complexity and computational requirements increase
Solution Approach 1:
The patent implements a simplified adaptive approach by monitoring only key statistical features (such as variance and non-zero coefficient counts) rather than performing exhaustive analysis of all coefficients. This partial adaptation achieves sufficient compression improvement while avoiding the computational burden of complete statistical characterization.
Solution Approach 2:
The patent pre-computes and stores multiple scan order tables that can be directly selected based on local image characteristics. By preparing these tables in advance, the system avoids complex real-time optimization calculations during encoding, reducing computational complexity while maintaining adaptive benefits.
3Productivity
If fixed scan tables are used, then computational efficiency is maintained and latency is minimal, but bitrate reduction is limited
Solution Approach 1:
The patent introduces dynamic selection among a limited set of pre-defined scan orders rather than computing optimal scan orders in real-time. This approach maintains computational efficiency by avoiding complex calculations while achieving bitrate reduction through adaptive matching of scan patterns to local image characteristics.
Data Source
AI summary
A digital media codec adaptively re-arranges a coefficient scan order of transform coefficients in accordance with the local statistics of the digital media, so that the coefficients can be encoded more efficiently using entropy encoding. The adaptive scan ordering is applied causally at encoding and decoding to avoid explicitly signaling the scan order to the decoder in the compressed digital media stream. For computational efficiency, the adaptive scan order re-arranges the scan order by applying a conditional exchange operation on adjacently ordered coefficient locations via a single traversal of the scan order per update of the statistical analysis.