Transform and Entropy Coding in AV2

2026-01-06

AI Summary

This work addresses the AV2 video coding standard by significantly enhancing compression efficiency and subjective visual quality while maintaining low encoder and decoder complexity. The proposed approach introduces a suite of innovative tools—including data-driven implicit secondary transform (IST), trellis-coded quantization (TCQ), adaptive transform selection (ATC), probability-adapted rate adjustment (PARA), intra reference frame coding (FSC), context modeling (CCTX), and phase-aware signaling (PH)—to enable extended transform partitioning and highly efficient, coefficient-dependent signaling strategies. Experimental results demonstrate that the proposed scheme achieves state-of-the-art video quality at substantially reduced bitrates, making it well-suited for a wide range of practical applications.

Technology Category

• Computer Vision: Video Understanding & Activity Analysis
• Cognitive Modeling & Cognitive Systems: Neural Spike Coding
• Machine Learning: Matrix & Tensor Methods

Application Category

• Systems and Infrastructure for Web, Mobile and WoT: Applied ML and AI for Web-based mobile applications
• Search and Retrieval-Augmented AI: Vertical and domain-specific search
• Security and Privacy: Large-scale security measurements

Abstract

AV2 is the successor to the AV1 video coding standard developed by the Alliance for Open Media (AOMedia). Its primary objective is to deliver substantial compression gains and subjective quality improvements while maintaining low-complexity encoder and decoder operations. This paper describes the transform, quantization and entropy coding design in AV2, including redesigned transform kernels and data-driven transforms, expanded transform partitioning, and a mode&coefficient dependent transform signaling. AV2 introduces several new coding tools including Intra/Inter Secondary Transforms (IST), Trellis Coded Quantization (TCQ), Adaptive Transform Coding (ATC), Probability Adaptation Rate Adjustment (PARA), Forward Skip Coding (FSC), Cross Chroma Component Transforms (CCTX), Parity Hiding (PH) tools and improved lossless coding. These advances enable AV2 to deliver the highest quality video experience for video applications at a significantly reduced bitrate.

Problem

• video compression
• compression efficiency
• subjective quality
• low-complexity coding
• next-generation video coding

Innovation

• Transform Coding
• Entropy Coding
• Adaptive Transform Coding
• Trellis Coded Quantization
• Cross Chroma Component Transforms