Integer Modified Sine-Cosine Transforms Type VII. A construction Method and Separable Directional Adaptive Transforms for Intra Prediction with 8 × 8 Chroma Blocks in Image/Video Coding

Abstract

A matrix method for constructing a modified order-8 integer sine-cosine transform type VII is proposed. Based on the method, two order-8 integer modified sine-cosine transforms type VII are constructed and algorithms for fast computing of these transforms are developed, which require only integer operations. These algorithms are of low multiplicative complexity, which is 7 and 10.5 times less, and they require 23.3 and 44.2% less additional operations than the well-known algorithm of the discrete sine transform type VII. These transforms have higher coding gain performance for quality and compression ratio compared to the well-known sine transforms. Algorithms for fast computing of 2D separate directional integer cosine and modified sine-cosine type VII adaptive transforms for intra prediction with 8 × 8 chroma blocks are developed. These algorithms have low multiplicative complexity, which is 6.6 and 16.5 times less than that of the well-known algorithms.