Lossless Intra Coding in HEVC with Integer-to-Integer DST

TL;DR

This paper introduces an innovative lossless intra coding method in HEVC using integer-to-integer transforms, including a novel approximation of the DST, achieving competitive compression results with minimal modifications to existing standards.

Contribution

It proposes a new lossless coding approach based on i2i transforms, including a novel i2i DST approximation, enhancing compression efficiency in HEVC.

Findings

Competitive compression results in HEVC with i2i transforms

The novel i2i DST approximation performs well in experiments

Minimal modifications needed for lossless coding in HEVC

Abstract

It is desirable to support efficient lossless coding within video coding standards, which are primarily designed for lossy coding, with as little modification as possible. A simple approach is to skip transform and quantization, and directly entropy code the prediction residual, but this is inefficient for compression. A more efficient and popular approach is to process the residual block with DPCM prior to entropy coding. This paper explores an alternative approach based on processing the residual block with integer-to-integer (i2i) transforms. I2i transforms map integers to integers, however, unlike the integer transforms used in HEVC for lossy coding, they do not increase the dynamic range at the output and can be used in lossless coding. We use both an i2i DCT from the literature and a novel i2i approximation of the DST. Experiments with the HEVC reference software show competitive results.