Lossless Image and Intra-frame Compression with Integer-to-Integer DST

TL;DR

This paper introduces novel integer-to-integer (i2i) transforms based on ODST-3 for lossless intra-frame compression, achieving better efficiency than traditional DPCM methods with minimal complexity increase.

Contribution

It develops new i2i approximations of ODST-3 for lossless intra coding, improving compression efficiency over existing DPCM-based methods.

Findings

Achieves an average 2.7% improvement in lossless intra-frame compression.

Maintains similar computational complexity to existing methods.

Demonstrates effectiveness within HEVC reference software.

Abstract

Video coding standards are primarily designed for efficient lossy compression, but it is also desirable to support efficient lossless compression within video coding standards using small modifications to the lossy coding architecture. A simple approach is to skip transform and quantization, and simply entropy code the prediction residual. However, this approach is inefficient at compression. A more efficient and popular approach is to skip transform and quantization but also process the residual block with DPCM, along the horizontal or vertical direction, prior to entropy coding. This paper explores an alternative approach based on processing the residual block with integer-to-integer (i2i) transforms. I2i transforms can map integer pixels to integer transform coefficients without increasing the dynamic range and can be used for lossless compression. We focus on lossless intra coding and develop novel i2i approximations of the odd type-3 DST (ODST-3). Experimental results with the HEVC reference software show that the developed i2i approximations of the ODST-3 improve lossless intra-frame compression efficiency with respect to HEVC version 2, which uses the popular DPCM method, by an average 2.7% without a significant effect on computational complexity.