Lossless compression in HEVC with integer-to-integer transforms

Abstract

Many approaches have been proposed to support lossless coding within video coding standards that are primarily designed for lossy coding. The simplest approach is to just skip transform and quantization and directly entropy code the prediction residual, which is used in HEVC version 1. However, this simple approach is inefficient for compression. More efficient approaches include processing the residual with DPCM prior to entropy coding. This paper explores an alternative approach based on processing the residual with integer-tointeger (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. Experiments with the HEVC reference software show competitive results.

Lossless Image and Intra-Frame Compression With Integer-to-Integer DST

“…where m and n are integers representing the frequency and time index of the basis functions, respectively. When the first (m = 1) and most important basis function is plotted, one can see that, similar to the first basis function of the ODST-3 in Equation (10), it has smaller values at the beginning (i.e. closer to the prediction boundary) and larger values towards the end of the block, which implies that the EDST-3 may have good coding gain, in particular better than the conventionally used DCT, for block-based spatial prediction residuals.…”

“…Finally, Section VI concludes the paper. Note that some preliminary results of this work were presented in [10], [15]. II.…”

“…This paper focuses on lossless compression for intra coding. For lossless inter coding, some of our preliminary results are provided in [10]. In lossy intra coding, it is known that a hybrid separable 2D transform based on the odd type-3 discrete sine transform (ODST-3) and the DCT [11], [12] or simply a 2D ODST-3 [1] provides improved compression performance over the traditional 2D DCT at transform coding block-based spatial prediction residuals.…”