  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-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. Experiments with the HEVC reference software show competitive results.
