Colour space transforms for improved video compression

The Version 1 of the latest video coding standard High Efficiency Video Coding (HEVC) supports 4:2:0 colour sampling and colour representation that includes a luminance and two chrominance colour bands. To enable efficient coding of content with 4:4:4 sampling format and RGB colour space some improvements to the coding pipeline are needed. This paper investigates methods for converting RGB colour space into a luminance and two chrominance colour space suitable for HEVC encoding. Four colour transform domains, namely, YCbCr, YCoCg, Karhunen-Loève Transform (KLT) and 3-point Pseudo Discrete Cosine Transform (P-DCT), are investigated for converting RGB into a colour space usable in HEVC range extension test model. One of the proposed approximations of KLT transform matrices results in overall highest BD-rate savings and BD-PSNR improvements.