Trapezoidal block split using orthogonal C2 transforms for HEVC video coding

We present an extension for HEVC intra-frame coding with trapezoidal splits and orthogonal transforms. A block can be split into two 180-degrees rotationally-symmetric (C2) trapezoidal parts, each coded separately using standard DCT implementation. We also introduce part-to-part prediction from a diagonal edge. The optimal trapezoidal split of a quad tree block is selected in a rate-distortion sense. We achieved 0.8% reduction in BD-rate over HEVC in standard test conditions for intra coding.