Gilge's “Shape-Adapted” DCT

The proposed method has been tested also with the higher-complexity “Shape-Adapted” DCT (Gilge, 1989), which is known as the best shape-adaptive transform for arbitrary supports in terms of approximation of a SA-KLT. This transform is constructed by orthogonalization of a set of generating functions (e.g. basis) on an arbitrarily-shaped sub-support. This orthogonalization is not a trivial task because generators are usually linearly-dependent.

By replacing the low-complexity SA-DCT with Gilge's “Shape-Adapted” DCT, one typically obtains some improvement. However, this improvement is negligible (about 0.1dB) and nearly invisible.