Hybrid domain processing of multi-dimensional transformed data

摘要

A one-dimensional (1D) Inverse Discrete Cosine Transform (IDCT) is applied to an input two-dimensional (2D) transform block along the axis to be modified. Since the one-dimensional IDCT is not performed on the other axis, each block is left in a one-dimensional transform space (called hybrid space). For a shift (merge), the appropriate "m" elements are picked up from one block and the "8-m" elements are picked up from the other block and are used as input to the one-dimensional forward DCT (FDCT) along that same axis. For two-dimensional shifts or merges, the results of the first one-dimensional IDCT and FDCT can be stored with extra precision to be used as input to a second one-dimensional IDCT and FDCT along the other axis. The execution time worst case conditions are approximately constant for all shift/merger amounts. Taking advantage of fast paths can improve the execution times for typical blocks.