A Fast Arbitrary Down-Sizing Algorithm for Video Transcoding

We propose a fast algorithm to down-size video frames, by arbitrary factor, directly in DCT domain. The existing methods treat each 8×8 block as a fundamental unit, therefore, involve high cost of reconstructing down-sized frames. We demonstrate that a basic operation in reconstructing 16×16 macroblock, as a whole, can be represented as multiplication by fixed matrices and the computations can be greatly simplified through decomposition of DCT/IDCT matrix operations. Experimental results using cascaded DCT domain transcoder (CDDT) show substantial reduction in cost of reconstructing down-sized frames at quality similar to the existing methods.