Dct Domain Hdtv To Sdtv Video Codec Key Algorithm

Compared with the traditional pixel domain video transcoding, the transcoding from HDTV to SDTV in the DCT domain, not only avoids the DCT and IDCT transforms, but also avoids motion estimation, the most computation costing process, by making full use of the macroblock motion vector information from the input HDTV stream to construct the motion vector for the according SDTV macroblocks. It's helpful to achieve the HDTV to SDTV video transcoding in the real time.This dissertation presents the research on the fast motion compensation algorithm with the shared macroblock information in the dct domain and rate control algorithm with dct coefficients. The fast motion compensation can save 44% computation compared to the traditional motion compensation in the dct domain. Compared with the TM5 method, the rate control algorithm can not only increase the encoding images PSNR, but also solve the scene change problem.The key transcoding algorithms are achieved by the C language, and we optimize the most computation costing transcoding programs with the SSE2 assembly language, which is based on the Intel Pentium 4 CPU and has the SIMD function. At last, we achieve the quick video transcoding from HDTV to SDTV in the dct domain on the PC.