Abstract:

The real-time transcoding from MPEG-2 to MPEG-4, the discrete cosine transform (DCT) domain data of intra frame(I-frame) decoded in part by MPEG-2 decoder could not be directly used in re-quantization of MPEG-4. A quick compensation method based on DCT domain is proposed, in which the calculation time of six DCTs and six inverse DCTs are saved in each macroblock for implementing DCT and inverse DCT are not needed. Experimental results show that the transcoding time for I frame is saved by 65.05% and the peak signal-to-noise ratio (PSNR) error is in 0.001dB compared with the pixel domain compensation method.

Key words: MPEG-2, MPEG-4, transcoding, discrete cosine transform domain, requantization