A DCT domain frame-skipping transcoder

In video transcoding, pre-encoded frames may be dropped from incoming sequence to freely adjust the video to meet network and client requirements. When some of the reference frames are dropped, quantized DCT coefficients of residual signal of non-skipped frames become invalid as they may refer to the reference frame(s) which no longer exists in the transcoded bit-stream. So, it becomes necessary to re-compute the new set of quantized DCT coefficients with respect to past reference frame(s) that acts as reference in the transcoded bit-stream. The pixel-domain approach to this problem involve high computation and quality degradation due to double re-encoding. In this paper, we propose a method to compute the quantized DCT coefficients for non-skipped frames entirely in the DCT-domain. Experimental results are presented and compared.