Multi-rate encoding of a video sequence in the DCT domain

In today's streaming servers, video sequences are offered to users at different fixed bit rates. This paper presents an efficient approach for simultaneous encoding of a video sequence at multiple bit rates. In this encoder, motion estimation is performed only once for the reference stream. We also take the DCT out of the encoding loop so that it is only computed once per frame. As a result, no iDCT has to be computed at the encoder. However, motion compensation is performed in the DCT domain, and drift error can be introduced adaptively to reduce the computational cost of the DCT-domain motion compensation. Results show that significant computational reduction can be achieved with less than 0.3 dB loss in PSNR when compared to independently encoding the video sequence at multiple rates.