Quantitative perceptual comparison of variable bit rate over constant bit rate encoding scheme for MPEG-4 video

Between the two main schemes of digital video coding, VBR encoding scheme is generally considered as better in terms of efficiency and encoding quality in comparison to CBR, because it retains the same quantization parameters for the whole encoding procedure (unconstrained VBR), without altering them according to a specific adaptive rate algorithm. Towards this generally accepted statement, this paper presents a quantitative comparison to the perceptual efficiency of VBR over CBR for Moving Picture Expert Group – 4 (MPEG-4) ASP CIF and QCIF encoding sequences, showing that the VBR does not out-perform significantly the corresponding CBR encoding quality, since the deduced perceptual advantage/ratio of VBR over CBR for CIF is approximately 4-5% and constant for all the encoding bit rates greater than 200 kbps, while for the QCIF-case the relative ratio drops to approximately 2.5%.