The difference between perceived video quality and objective video quality

We select 93 video sequences encoded/decoded by Microsoft MPEG-4 software to classify them into six different content characteristics by the cluster analysis and the discriminant analysis in this study. We compare the peak signal noise ratio (PSNR) of objective video quality evaluation with the mean opinion score of subjective quality evaluation to understand their difference by varying different bit rate. We find that the acceptable satisfaction of user perceived quality for different motion and texture characteristics is significantly different in varying the bit rates. For the low motion and simple texture characteristic (Type 1) and the low motion and complex texture characteristic (Type 4), when the bit rate is 2,000 kbps, the tolerable discarded ratio is allowed to 44% and 49%, and the PSNR is 41.7 dB and 41.0 dB, subjects could perceive the acceptable satisfaction of video quality. For the middle motion and simple texture characteristic (Type 2) and the high motion and simple texture characteristic (Type 3), when the bit rate needs around 3,000 kbps, the tolerable discarded ratio must be controlled below 12% and 34%, and the PSNR is 45.2 dB and 41.7 dB, subjects could perceive the acceptable satisfaction of video quality. For the middle motion and complex texture characteristic (Type 5) and the high motion and complex texture characteristic (Type 6), when the bit rate is 6,000 kbps, the tolerable discarded ratio is allowed to 14%, and the PSNR is 43.2 dB and 42.9 dB, subjects could perceive the acceptable satisfaction of video quality.