Quality metric for video sequences with temporal scalability

For the purpose of temporally scalable video coding and multi-dimensional bit rate control, we conducted experiments of subjective quality assessment for video sequences encoding with variable frame rates and quantization parameters. The experimental results show that the correlation between the PSNR and the subjective quality becomes very low when the two coding parameters vary simultaneously. Then, we propose a new quality metric that takes into account the quantization errors, frame rates, and motion speeds. This metric has a higher correlation with the subjective quality. The average correlation coefficient for five video sequences is as high as 0.93, whereas that of the PSNR is only 0.70.