Video quality metric for bit rate, control via joint adjustment of quantization and frame rate

The purpose of this study is to propose a quality metric of video encoded with variable frame rates and quantization parameters suitable for mobile video broadcasting applications. As a first step, experiments are conducted to assess the subjective quality of video sequences encoded with variable frame rates and quantization parameters. Resulting experimental data show that for the purpose of video rate control, optimization using the classical PSNR does not match up to that of subjective quality data. The second step bridges this gap between PSNR and subjective quality data by constructing a new quality metric that accounts for both encoding parameters (quantization and frame rate), and intrinsic video sequence characteristics (motion speed). The average correlation coefficient for five video sequences tested is as high as 0.93 with the proposed metric, in contrast with the PSNR's 0.70.