Perceptual quality and objective quality measurements of compressed videos

This paper firstly presents a study of video quality for H.264 compressed videos compared to MPEG-4 (simple profile) from a perceptual point of view. Traditionally, peak signal-to-noise ratio (PSNR) has been used to represent the quality of a compressed video sequence. However, PSNR has been found to correlate poorly with subjective quality ratings, particularly at much lower bitrates and low frame rates. Thus, an alternative that has been commonly used is to perform subjective test where a large number of human subjects are used to gauge the quality of a video. However, this process is not only time-consuming but also tedious and expensive to perform. Hence, this paper further proposes an objective video quality measurement method to automatically measure the perceptual quality of a stream of video images. The proposed method has been tested on multimedia videos, consisting of CIF and QCIF video sequences compressed at various bitrates (24–384 kbps) and frame rates (7.5–30 fps) using the H.264 and MPEG-4 video codecs and it is shown to give significantly better correlations to the human perception than PSNR and the video structural similarity method.