Video Quality Assessment: Some Remarks on Selected Objective Metrics

Abstract

The paper presents selected objective video quality assessment metrics. The authors discuss the usefulness of the PSNR, NQI and SSIM metrics in the face of the disparity of the results which sometimes occur during tests. The measurements were performed in the lossless environment for different videos and using modern VP9 and AV1 codecs with different compression ratios. Based on the high correlation between the results of the objective and subjective quality assessment the PSNR and SSIM metrics were chosen as the objective metrics that well describe the quality of the tested videos. One of the main contributions of the paper is an indication of high usefulness of the presented metrics as tools that may support creation of proper encoding ladders for specific videos. Such ladders define sets of configurations (i.a. data rates and resolutions) for display on a range of end user devices over a range of connection speeds. The tests have confirmed that AV1 codec allows to achieve the same video quality with generating up to 40% smaller file size. However, a several dozens larger processing time that was observed in the case of AV1 codec, indicates that currently it may not be used for live streaming, but only for ‘on demand’ services.