Perceptual video quality assessment on a mobile platform considering both spatial resolution and quantization artifacts

In this paper, we investigated the impact of spatial resolution and quantization on the perceptual quality of a compressed video coded from the SVC reference software - JSVM. Two subjective quality tests have been carried out on the TI Zoom2 mobile development platform (MDP). 5 different spatial resolutions (i.e., from QCIF to 4CIF) and 4 different quantization levels (i.e., QP 22, 28, 36, 44) are chosen to create the processed video sequences (PVS) from 7 different video sources. First test focuses on the effect of spatial resolution at fixed QP 22, while second test explores the impact of both spatial resolution and quantization artifacts. Videos coded at different spatial resolutions are displayed at the full screen size of the mobile platform. We report the test results in terms of how MOS reduces as the spatial resolution decreases at constant QP, and how MOS reduces as QP increases under the same spatial resolution. We found that the dropping rate of the MOS vs. spatial resolution increases as QP increases and the dropping rate of the MOS vs. QP increases as spatial resolution reduces. In addition, the dropping rate against spatial resolution is faster when the video is changing in a lower motion speed; while the dropping rate against QP is faster when the video has less texture details. Also, the dropping rate of MOS against spatial resolution can be captured by a one-parameter falling exponential function in most of cases.