An analysis of subjective quality in low bit rate video

A subjective quality evaluation was performed to quantify viewer responses to various visual defects that appear in low bit rate video, both at full and reduced frame rates. The stimuli were eight video sequences compressed by three encoders operating at five bit rate/frame rate combinations. The sequences covered a broad range of typical streaming video content. Viewers continuously registered their responses to the stimuli as per the SSCQE method of ITU-R Recommendation BT.500-8. Data from 19 viewers was collected. An analysis of particularly disturbing artifacts is performed. The effects of changes in frame rate at a fixed bitrate on perceived quality are studied, demonstrating a preference for lower frame rates. A comparison of PSNR to the perceived quality ratings is made, revealing several notable trends