Effects of Temporal Jitter on Video Quality: Assessment Using Psychophysical Methods

The conventional synchronous model of digital video, in which video is reconstructed synchronously at the decoder on a frame-by-frame basis, assumes its transport is delayjitter-free. This assumption is inappropriate for modern integrated service packet networks such as the Internet for network delay jitter varies widely. Furthermore, multiframe buffering is not a viable solution in interactive applications such as video conferencing. We have proposed a “delay cognizant” model of video coding (DCVC) that segments an incoming video into two video flows with different delay attributes. The DCVC decoder operates in an asynchronous reconstruction mode that attempts to maintain image quality in the presence of network delay jitter. Our goal is to maximize the allowable delay of one flow relative to that of the other with minimal effect on image quality since an increase in the delay offset reflects more tolerance to transmission delay jitter. Subjective quality evaluations indicated for highly compressed sequences, differences in video quality of reconstructed sequences with large delay offsets as compared with zero delay offset are small. Moreover, in some cases asynchronously reconstructed video sequences look better than the zero delay case. DCVC is a promising solution to transport delay jitter in low-bandwidth video conferencing with minimal impact on video quality.