  Video streaming via TCP networks has become a popular and highly demanded
service, but its quality assessment in both objective and subjective terms has
not been properly addressed. In this paper, based on statistical analysis a
full analytic model of a no-reference objective metric, namely Pause Intensity,
for video quality assessment is presented. The model characterizes the video
playout buffer behavior in connection with the network performance (throughput)
and the video playout rate. This allows for instant quality measurement and
control without requiring a reference video. Pause intensity specifically
addresses the need for assessing the quality issue in terms of the continuity
in the playout of TCP streaming videos, which cannot be properly measured by
other objective metrics such as PSNR, SSIM and buffer underrun or pause
frequency. The performance of the analytical model is rigidly verified by
simulation results and subjective tests using a range of video clips. It is
demonstrated that pause intensity is closely correlated with viewer opinion
scores regardless of the vastly different composition of individual elements,
such as pause duration and pause frequency which jointly constitute this new
quality metric. It is also shown that the correlation performance of pause
intensity is consistent and content independent.
