With the development of the broadband IP networks, video distribution, streaming, and communication services
over networks are rapidly becoming common. To provide these services appropriately, we must design, monitor,
and manage their quality based on subjective video quality. Therefore, we need an objective quality assessment
method that enables video quality to be evaluated from video characteristics easily and quickly. We have
already proposed an objective video quality assessment method for freeze distortion in network video services
by considering the perceptual characteristics of short freeze distortion. In this previous method, we derived the
objective video quality under the assumption that all freeze lengths in the video are constant. However, it was
impossible to derive objective video quality when arbitrary freeze lengths occur because of network degradation in
real services. We propose an objective video quality assessment method for arbitrary freeze lengths by extending
the previous method and confirm that it can estimate subjective video quality with good accuracy for real
applications. The correlation coefficient between subjective and objective quality is 0.94.
With the development of the broadband network, video communications such as videophone, video distribution, and IPTV services are beginning to become common. In order to provide these services appropriately, we must manage them based on subjective video quality, in addition to designing a network system based on it. Currently, subjective quality assessment is the main method used to quantify video quality. However, it is time-consuming and expensive. Therefore, we need an objective quality assessment technology that can estimate video quality from video characteristics effectively. Video degradation can be categorized into two types: spatial and temporal. Objective quality assessment methods for spatial degradation have been studied extensively, but methods for temporal degradation have hardly been examined even though it occurs frequently due to network degradation and has a large impact on subjective quality. In this paper, we propose an objective quality assessment method for temporal degradation. Our approach is to aggregate multiple freeze distortions into an equivalent freeze distortion and then derive the objective video quality from the equivalent freeze distortion. Specifically, our method considers the total length of all freeze distortions in a video sequence as the length of the equivalent single freeze distortion. In addition, we propose a method using the perceptual characteristics of short freeze distortions. We verified that our method can estimate the objective video quality well within the deviation of subjective video quality.