Towards understanding user tolerance to network latency in zoomable video streaming

Abstract

We conducted a user study with 35 participants viewing 5 video clips to understand user tolerance to network latency when zooming and panning in zoomable video streams. With zooming or panning, unseen spatial regions in a frame are revealed and momentarily in an unknown state until data arrive from the server. To handle such unknown state, two common concealment schemes are used, namely Black scheme and Low-Res scheme. Black scheme renders the newly revealed region as black pixels, while Low-Res covers the unknown part with data from a low resolution video stream, which is additionally streamed by the server. In the context of these schemes, our study based on the simulation of delays shows that users are more tolerable to delay in Low-Res scheme. Up to 94% of participants can tolerate 1 second delay and 80% can tolerate up to a delay of 2 seconds in Low-Res scheme, while only 77% of participants can tolerate 1 second delay in Black scheme. The tolerable delay in zoomable video streaming is higher than thresholds found in some high interactive multimedia applications. Copyright 2011 ACM.