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Time index (steps of 4s)
Figure 2. Video quality index dependency on the video content for various resolutions.
Suitability for drive testing scenarios: fine resolution and two quality indexes . The fine geographical/spatial resolution with the short measurement time window of drive test data characteristics enables pinpointing geographically with good accuracy where a network problem caused degradation of the video quality. To best suit these drive test data characteristics, which are crucial for troubleshooting and optimization, the VSQI model uses short video sessions (30-40sec) to keep the video buffer small and thus ensure small delays from the moment when a network problem occurs to the moment its impact affects the video quality. With the same scope of best suiting drive test data characteristics, the VSQI model is designed with two outputs: VSQIinstant and VSQIsession .
Meaningful network performance evaluation, troubleshooting and optimization require a video quality index, which exhibits variability with network errors and captures only the network’s impact. It should show consistent results, independent of the video content which can change the results according to its type, as described above. It is recommended though that the selection of the video content be made considering that stationary and less dense content is expected to provide higher scores while hiding possible existing network problems. Therefore, Infovista’s VSQI model applies normalization to the most sensitive video content in the mapping process of the input parameters to the perceived video quality (MOS). Consequently, VSQI output shows meaningful variability for detecting network problems, troubleshooting and optimization.
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