EXFO EXpert IPTV Test Tools (FTB-1 / 2 Pro) - Manual (Page 63)

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A.2.3.2 VQmon/HD Video Service Transmission Quality Metric - VSTQ
VQmon/HD produces a video services quality metric, VSTQ (Video Service Transmission
Quality), which is a codec-independent measure of the ability of the bearer channel to support
reliable video. This video service quality metric is expressed in the range of 0.0 to 50.0, as
defined in [14].
VSTQ can be calculated by a mapping function from Peak Signal-to-Noise Ratio PSNR
values as follows:
VSTQ = max(0, min(50, (PSNR - 12) * 1.8))
Of course, VQmon/HD uses a more sophisticated algorithm to calculate the resulting
VSTQ score, which takes time-varying distributions of network impairments and
recency into account.
Note: The VSTQ score that VQmon/HD’s API function produces actually ranges from 0
to 100. This value is scaled by 2 to get half-point accuracy for the score.