EXFO EXpert IPTV Test Tools (FTB-200v2) - Manual (Page 65)

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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.
A.2.3.3 Degradation Factors
To facilitate troubleshooting, VQmon/HD has the ability to obtain a breakdown of
factors contributing to quality degradation. VQmon/HD reports the severity of quality
degradation (on a scale of 0‐10, with 0 indicating no degradation and 10 indicating the
most severe level of degradation) attributable to each of the following factors:
 Packet loss
 Audio‐video sync
 Codec quantization
 GOP length
 Codec bandwidth restriction
 Frame resolution
 Packet discards due to jitter
 Frame rate
 (One‐way) delay
 Recency
*Note:
Information in this document is proprietary to Telchemy, Incorporated and was
published with its permission.