User's Manual Part 2

Tech-X Flex User Guide - Firmware v06.50 Tech-X Flex

(NG2)

6-46

Intro

Overview

Wi-Fi

Ethernet

System

IP/Video

MoCA

Specs

• The structure and length of GOPs (MPEG Groups of Pictures), especially with regards to the varied

effects of packet loss on different frame types.

• The bit rate and frame size (or resolution) used at the encoder, as smaller rates and lower resolutions

can degrade the quality of the image even if transport is flawless.

• The impact of recency. Recency is the trend of human viewers to judge audio/video quality to be

lower immediately following a disturbance to the signal, and the subsequent trend for that perception

to improve gradually if time passes with no further disturbance.

• Packet loss distribution. Bursty packet loss events in which consecutive packets are dropped have a

different effect on perceived audio/video quality than packet loss events in which single packets are

dropped and the time (or “distance”) between the single loss events is significant.

• Loss of synchronization between the audio and video signals.

While it does not measure signal-to-noise directly, the analysis does use codec and packet loss/discard

information to calculate an estimated peak signal/noise ratio (EPSNR). The EPSNR is then used as a

key input for quality score calculations.

About MOS and R-factor calculations

MOS (mean opinion score) is a numerical system used to grade the subjective perceptual quality of a

multimedia (audio, video, or both) user experience. Originally based on ITU-T recommendations for the

evaluation of voice quality, it uses a scale of 1 - 5 to indicate user experience with the following typical

benchmarks:

MOS scoring is frequently produced by software algorithms that monitor multimedia streams and attempt

to “emulate” a subjective user experience. Such software is intended to produce results that are similar to

MOS scores that would be recorded by actual human participants consuming and evaluating the media.

Score Quality Human perception of degradation

5 Excellent Imperceptible. No degradation of quality can be detected

by a human subject.

4 Good Perceptible. Degradation can detected, but does not

adversely impact the user experience.

3 Fair Slightly annoying

2 Poor Annoying

1 Bad Very annoying or no data stream present

Preliminary issue - Limited distribution only!