Exfo EXpert IPTV Test Tools (FTB-1 / 2 Pro) Uživatelský manuál stáhnout pdf (Strana 49)

A.1.1.2 Impact of Packet Loss on Specific Video Codecs

As shown in Figure 2-3, a simple non-robust video stream can be severely degraded with even

low levels of packet loss due to the error propagation effects described above. Peak Signal-to-

Noise Ratio (PSNR) is an objective measurement of video service quality comparing the

maximum power of the video signal to the power of corrupting noise affecting the signal.

Generally, a PSNR of under 20dB is regarded as unwatchable, and this level is reached for

MPEG video with a loss rate under 1 percent.

Figure 2-3.

Estimated PSNR

for Three

Common Codecs

1 2 ... 44 45 46 47 48 49 50 51 52 53 54 ... 81 82

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Exfo EXpert IPTV Test Tools (FTB-1 / 2 Pro) Uživatelský manuál Strana 49