DETEWE OpenCom 130 User Manual page 105

Voice over IP (VoIP)
■
G.729A (Level 2): Reduction to approximately 8 kilobit/s.
■
G.723.1 6.3 (Level 3): Reduction to 6.3 kilobit/s.
■
G.723.1 5.3 (Level 3): Reduction to 5.3 kilobit/s.
Unfavourable packet length selection may reduce voice quality. The duration of
the recording and not the data packet's byte count is relevant in making this
selection:
■
Duration <= 30 ms: optimal transmission
■
Duration 40 - 60 ms: one quality-level depreciation
■
Duration > 60 ms: two quality-levels depreciation
The achievable voice quality also depends on the packet propagation delay and
the packet loss between the terminals involved. These parameters can be deter-
mined using the "ping" program.
Packet Propagation Delay and Packet Loss
Value
Propagation delay
< 50 ms
Propagation delay
50-100 ms
Propagation delay
100-150 ms
Propagation delay
150-200 ms
Propagation delay
200-300 ms
Propagation delay
> 300 ms
Note: Measurements made with "ping" are round-trip pro-
pagation delays. Divide the maximum value displayed by
two.
Quality Level
Optimal
0.5 level
depreciation
1 level
depreciation
2 level deprecia-
tion
3 level deprecia-
tion
4 level deprecia-
tion
Value
Loss < 1 %
Loss 1-2 %
Loss 2-3 %
Loss 3-4 %
Loss 4-6 %
Loss > 6 %
Fundamentals
Quality Level
Optimal
0.5 level
depreciation
1 level
depreciation
2 level
depreciation
3 level
depreciation
4 level
depreciation
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