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If the digital outputs of networked devices should to be phase aligned, is necessary to choose a value
that is a multiple of a sample length (1 second divided by sampling rate). For example, given a
requirement of 1ms latency with a sampling rate of 44100 Hz: calculate the number of samples for the
given latency (in this example, 44.1 samples), and then multiply the rounded value (44) with the sample
length (1s/44100). Rounded to the next 100ns, the result is 997700ns.
Table 1. Recommended presentation time offsets < 2ms, in nanoseconds
Rate
2ms
44100
1995500
48000
2000000
88200
1995500
96000
2000000
176400
2001100
192000
2000000
The RME Digiface AVB shows the remaining offset ("input delay") for the first incoming
stream, which is useful to verify that a shorter setting for the existing network can be used
without risking dropouts.
The AVB Tool offers a freely adjustable presentation time offset for each output stream.
In AVB networks, the latency is always specified by the talker and guaranteed by the
listener. This behavior is plug and play and does not require any user interaction or
monitoring.
5.4.1. Adjusting the Network Latency
The default presentation time offset of 2 ms for outgoing streams can be changed when lower latencies
are required.
This setting can only be accessed on the web remote (see Finding the Device on a Network]), where it
can be found in the outgoing stream settings.
Changing the presentation time offset briefly interrupts all incoming and outgoing AVB
streams.
RME AVB Tool User's Guide
1ms
997700
1000000
997700
1000000
997700
1000000
0.6ms
0.3ms
634900
317500
625000
312500
623600
317500
625000
312500
623600
311800
625000
312500
5.4. AVB Network Latency | 24
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