AVB Endpoint application: latency?

[antonioaxel]

Hi everyone,

I've not been able to find any specification regarding the AVB Endpoint kit connection latency.
I understand that it is full duplex, but what is the latency (considering a direct ethernet connection)?

Thank you.

[infiniteimprobability]

What is the latency (considering a direct ethernet connection)?

The XMOS AVB endpoint software supports class A traffic which sets the default media presentation time delay to 2ms (although this is adjustable). This means in a back to back connection, the audio samples (carried over 1722 transport protocol) spend most of their time in the FIFO in the listener, waiting for the presentation time to elapse before being sent to the DAC. Very little time is spent on the wire and in the talker endpoint in comparison.

The general rule of thumb is that 2ms is enough buffering allow up to 7 hops on a 100Mb network. Roughly speaking about half of that delay is the 8KHz Qav shaper and half wire time.

[chmedly]

How low can the media presentation time delay be set? Also, where in the XMOS AVB code is this set? I'm thinking of a daisy-chain scheme where the connection between each hop is a complete talker-listener connection. No AVB streams would be "passing" through the endpoint. Instead the streams would be stripped off and then re-inserted into a new stream on the other side. The potential latency should be much much lower than 2ms for each hop in this situation since several attributes can be statically set. ?