[LAD] Audio over net - an observation

Focusrite's RedNet series of interfaces uses Dante as the transport
protocol. Going to the Dante home page I find that an audio driver
(mac/win) is available for $30 or so (there is apparently a linux version
available from another party). Yet Focusrite sells a RedNet PCIe
card for around $800... one hopes it has more on it than an ethernet port
:) That looks like a sound card to the computer. This card does not look
like it has a special plug on it (like the locking ones some of the
snake/mixing boxes have). I am wondering what other processing might be
happening on this card to make it worth Focusrite's effort to produce.
Routing to be sure, but the Interface boxes all have that anyway. DSP?
Effects? maybe, but not useful on a Linux box I am sure.

I realize a big part of the cost is scale (lack of scale in this case),
but can't help but think that the money would be better spent on a better
mother board. For example moving from an i5/7 to a Xeon based board.

Reading more about the RedNet PCIe card. It is 4 lane, but the recomend
installing in an 8 lane slot. They also recomend using a GB switch to
which both the PCIe audio card as well as the MB native Ethernet port is
connected. They are suggesting that all the audio will go through PCIe AI
card and that control will go through the native enet port. This all may
be to do with 128 channels at 192khz at 3ms. The native enet port has the
dante driver on it too.

I am not suggesting that the Linux world embrace Dante as a protocol so
much as learning from its implementation. I am not sure that building for
192k is the way to go though.

Some numbers... if they are talking 192k with a 32sample buffer (like jack
with 16/2?) it would seem there is a lot of extra latency built in as at
48k and 16/2 the raw latency from card to jack is only .6ms and at 192k it
would be less than .2ms... .3ish for return trip. So the network and ADC
together take a lot longer. Considering my USB IF at 48k has an ADC time
of ~.5ms, most of that is network.

I am looking forward to testing Fons' n2jbridge jack backend. I will not
be using 192k however. I generally use 48k, but may try 96k to test
differences in latency. My own low level protocol is way down the road, if
it ever happens.

--
Len Ovens
www.ovenwerks.net
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