15 Aug
2004
15 Aug
'04
2 a.m.
On Saturday 14 August 2004 08:27 pm, Martijn Sipkema wrote:
From: "Steve Harris"
<S.W.Harris(a)ecs.soton.ac.uk>
A) Forest for the trees
B) Good Enough ® is good enough
On Sat, Aug 14, 2004 at 10:07:06PM +0200, Benno
Senoner wrote:
No, the roundtrip latency is *at least* 100usecs (or whatever), the
hardware will keep re-transmitting until the packets get through.
In pratice people dont really demand hard realtime and it will be OK, but
the maximum time taken to transmit a UDP packet is unbounded, it uses
exponential backoff IIRC.
It is only unbounded if the network can't provide it, and if that is the
case you would lose the ethernet frame, which might be difficult to handle
for something like MIDI. Losing packets is not really hard real time
either...
--ms UDP also
has unbounded transit time. In practice its OK if you dont
want low latencies (just use RTP), but for low latency you really
need one of the non-IP ethernet protocols that can be relaibly used
for audio.
I don't think raw ethernet will buy us anything over using UDP. These
few usecs less simply won't matter.
(but with ethernet you would have the disadvantage that you loose
routability)
On a 100Mbit network the round trip latency between hosts is about
100usecs so the one way latency of MIDI would be
about half of that. and that's form a MIDI point of view instantaneous
because over serial MIDI cable transmitting
a NOTE ON event (3 bytes) takes about 1.1msec which is 20 times slower
than transmitting it over an ethernet cable.