5 Jul
2010
5 Jul
'10
12:28 a.m.
On Sun, 2010-07-04 at 23:05 +0100, Dan Mills wrote:
... IIRC I had around 19 ms for the worst USB MIDI latency. The PCI card
should be tested tomorrow. Even if some had good latencies for USB too,
it seems to be gambling using USB MIDI devices. IIRC all PCI devices had
SUCCESS.
On Sun, 2010-07-04 at 23:35 +0200,
fons(a)kokkinizita.net wrote:
I'll try to use 2 of this Audio/MIDI cards:
http://www.terratec.net/en/driver-and-support/faq_37196.html?selectproduct=…
It would be nice to use both for audio, but the original thought to get
a second card is, to use only one card for audio + MIDI and the other
card for MIDI only, to get two independent MIDI outputs.
If it should be ok to use two cards, a test will show, I assume that
even if audio isn't used, audio for those two cards needs to be synced
at least by S/PDIF?
OT:
Not my machine ...
Well, at least those sound cards that provide
both audio and midi
*could* do this - timestamp incoming midi and provide that info
in some way, and requiring similar time stamps for outgoing midi.
Could do it even with separate midi and audio cards, as long as the midi
RX ISR can somehow grab a timestamp from the audio card driver (in an
interrupt context), and as long as the midi RX ISR is getting serviced
with negligible latency (Otherwise you need to timestamp in hardware).
In reality is is probably only practical in an embedded context where
you have total control over the hardware.
Note that even with this you will have some jitter due to the way a UART
typically over samples to get the centre location of each bit (But at
midi rates this should only be measured in tens of microseconds).
MIDI on general purpose hardware with a general purpose OS is hard to
get really right.
Regards, Dan. ### First the RME results ###
$ alsa-midi-latency-test -i 16:0 -o 16:0 -w 20 -r
SUCCESS
best latency was 0.96 ms
worst latency was 4.04 ms, which is great. ### Next are the midisport results ###
$ alsa-midi-latency-test -i 28:1 -o 28:1 -w 20 -r
FAIL
best latency was 2.95 ms
worst latency was 34.96 ms, which is too much. Please check