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Old 10-11-2018, 07:12 PM   #16
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Join Date: Mar 2008
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Originally Posted by JamesPeters View Post
Ok I'll install JACK and do a comparison.

Oops I forgot I'd already installed JACK. Ok comparison done.

Performance with Reaper talking to ALSA directly is approximately the same as using JACK talking to ALSA (when using the same blocksize/numbers/samplerate). The only difference is that the output latency figure is a bit larger when using JACK.

(My test is solely playing audio and using a bunch of ReaPitch instances to max out the CPU. I get it to around 85% and it still works smoothly, and that's when I stop adding plugins.)

You bring up something I hadn't looked at. I get asymmetrical latency numbers with JACK, which is also what I see in Windows using ASIO, but with ALSA I am getting symmetrical values, which are slightly lower on one side. This is what REAPER displays with JACK and with ALSA.

1.4/2.9ms with JACK

1.4/1.4ms with ALSA

I just tried setting ALSA to use three periods, and it now displays 1.4/2.9ms like JACK does with two periods, and after hammering on REAPER while playing back the song it seems as though that might have fixed the frazzing.

I'm also noticing that rather than saying 2/2ch like it does with JACK, it is reading 12/10ch, which makes me wonder if I can now access both cards directly from within REAPER.

Previously the only way I could get both cards to be seen by REAPER was to use Qjackctrl with it's patchbay/router, otherwise the second card would never get any audio into REAPER for times when I'm recording 4 channel acoustic drums.

Will do more testing, but I've now had the song playing in a constant loop the whole time I've been typing this in and it has not gone into frazz mode.

Three MIDI interfaces (two on the two M-Audio cards, and one USB from an Akai pad controller) plus four channel simultaneous audio inputs will be my mission for tomorrow!
Hear My Music - Click Me!!!

Last edited by Glennbo; 10-11-2018 at 07:17 PM.
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