Audio jumping between channels on a MOTU 16A

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pemberley
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Joined: Sun Jan 13, 2019 11:33 pm

Audio jumping between channels on a MOTU 16A

Postby pemberley » Sun Jan 13, 2019 11:59 pm

Hi LinuxMusicians,

Hopefully this is the right place to ask this question; feel free to redirect me if not.

I've recently put together a computer partly for the purpose of doing some audio work, hoping that I could use my existing MOTU 16A for conversion. The 16A is class compliant, and I thought that meant it was compatible with any host supporting class compliant USB audio, like my computer running Manjaro.

And it does work! Sort of, and in a very unusable way. If I play a sound on channel 1 and 2, it will generally begin to play on channels 1 and 2 for a few seconds. Then it will begin sounding very bitcrushed and diminish in both quality and level until it's gone. It will then be resurrected on an entirely different channel, fading in in this same crunchy way. Usually it jumps between 1-2, 9-10, and 17-18, if I instruct it to use 1-2. Sometimes it also plays intermittently on all six of these channels.

What's going on? I've tried VLC, aplay, and Reaper, both with JACK and directly on ALSA. I took care to match the sample rates and depths, and tried a few different buffer sizes. Does anybody have experience using such a device on Linux? Could this behavior be a consequence of a bad ALSA configuration? I'm a little stuck. I'm happy to provide any more information that might be useful, and thanks in advance to anyone who responds.

Drumfix
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Joined: Mon Jan 26, 2009 5:15 pm

Re: Audio jumping between channels on a MOTU 16A

Postby Drumfix » Mon Jan 14, 2019 5:31 pm


pemberley
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Posts: 22
Joined: Sun Jan 13, 2019 11:33 pm

Re: Audio jumping between channels on a MOTU 16A

Postby pemberley » Sat Jan 26, 2019 7:33 pm

Drumfix wrote:https://www.linuxmusicians.com/viewtopic.php?f=6&t=18046&start=135


I've successfully patched, recompiled, and installed my kernel! Sorry for the delay, it took some time to figure this out. Thanks for providing this patch; it seems to solve the crunchy audio issue.

However, audio will still jump between channels, seemingly randomly. Any idea what could be causing this? It appears to happen less often with certain buffer settings, but I haven't been able to get audio to reliably play on the channel I select. It's not like the routing is broken in a static way either, since it switches at unexpected times.

Under the least bad buffer settings, audio will sometimes play perfectly well out of the channels I select for ~5 minutes, and then jump off to others without warning.

stanlea
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Joined: Wed Apr 25, 2012 9:49 pm

Re: Audio jumping between channels on a MOTU 16A

Postby stanlea » Sun Jan 27, 2019 8:28 pm

Did you try to settle things in the software interface ? I think that you can plus your 16A as an ethernet device to your router, then find is ip, log in and watch the settings.

pemberley
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Posts: 22
Joined: Sun Jan 13, 2019 11:33 pm

Re: Audio jumping between channels on a MOTU 16A

Postby pemberley » Mon Jan 28, 2019 2:01 pm

Stanlea, I have been using the web interface to do routing, mixing, and configuration, and confirmed that the host and device agree on sample rate, channel count, etc. It's a pretty cool interface!

I've recently gotten the audio to stabilize, albeit on channels other than the specified ones, but it's definitely usable. I had to include the Drumfix patches, and also take care to keep the realtime priority value of the host rather low.

stanlea
Established Member
Posts: 546
Joined: Wed Apr 25, 2012 9:49 pm

Re: Audio jumping between channels on a MOTU 16A

Postby stanlea » Tue Jan 29, 2019 8:08 am

How many channels did you try to record simultaneously ? Did you had any issues with sound (glitches, saturation, numerous xruns,...) ? I am in the process of buying a new card but I really don't know what to think of the MOTUs AVB range. I am considering a 828es.

pemberley
Established Member
Posts: 22
Joined: Sun Jan 13, 2019 11:33 pm

Re: Audio jumping between channels on a MOTU 16A

Postby pemberley » Tue Jan 29, 2019 12:46 pm

Stanlea, I've not done substantial testing yet; I just got it stable yesterday and plan to do more soon, hopefully this evening. I jumpered two outputs to inputs so that I could concurrently test 3 outs and 2 ins with one audio stream, and it worked very well for about an hour, continuously. No interruptions/saturation/channel jumps. ADAT in seems to be working as well.

Oddly, the inputs (including ADAT) seem to be working under the correct channel numbers, but the outputs are not. Channel 1 comes out of 17, 2 is 18, etc. This is a little annoying, but still definitely usable.

I'll keep you posted as I learn more. I've used the 16A with a machine running Windows 7 for awhile, and have been really happy with it. Hopefully I can get my Manjaro box to work with it just as nicely.


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