[LAU] Realtime issues with USB-device [

[David Kastrup]

Michael Jarosch <riotsound at riotmusic.de> writes:

> It's me, again!
>
> Using a realtime kernel, I struggled with xruns on my Focusrite
> Scarlett 2i4 (1st gen) and just wasn't able to work it out. Guess, I
> didn't manage to include the device into rtirq's list of interrupts
> with high priority…
>
> Surprisingly, using a standard debian kernel solved it. Still, I would
> love to understand, how to configure rtirq to make a usb audio
> standard device just work… I ended up setting the interrupt numbers
> [16,23] to RTIRQ_NAME_LIST without any success on the xrun front. But
> maybe I should have done anything else? I configured my system doing
> all the things mentioned in
> https://wiki.linuxaudio.org/wiki/system_configuration AND verified
> this and more with the rtcqs scripts.
>
> The linux-show-player issue is also persistent…

Which sample rate, which period size and count?  Personally I have found
that using a period size of the form 3*2^n rather than 2^n can
surprisingly improve results at 48kHz or 96kHz of sampling frequency,
likely due to the timer interval becoming better expressible in terms of
system ticks and/or milliseconds.

That can lead to a period size of 256 being problematic and a size of 48
samples working fine, depending on the device and drivers in question.

-- 
David Kastrup