[Jack-Devel] jack vs. motu (usb)

Fons Adriaensen fons at linuxaudio.org
Tue Oct 25 22:28:40 CEST 2016

On Tue, Oct 25, 2016 at 12:49:44PM -0700, Fernando Lopez-Lezcano wrote:

> When using aplay to help debug this it turns out that aplay does not
> complain, and it happily plays the soundfile, but nothing comes out
> of the speakers for the first few seconds - I presume until the card
> switches sampling rate.

Is that sampling rate actually set by aplay, or before by using HW
controls ?
> Once the sampling rate has been defined at least _once_ then Jack
> has no problem to start (over and over again) and aplay plays files
> with sound from the beginning.
> If you access the status and configuration web server in the Motu
> you can switch the sampling rate and you see the clock lock icon
> turn blinking red and then solid white once the change is done.
> Also, alsamixer and amixer show a single read only "control" that is
> actually the lock status indicator (the lsusb descriptors also show
> another r/w control that can be used to _set_ the frequency but that
> is somehow not reflected in the alsamixer/amixer interface).

A few lines of python could probably set the sample rate using the
web interface, wait until the card is ready, then start Jack.
Or find out what's required on the usb endpoint that sets the
sample rate.



A world of exhaustive, reliable metadata would be an utopia.
It's also a pipe-dream, founded on self-delusion, nerd hubris
and hysterically inflated market opportunities. (Cory Doctorow)

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