Re: [LAU] every first startup of jackd1 with motu ultralite AVB unsuccessful

I do not recall seeing a reply on list regarding this.

On Tue, December 27, 2016 6:07 pm, Peter P. wrote:
> starting jackd1 after connecting a motu ultralite AVB sound
> card throws below error. The second startup attempt works then.
> What could be wrong? How could I debug this further? Thanks! Peter
>
> 12:55:29.917 JACK was started with PID=23950.
> loading driver ..
> apparent rate = 44100
> creating alsa driver ...
> hw:AVB|hw:AVB|64|2|44100|24|24|nomon|swmeter|-|32bit
> configuring for 44100Hz, period = 64 frames (1.5 ms), buffer =
> 2 periods ALSA: final selected sample format for capture: 24bit
> little-endian in 3bytes format
> ALSA: use 2 periods for capture
> ALSA: final selected sample format for playback: 24bit
> little-endian in 3bytes format
> ALSA: use 2 periods for playback
> ALSA: cannot set hardware parameters for playback
> ALSA: cannot configure playback channel
> cannot load driver module alsa

Fernando at CCRMA reported a similar problem on the jackdev list, I think
mentioning a similar problem even when changing sample rates. My guess is
that the device has a PLL with a long time constant for locking the
sampling clock, such that when you send a request for a particular sample
rate the device takes many seconds to report that the requested sample
rate is achieved and the device is ready to use.

The solutions I can think of for a device with such behavior is to make
sure the device is running at the desired sample rate before starting
jackd (e.g. using an ALSA utility to setup the device first, playing
something through alsaplay, etc.), just accept that you have to start
jackd twice, or modify the source for jackd to wait longer or have a retry
loop when a device does not report quick success for setting the ALSA
parameters.

-- 
Chris Caudle
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