[LAU] Jack & pulse...knickers in a twist.

Len Ovens len at ovenwerks.net
Mon Jun 4 16:54:03 CEST 2018


On Mon, 4 Jun 2018, Mac wrote:

> On Sun, Jun 3, 2018 at 4:22 PM, Len Ovens <len at ovenwerks.net> wrote:
> 
> Yes, I suspect that Qjackctl saved one of the many iterations I attempted and the
> settings were totally bogus.
> 
>  
>       jack_control ds alsa dps capture none dps playback none
>       jack_control dps device hw:0  dps rate 44100 dps period 128 dps
>       nperiods 2 start
> 
> Well that did indeed work.
> 
> I didn't change the hw:0.
> 
>  aplay --list-devices
> **** List of PLAYBACK Hardware Devices ****
> card 0: PCH [HDA Intel PCH], device 0: ALC892 Analog [ALC892 Analog]
> 
> I'm assuming hw:0 somehow used PCH, it being card 0.
> 
> How did you arrive at these values: dps period 128 dps nperiods 2

jackdbus and jackd work differently. Jackd saves the last used commandline 
and if used without any parameters will use that commandline. So using a 
new commandline kills the old one. Jackdbus is different. It stores all of 
the parameters and will reload them at next run. It will only change 
things that the user changes but the old values stay. With your other 
audio device you had set period to 64 in the past and I have found that is 
too small for many internal audio devices (I have one that using 64 
crashes jack) so I went one up. If all you are doing is listening, I would 
suggest that you use 1024 as that would use less resources. In Qjackctl 
terms, period is the same as "Frames/Period" and nperiods is the same as 
"Periods/Buffer". Internal audio devices are designed for A) listening to 
games noise and youtube, B) for using skype. The outputs sound reasonably 
good... the mic inputs, not so much (good enough for skype). The design 
"low latency" for internal devices is 30ms. If they manage at least that 
low they are "good enough" anything lower is accidental.

jackdbus stores device (for a device that is both input and output) as 
well as input device and output device. It seems that if all are set, odd 
things happen. So in any script I use to start jackdbus, I clear the ones 
I am not using. I am not sure what qjackctl does, but I get the idea that 
rather than use device, it gives the same device to both input and output. 
That way the same code can deal with both the same or different values for 
each. In your original output from jack_control I noticed that device as 
well as input and output were set, that is why the line that set them to 
none so that there would be no confusion.

--
Len Ovens
www.ovenwerks.net


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