[ubuntu-studio-users] ubuntu-studio-users Digest, Vol 108, Issue 7

[Pablo Fernández]

El 24/04/16 a las 21:39, Kaj Ailomaa escribió:
> On Sun, Apr 24, 2016, at 08:50 PM, Davide Costella wrote:
>> Hello,
>> tried to follow Kaj's suggestion, but it doesn't work in my case ...
>> I've also tried to "manually" kill jack (using terminal) as Jean
>> suggested;
>> in this case the audio of other app start working again but if open
>> aHydrogen a second time (starting Qjackctl first) hydrogen has no sound
>> even if qjackclt told me server is running.
>> What's wrong?
>> Sorry, I know my questions may sound too noobish for you, but I'm quite
>> new
>> in ubuntu-studio.
>>
>> Thanks again for suggestions (and patience) and further help in advance
>>
>> Regards
>>
>> PS: Maybe the problem is also I've not yet realized how server audio
>> works
>> on linux (I come from windows and this kind of things are a lot simple
>> from
>> a user point of view) is there any sort of step by step guide to better
>> understand this topic, maybe there is no issue in my case and I'm messing
>> around everithing ... :-)
>>
> I'm assuming you are using 16.04?
>
> As background info - both the desktop audio server (pulseaudio) and the
> pro audio server (jack) will use the ALSA backend by default (jack may
> use other backends as well, but the default is ALSA. Firewire devices
> may also use the "firewire", or "ffado" backend.).
> ALSA contains contains among other things the drivers to your audio
> device. Normally, Pulseaudio will have a hold of your audio device
> through ALSA. That is the default, right? But, when starting jack with
> the ALSA drivers, and selecting the same audio device as selected by
> pulseaudio, jack will take over the ALSA backend part from pulseaudio.
> This is why pulseaudio becomes quiet, and you need to make pulseaudio
> connect to jack (which it can, thanks to the package
> pulseaudio-module-jack). So, that is what was discussed before.
>
> In your case, my hypothesis is that the problem may be that you are not
> selecting the correct audio device for jack (happens if you have more
> than one, and it is a common problem). So, after having done a reboot
> (just to make sure), start qjackctl. Choose the device you want to use
> in "Setup" -> "Interface", and start jack using the "Start" button.
> If all went well, jack will have started. So, now start hydrogen. If you
> did not change any settings for Hydrogen, it should automatically
> connect to jack and you should hear sound, and you can double check by
> looking in qjackctl -> "Connect" -> "Audio". If Hydrogen is not visible
> there, most probably you changed Hydrogens settings. In the menu, go
> into "Tools" -> "Preferences" -> "Audio System", and select "auto" in
> the upmost left drop-down menu, then restart Hydrogen, and it should
> work.
>
> If you are having any more problems, let us know at which step, and also
> which Ubuntu Studio release you are on, and we'll try again :).

Also, to kill jack don't use just "killall -9 jackd" but
do a full "killall -9 jackd jackdbus qjackctl".

I have an alias in my .bashrc file that reads
kj=""killall -9 jackd jackdbus qjackctl"
so I just type kj in the terminal when things get a bit weird, jack wise.

This seems to be because, sometimes, having jackd and jackdbus running 
causes
this sort of confusions between jack-aware applications.
  It is not very much of a problem, especially when you get used to 
always start
jack manually via qjackctl, and don't let any jack-aware program to start
jack behind the scenes.

Of course, as Kaj already explained, the most important thing is making sure
jack is started with the right audio interface.

Hope this helps,
Pablo