[ubuntu-studio-devel] ubuntustudio controls

Len Ovens len at ovenwerks.net
Sat Jun 14 20:43:01 UTC 2014

On Sat, 14 Jun 2014, Ralf Mardorf wrote:

> If you add all users to the audio group, then some users might
> experience issues, when they don't need RT audio, but they e.g. want to
> use transparency windows with FLOSS 3D support, when a full preempted
> (lowlatency) or kernel-rt is installed. Perhaps such a kernel already
> does cause issues, even if the user isn't in the group audio. However,
> my user always join this group and the RT vanilla kernels provide
> doesn't drastically slow down GUI performance when using transparency,
> but preempted and preempted rt kernels can not be used.

As a user of the lowlatency kernel as my default boot (in fact the only 
kernel installed) I don't have any graphics issues from this or being a 
member of the audio group.

> JFTR, keep in mind that for RT nice values are nonsense.

Yup, that is why it is commented out.

> Likely memlock could become an issue too.

I have had no issues... unless memory is too small (< 1G) but then there 
will likely be problems for many graphics creation applications anyway. In 
any case the problems would only show up if there is an application 
running that uses memlock. This would be one of the best arguements 
against running jackd(bus) as session audio backend.

> And please search LAU, LAD, and I guess especially jack-devel threads
> for frantic efforts to provide apps that automatically do set up jackd
> latency settings. IT'S IMPOSSIBLE!

Set up latency? no but we would like to automatically find out latency 
limits. The upper limit doesn't seem to matter too much jackd just 
silently sets the highest it can. For example setting my ICE card for 
-p4096 has the same effect as setting it to -p2048. However, setting jack 
to run at too small a latency setting (for example setting an Intel HDA to 
64/2) will crash jackd. I would like to avoid having a zombie jackd 
running that the user has to kill somehow before they can restart jack.

This is not about the lowest "stable" latency setting for a card. My ICE 
card can be set and start with -p16, but only run at that latency in a 
stable manner with hyperthreading turned off and up to certain CPU use 
levels. The user will have to learn what the lowest latency is that they 
can use for a certain task without xruns. We can't do that. I would like 
to have an "About Latency" button for this reason.

> Don't write an app that fakes to support something, that cannot be
> supported.

No worries.

Len Ovens

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