Re: [Jack-Devel] speaker management

On Wed, 12 Dec 2012 08:45:00 +1100 (EST) "Patrick Shirkey"
<[hidden]> wrote:
> On Wed, December 12, 2012 7:26 am, Arnold Krille wrote:
> > On Tue, 11 Dec 2012 08:14:35 -0600 David Nielson
> > <[hidden]> wrote:
> >> On 12/11/2012 03:30 AM, Arnold Krille wrote:
> >> > I did something similar two years back: Recorded the
> >> > impulse-response of my home-office, feed them to drc and then
> >> > used the resulting files with jconvolver to correct four
> >> > channels of speakers. I planned to do more but the amp for
> >> > channels 3-8 is a diy-project and time ran out...
> >>
> >> What were the results? I've thought about doing something similar
> >> and wonder if it's worth my time.
> >
> > The results where very good and very worth the time! I started with
> > good quality speakers and a fine listening experience. Then I
> > introduced drc (and used some x-over with fons ambisonics decoder to
> > feed the bass only to the bigger front speakers) and was blown away
> > by the amazing sound. Of course it took some sinus-sweeps to get the
> > room-response but none of the neighbors complained;-)
> >
> > If I find more time for audio again, I might even incorporate such a
> > thing into my live setup.
> >
> > The only downside: when you start doing something with permanent drc
> > and have to run drc and your regular synth/recording sessions on the
> > same machine, you understand fons fighting for session managers that
> > can be told to get out of your way and ignore certain apps with
> > their settings (while still managing the same apps in different
> > instances).
> This seems like it should be a simple flag in the session API. Can you
> explain this issue a little more?

Lets see if I can manage to explain, maybe fons will chip in:

The average jack session is with several apps all used for one project.
you save the project and want to save the settings for all the apps.
you restore (aka load) a project and want all the apps to come up again
with the correct settings. All current session managers aim to make
this as simple as possible (preferable by even supporting apps that
don't have native session-management support). And thats a fine goal.

But when you do drc and/or ambisonics you end with a setup slightly
more complicated: there are some apps that are independant of the
project and stationary to the machine. Some of these apps might even be
the ones all the other apps should use as "hardware outputs" instead of
the real hardware outputs.
No problem when a) the session manager ignores these apps and b) the
project is not meant to be movable to a different machine.
By making session-management easier for 'most' people, todays session-managers
break a) and forcefully support apps that don't want to be supported.
And as neither jack supports something like static port aliases nor
as session-managers correctly support the notion of distinct apps
as "the global environment", b) breaks. Because nowadays the session
connects to "alsa_pcm:playback_[12]" on one machine and has to connect
to "jconvolver:in_[12]" on another machine.

So while session management nowadays is easy for 'most' people and
use-cases, its actually made impossible for these special cases.
Special cases like: I have this super-cool ardour-project using two
dozen synths and playing out to my native home-cinema surround-set. And
the audio is so cool that I want to play the same project on one of the
bigger ambisonics/wfs setups at the next LAC. Only my project connects
to 'alsa_pcm:playback_[1-6]' and when I do that on the wfs-machine I am
lucky when nothing of the hardware breaks because I sent my bass-beats
to the highest speaker of a four-way...

> If the app doesn't have support for jack session management how can
> the session manager be in the way?

See above, when you write a session-manager for audio and want it to be
used, you support apps that don't support you...


There are probably some easy solutions to these problems outlined
above. But its "special cases" and it seemed to me the last years that
many developers don't want to deal with this and don't want to listen
to the people that have to deal with this.

But I am happy if I am proven wrong: if there is a session-management
for audio-projects that knows which app is part of the project and
which is part of the environment. If there is even a session-management
that knows about something like "the environment" apart from
alsa_pcm.

Have fun,

Arnold

1355269655.25168_0.ltw:2, <20121212004654.7d612d37 at saratoga dot arnoldarts dot de>