30 Nov
2015
30 Nov
'15
3:10 a.m.
Hello Linux Audio Users,
I'm working on a program to drive LED lights based on music playback on a
Linux system. My application creates Jack input ports for frequency
analysis which I'm currently connecting to the Jack monitor ports, this
frequency analysis info is then used for controlling some RGB LED lights.
The application I'm currently using for music playback is Clementine, which
has a Jack sink option.
All this works fine. However, the frequency analysis of the input audio
incurs unwanted latency, so there is a slight delay between changes in the
music and lighting changes. What I want to do is delay the audio playback
to match the full system latency to match the lighting updates as close to
real time as possible.
My current thinking is to route the incoming Jack audio in my application
back to the Jack playback ports, with a fixed delay buffer.
The problem is getting applications, such as Clementine, to connect to my
application's ports instead of the physical output ports. My understanding
of Clementine is that it is using gstreamer, and thus the jackaudiosink
plugin. This plugin appears to have some properties for changing the
default ports it connects to ("connect" and "port-pattern").
Clementine
does not seem to offer a way to specify what ports it connects to though.
What complicates it more is that the ports are disconnected/recreated for
each song.
I suppose I could look into modifying the Clementine code to allow for a
value for the "port-pattern" property to be specified, but I thought
someone on this list might have some better ideas.
Some other thoughts I had:
Is it possible to modify the default system wide Jack playback ports to be
an application? From what I have seen of code that auto connects to the
playback ports, is that it looks for the first input port marked as
Physical.
Is it possible to change the default system wide setting "port-pattern" for
jackaudiosink?
Is it possible to modify jackaudiosink settings on a per application basis
(say with an environment variable or config file) without having to modify
the client program's source.
Thanks in advance for any help on this and cheers!
Element Green
30 Nov
30 Nov
4:55 a.m.
New subject: Changing default Jack output ports to be an application's ports
On Sun, 29 Nov 2015, Element Green wrote:
The problem is getting applications, such as
Clementine, to connect to my
application's ports instead of the physical output ports. My understanding
Personally, I use Pulseaudio with jackbridging and use jack_connect to
tell pulse where to connect it's outputs. PA is always connected
that way no matter what the dumb app does.
Lots of people don't like pulse for historical (Hysterical?) reasons. So
the other thing to do is tell your app not to connect at all and use
jack.plumbing to connect your ports when they appear to the proper places.
Jack.plumbing can be found in the jack.tools package. (jack.plumbing may
be able to disconnect wrongly connected ports as well if the app can't be
told not to connect)
Or, (but wait there's more!) set up an ALSA through port.... what the
people who don't like pulse generally use and what one of them can explain
as I always found it frustrating.... prolly because I was too lazy to
learn
it ;)
Anyway, there is more than one way of doing things. Using jack natively is
probably the best way in the end if you can figure jack.plumbing out.
Note: my wife save hundreds of dollars a month using Skype, so I have
learned to put up with pulse. She uses jack as well because her mic and
guitar use a USB IF while still using the internal outputs :P and it is
easier to do this with jack than pulse alone. Thank you for zita-a2j Fons.
--
Len Ovens
www.ovenwerks.net
6:18 a.m.
Hello Len,
On Sun, Nov 29, 2015 at 8:53 PM, Len Ovens <len(a)ovenwerks.net> wrote:
On Sun, 29 Nov 2015, Element Green wrote:
The problem is getting applications, such as Clementine, to connect to my
I'm certainly not opposed to using Pulseaudio in this case, since the audio
playback does not itself need to be low latency. Though the latency may be
more deterministic in a purely Jack based solution, in order to calculate
the delay to synchronize it with the lighting control.
application's ports instead of the physical
output ports. My
understanding
Personally, I use Pulseaudio with jackbridging and use jack_connect to
tell pulse where to connect it's outputs. PA is always connected that way
no matter what the dumb app does.
Lots of people don't like pulse for historical (Hysterical?) reasons. So the other thing to do is tell your app not to
connect at all and use
jack.plumbing to connect your ports when they appear to the proper places.
Jack.plumbing can be found in the jack.tools package. (jack.plumbing may be
able to disconnect wrongly connected ports as well if the app can't be told
not to connect)
I did not know about jack-plumbing. This looks like the most
straightforward to me and is probably what I'm going to use.
Or, (but wait there's more!) set up an ALSA
through port.... what the
people who don't like pulse generally use and what one of them can explain
as I always found it frustrating.... prolly because I was too lazy to learn
it ;)
Anyway, there is more than one way of doing things. Using jack natively is
probably the best way in the end if you can figure jack.plumbing out.
Note: my wife save hundreds of dollars a month using Skype, so I have
learned to put up with pulse. She uses jack as well because her mic and
guitar use a USB IF while still using the internal outputs :P and it is
easier to do this with jack than pulse alone. Thank you for zita-a2j Fons.
--
Len Ovens
www.ovenwerks.net
Thank you kindly for the great solutions. I was sure there were options,
but its been a while since I messed with this stuff.
Cheers!
Element Green
3314
days inactive
3314
days old
linux-audio-user@lists.linuxaudio.org
2 comments
2 participants
participants (2)
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Element Green -
Len Ovens