12 Oct
2003
12 Oct
'03
8:08 p.m.
On Sun, 12 Oct 2003 12:23:41 -0800
"Paul Berry" <pnberry(a)gustavus.ak.us> wrote:
Greetings all:
I am trying to learn about the LADSPA plugins. I have downloaded and
installed the ladspa_sdk, read the ladspa.h header file and read Dave
Phillips article on the O'Reilly network. I've also added the CMT
plugin library.
Okay, so I've got my plugins but I need some helping making them go. I
don't really understand how they work. I am trying to learn about them
in a console environment, that is to say just by themselves (if that
is possible, maybe that is part of the difficulty). I understand the
basics of the C language and the Linux operating system but most of
the information I have found seems to cover developing plugins and
consequently goes right over my head.
The plugins can't be used by themselves - they need a host application,
that provides connections to sound devices, allows you to set control
values etc.
Lets say I wanted to use the sine.so plugin from the
sample library to
play a continuos pitch from my sound card, how would I do that? I'm
confused by the need of an input file for this as I see the sine.so
plugin as the source. Can the output file be a dev file? How about
using the ALSA hw plugin hw:0,0 as the output, how would I do that?
I've read the ALSA library documentation about plugins and LADSPA but
again it goes right over my head.
'applyplugin' which comes with the ladspa_sdk assumes you are processing
.wav files, applying a plugin as an effect. Most LADSPA hosts are GUI
driven, and the only commandline host I have found is ecasound (which
does a whole lot more!) - from the ecasound web page:
http://www.wakkanet.fi/~kaiv/ecasound/welcome.html
example to play a sinewave (under 'effects processing'):
ecasound -i null -o /dev/dsp -el:sine_fcac,440,1
(no input, output to /dev/dsp, use ladspa plugin sine_fcac with
frequency 440, amplitude 1)
Use analyseplugin from the ladspa_sdk to get details of the plugin label
and ports.
Ecasound also comes with a nice interactive cli, which allows you to
build 'chains' of plugins amongst other things. The manpages will tell
you all about it.
-
Myk