Subject: Re: [linux-audio-dev] LADSPA/parameter updating?
From: Paul Davis (pbd_AT_Op.Net)
Date: Thu Jul 12 2001 - 16:58:13 EEST
>It looks like LADSPA plug-in's parameters are updated in
>the audio thread. Does LADSPA support the updates in separate
>thread? The problem now is that the updating may break the low
>latency goals.
a LADSPA plugin has control ports. anything that has access to the
port can set the value at any time. whether or not the plugin will
notice is entirely up to the plugin. it can check the port value as
frequently or infrequently as it wishes (it could, in reductio ad
absurdum, ignore it completely).
>In LAAGA the threaded updating is possible but I hope there will
>be a support for it so that I may just provide two plug-ins:
>one for audio thread and one for control thread.
in LAAGA, if you want to control a port, you have to provide your own
(output) port and then connect it to the (input)
port-to-be-controlled. then you modify your own port, and the owner of
the port-to-be-controlled can, as in LADSPA, notice the updated value
as frequently as it wishes.
you may have a thread that receives i/o from some source (X Window,
MIDI, the parallel or serial ports, whatever), and processes the data
it receives to cause control value changes.
however, you can only access port buffers during your client's
process() callback - access at any other time is either "undefined" or
"illegal". so you will need to have the control i/o thread writing new
values to a private location, and then propagate that into the port
buffer during the process callback.
--p ("IMHO")
This archive was generated by hypermail 2b28 : Thu Jul 12 2001 - 16:59:28 EEST