Subject: RE: [linux-audio-dev] misc ladspa questions
From: Richard W.E. Furse (richard_AT_muse.demon.co.uk)
Date: Mon Mar 20 2000 - 14:49:41 EET
1. Those plugins themselves are indifferent to their input/output ranges -
they will work in either scheme. It is the host that uses 16bit implicitly
as it only reads and writes 16bit to file.
Personally I don't see a point to the [-1,1] restriction - most plugins
don't care what input range they get for audio but may need some complex
logic (e.g. compression) to guarantee [-1,1] on audio output. This is
likely to result in odd artefacts at points in the signal chain that could
be hard to find. It also makes conceptualising what's going on really
difficult. For instance, consider performing a fast but subtle FM vibrato
by feeding 440+osc(amp=20, freq=880) as the (audio rate) frequency input to
another oscillator. What's the [-1,1] analogue to that?
If plugins do have a preference on their input range (e.g. wave shapers,
noise gates) this can be done through the suggested range parameter
(nasty), or through an input gain control (nice).
2. I think hosts should be free to use their own plugin-location
approaches, but a standard location for shared plugins would be rather nice
- really good idea. I'm no expert on standard UNIX file paths, but one day
Linux may ship with a bunch of plugins - so perhaps a non /local/ directory
would be appropriate? Should we be using environment variables to determine
path? Perhaps there should also be a non-root user convention? (e.g.
~/.ladspa_plugins)
-- Richard
-----Original Message-----
From: Kai Vehmanen [SMTP:k_AT_eca.cx]
Sent: Monday, March 20, 2000 6:51 AM
To: linux-audio-dev_AT_ginette.musique.umontreal.ca
Subject: [linux-audio-dev] misc ladspa questions
Ecasound now has initial LADSPA support. Richard's example plugins work
fine, although I still have to resolve a few issues (the end-user
interface, etc). Anyway, here's some questions:
1. Value range for audio data. I remember someone mentioning [-1,1], but
Richard seems to use the 16bit-range [-32768,32767]. Which one shall
we use?
2. A standard location for the plugins. Any suggestions?
/usr/local/share/ladspa-plugins?
-- Kai Vehmanen <kaiv_AT_wakkanet.fi> -------- CS, University of Turku, Finland . http://www.wakkanet.fi/ecasound/ - linux multitrack audio processing . http://www.wakkanet.fi/sculpscape/ - ambient-idm-rock-... mp3/ra/wav
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