RE: [linux-audio-dev] Reference amplitudes and LADSPA (again)

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Subject: RE: [linux-audio-dev] Reference amplitudes and LADSPA (again)
From: Richard W.E. Furse (richard_AT_muse.demon.co.uk)
Date: Sat Feb 02 2002 - 13:57:05 EET


Perhaps we should include a flag on LADSPA plugins indicating that the
plugin is non-linear and therefore cares about input level, plus a
recommendation that such plugins expect peak amplitude around 1. This gives
the host the option to renormalise its signal to 1 on input and output from
whatever representation it uses and a way to know when this should be done.
I'm inclined to modify applyplugin with this in mind. Folk who've written
linear plugins will not notice the difference, folk who've written nonlinear
ones may be in a bit of trouble. Also, has anyone written plugins that map
the floats directly to shorts before processing? Is there much out there
that couldn't be changed easily?

I don't think this should be much more than a recommendation - some plugins
inevitably mess around with peak levels and forcing plugins to keep to these
levels (a) breaks relative scaling when processing two channels of stereo in
parallel and (b) is very artificial and (c) inefficient - a chain of linear
plugins may mess around with signal amplitude quite badly and it'll be much
more efficient to renormalise at one point in the chain rather than on each
plugin.

--Richard


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