Subject: Re: [linux-audio-dev] extending LADSPA, it's not that easy ......
From: Tom Pincince (stillone_AT_snowcrest.net)
Date: Fri Oct 27 2000 - 05:59:41 EEST
>take a gain plugin that is driven by a MIDI CC (with its limited
128step
>resolution).
>Without interpolation you can easily experience zipper noise.
>Add interpolation to the gain plug and the output will be smooth, since
>the plug happily interpolates between consecutive volume parameter
values.
I woke up this morning thinking the same thing. This 128 step
resolution reveals itself sonically in many places. The solution that I
imagined was also for linear interpolation within each block. Thinking
as generically as possible I imagined two entry fields for each plugin
control parameter, one for the beginning of a block and one for the
end. If only one field was used there would be no interpolation. If
interpolation did not apply to a particular parameter then the second
entry field would be ignored.
I also remembered one particular situation that requires a different
method for fades, and that is the short fade-ins and fade-outs that
occur at splice points when assembling composite tracks. It is odd that
I would forget this since there were projects with marginal talent that
required me to do 50 or more of these microscopic fades per day. In
these situations the end points of the fade regions need to be defined
with single sample accuracy. Working with blocks of even 32 samples is
much to crude for this. The program I use allows me to create fade
envelopes for gain automation and has a special fade feature that allows
me to select the fade region with single sample resolution then offers a
choice of 51 fade curves. The fade is computed one sample at a time and
the results are written to a separate fade file that is then connected
to the original audio edl style. I think that the efforts to create edl
standards include fade files of this type.
Prior to following lad my mental image of digital audio was entirely
based on single sample frames, not blocks. Now that I am thinking in
blocks it is challenging to create a mental image that allows single
sample accuracy for anything, even though I use Digidesign software
every day that does so.
Tom
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