Re: [linux-audio-dev] LADSPA unbounded control values

New Message Reply About this list Date view Thread view Subject view Author view Other groups

Subject: Re: [linux-audio-dev] LADSPA unbounded control values
From: Paul Barton-Davis (pbd_AT_Op.Net)
Date: Wed Nov 22 2000 - 16:25:56 EET


>> without an upper bound (mono amplifier). the port is also hinted as
>> being suitable for logarithmic control. i am probably just being
>> dense, but it seems very difficult to pick an arbitrary upper bound
>> *and* use a logarithmic transform and still get meaningful results.
>
>Seems to me that the term "logarithmic" isn't quite right. If one thinks
>in dB as all engineers should, it's immediately obvious that a 0dB
>reference point must be specified. So my take is that its not the lack
>of an upper bound that's the problem, it's the lack of a 0db reference.
>This applies even if the bounds are set - where is 0dB on the scale? My
>best guess is default to 1.0 and hope for the best.

this was my first guess as well. the problem is two-fold.

1) the "amplifier" is useless if the maximum value of the gain
   value if 1.0 (it can never actually amplify)

2) the LOGARITHMIC hint is intended to apply to more than just
   dB-related controls.

my short-term hack has been to use a UI-presented range of lower..4.0
as the upper range, and to set the actual control value to x*x*x,
where x is the value "set" by the user interface. this gives
reasonable results but is clearly utterly wrong.

perhaps the problem is just with this plugin, and it should really
specify an upper bound, which would reflect the maximum gain the
plugin could deliver. there is still the problem of converting the
the control value into an actual gain, since if the specified range is
0.0 to 1.0, what does 0.0 actually mean ? its meant to indicate
"-infinite" gain, presumably. all very confusing.

    


New Message Reply About this list Date view Thread view Subject view Author view Other groups

This archive was generated by hypermail 2b28 : Wed Nov 22 2000 - 17:45:07 EET