Subject: Re: [linux-audio-dev] gain curves, interpolation, etc.
From: Richard C. Burnett (burnett_AT_tality.com)
Date: Wed Nov 29 2000 - 20:18:13 EET
So if macromedia does it with curves then do it with lines. I would like
to see this patent, I just don't understand how you can patent something
like that. But if you do it line based ( as samplitude does ) and they
don't mention any patents in their literature which they would have to,
then in the actual code you could 'fit a curve/interpolate' between the
points of the line. True its not as good as seeing it as curves, but its
leaving a great function in. I use this all the time. Then at the points
you could pick some sort of dampning factor that determines how the curve
is done, or just have a default.
Also you could do it over the actual wave as samplitude does, or with a
window right below it. Looking at the patent will indicate I hope which
method they use and you can pick the other way.
Just my thoughts :)
Rick
On Wed, 29 Nov 2000, Paul Barton-Davis wrote:
> >This sounds a bit fiddly, and you really don't want to be exposing
> >exponential curves to the user, it wants to look linear, but infact the
> >gain would be exponential. When I'm fading I think of the action I make
> >with a slider, which is more or less linear, but the gain curve is
> >exponential (or something like that).
>
> well, there are two things here: first, most existing DAW's *do*
> expose the user to exponential curves. a typical approach is to offer
> a palette of possible xfade "shapes":
>
> out = linear, in = linear
> out = exponential, in = linear
> out = linear, in = exponential
>
> etc.
>
> second, as far as gain curves in general, keep in mind that as david
> bartold was so kind to point out to me, macromedia owns a patent on
> the use of a visible control curve to manage waveform volume. the
> patent very viable to me. so its unlikely that any open source project
> will work that way. i haven't figured out the generic alternative yet.
>
> however, for edit-point xfades i am thinking more along the lines of
> combining the "palette" approach with the way snd does things with a
> more immediate method of specifying xfade length:
>
> * you get a palette of xfades, which you can add to if you really
> want to
> * the initial width of an xfade is an app-wide default
> * if you click near the xfade (possibly having selected the mouse
> cursor to function in a specific way), the duration of the xfade
> is highlighted, and you can shorten or lengthen it at either
> end, or at both ends simultaneously.
>
> snd has the interesting approach that when you edit an "envelope", it
> is shown with an x-axis from 0 to 1. then, when you apply the envelope
> to a particular region of a waveform, 0 is mapped to the start of the
> region, and 1 to the end. it has some real benefits, and some real
> drawbacks.
>
> >Often you just want a short crossfade. Select a point in two tracks, hit
> >crossfade and it fades around it. If it sounds nasty you make the fade
> >a bit longer. Isn't this the stuff that ProTools makes really easy?
>
> well, i haven't checked protools in a while (BTW - did anybody
> download the free version ? i think the idea of printing out the
> manual is an excellent one, but haven't gotten to it yet). but i have
> never thought of xfades as existing from track-to-track. they exist at
> the points where you insert material from some place into a track.
>
> ardour already does (static, though configurable) xfades for
> punch-in/punch-out, but its the wrong mechanim and its not relevant to
> the editing case (and thus needs to be fixed).
>
> in case its not obvious, despite the fact that i don't plan to add a
> mixer component to ardour-as-DAW any time soon, managing xfades at
> edit points is most sensibly done (i think) by adding complete support
> for gain curves, hence this thread.
>
> --p
>
>
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