> Date: Thu, 24 Nov 2011 20:45:09 +0000
> From: Fons Adriaensen
> Subject: Re: [LAD] sliders/fans
> To:
linux-audio-dev@lists.linuxaudio.org
> Message-ID: <20111124204509.GA14316@linuxaudio.org>
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>
> On Thu, Nov 24, 2011 at 02:21:25PM -0500, David Robillard wrote:
>
> > Agreed. Everything here is about the *view*. How that maps to
> actual
> > parameter values is an underlying model issue.
>
> Not always. Consider the case of 'VCA' groups for faders. That
> is: you have a slider that controls the gain of a group of
> channels (without those being mixed). The effective channel
> gain (in dB) is the sum of the per channel fader value and
> the one from the group fader. The model sees only this sum.
>
> Now a fader has to go down to zero gain (-inf dB). So you would
> map the lowest possible (finite) value of the widget to something
> that the model (the DSP code) would translate to 'off'.
>
> The question is then: is this exception handled by the widget and
> the DSP code, or by the DSP code only ?
>
> Suppose the minimum value of the widget would correspond to say
> -100 dB if not handled specially. If you just have a single fader
> per channel, you could arrange for the model or the DSP code to
> translate that to 'off'. That is no longer the case if you have
> 'VCA' faders.
>
> There are two thing you'd expect from such a system:
>
> * If either the channel or the group fader is at minimum, then
> the channel must be off (zero gain).
>
> * If the channel fader is at -50 dB, and the group at -60 dB
> you don't want zero gain, but -110 dB. Becaus either fader is
> still in a position where you'd expect that moving it makes a
> difference.
>
> In other words, you'd expect such a system to behave as if you
> had two faders in series.
>
> Now if the DSP code only sees the sum of the two values (as it
> should, having a VCA group is just a user interface issue), then
> that implies that the mapping of the minimum fader position (e.g.
> -100 dB) to something that would be interpreted as 'off' by the
> DSP code (e.g. -9999999 dB) _must be done by each individual
> fader_.
>
>
> Ciao,
>
>
> --
> FA
>
> Vor uns liegt ein weites Tal, die Sonne scheint - ein Glitzerstrahl.
>
>
>