[LAD] LADSPA extension for periodic control values?

[Stefano D'Angelo]

2009/6/13 Jörn Nettingsmeier <nettings at folkwang-hochschule.de>:
> hi everyone!
>
>
> sorry if this has been discussed before, but i didn't find anything in
> the archives...
> consider the case of periodic control values of LADSPA plugins, for
> instance the azimuth in a horizontal panner or the phase shift in a phaser.
> currently, they are usually marked as BOUNDED_BELOW and BOUNDED_ABOVE,
> but the host has no way of knowing that the upper bound is next to the
> lower bound, so that it can chose the shortest path to the next value
> when interpolating automation control points.
>
> take ardour, for example: if i want to spin a source 360 degrees, i have
> to start at 0, set a control point at 180, set another control point at
> the exact next sample to -180 and then onwards. if there is even a
> single sample between the control points, the interpolation will cause
> the image to jump in weird ways, because it doesn't know that 180 == -180.
>
> does it make sense to add a new hint to LADSPA, something like
> LADSPA_HINT_PERIODIC? it would mandate LADSPA_HINT_BOUNDED_BELOW and
> LADSPA_HINT_BOUNDED_ABOVE as well as the respective port range hints,
> *and* imply that LowerBound is equivalent to UpperBound in the port
> range hint structure.
>
> this would enable hosts to do the Right Thing(tm).

Hi,

I think it makes no sense nowadays to do something like that, for two reasons:

* LADSPA is old, hence old LADSPA hosts will not support that and
new/maintained ones are not likely to support that, since many are
focusing on newer APIs;
* An LV2 extension would allow you to do that quite easily in LV2,
which is probably preferable these days.

That said, I can already hear people who disagree with me shouting and
screaming.

Stefano