[linux-audio-dev] XAP: a polemic

David Olofson david at olofson.net
Mon Dec 16 16:57:00 UTC 2002


On Monday 16 December 2002 14.16, Paul Davis wrote:
[...]
> >you can, without loss of information, express both as ticks,
> >and you're back to the uniform timebase.
>
> how so? if ticks are constant-per-beat, i don't see how they can
> express the information without the additional beat-per-second
> value(s). if ticks are constant-per-second, i don't see how they
> can express the information without the additional ticks-per-beat
> value(s). any tempo-synced element to an XAP plugin needs to
> translate a musical time/duration to a tick value (and thence to
> audio frame units). doing this requires two pieces of information,
> one of which is not constant across all musical timelines.

Right. That's why I'd like to think of one timeline as basically the 
full set of information you get in VstTimeInfo, for the full length 
of the timeline. N timelines need N such sets. Audio time is the 
*only* thing they're guaranteed to ever have in comon - and that's 
only for one block at a time. (One can be audio driven, and the other 
sync'ed to a VCR, or whatever.)


> >many uses of tempo-sync only make use of small note lengths
> >(16th, 8th triplet etc) so they do not need this mapping.
>
> i don't think that the note length affects this in any way.

Nor do I. And you should never assum anything like this, either way. 
It's perfectly sensible to have a plugin do some modulation over a 
period of 4 bars, 20 quarter notes, or whatever.


//David Olofson - Programmer, Composer, Open Source Advocate

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