[gmpi] Re: Reqs 3.9. Time - opening arguments

  • From: Paul Davis <paul@xxxxxxxxxxxxxxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Sun, 01 Feb 2004 15:39:29 -0500

>       There is simply no way that Premiere (not a simple host) is going to 
>have a GMPI plugin controlling time in our graph. As an audio/video app, 
>it is already a difficult task to negotiate timing. We have video 
>devices, audio devices, display devices, and all of them want to be the 
>master timing controller. If we have to allow some (audio) plugin(s) to 
>also jump into the mix, that is too much. If phrased as a must, that 
>would be a show-stopper for us.

Mike, I can only guess at how Premiere's architecture is organized
with respect to time, but I would make this observation based on
Ardour's own video/audio connectivity (the video in this being
animatics rather than pure video, but the principle is the same):
having a plugin control the *musical* timeline (bars|beats|ticks)
doesn't inherently have to have anything to do with inter-media sync. 

when a plugin changes the position of the bar lines/points from a
musical perspective, it doesn't have any impact on the timeline
measured in SMPTE frames, or audio frames, or minutes:seconds.

this is why UST is so important as a "medium of exchange" between
different data streams. if you can always map from a time Tm (specific
to media m) to UST and back again, then you can also always map from
Tm to Tn (where m and n are different) media, as long as you have the
corresponding UST times available. 

given that GMPI is an audio/music plugin API, it would be a mistake to
allow plugins to control any sense of absolute time, partly for the
reasons you describe (i.e. the plugin cannot possibly understand all
the interacting factors). but allowing a plugin to "contribute" its
notion of musical time seems pretty innocuous to me. i may well be
missing something the size of greenland here, however :)


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