[gmpi] Re: Reqs 3.9. Time - opening arguments.1

  • From: Chris Grigg <gmpi-public@xxxxxxxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Wed, 4 Feb 2004 22:52:17 -0800

>>they *never* agree (more or less). to repeat: UST is there to act as a
3rd party mediator when a plugin needs to sync a time derived from
GMPI's master "sample clock" with another non-GMPI streaming sample
clock (e.g. video vertical retrace clock)

Thanks. Sorry to be dense... can you walk us (maybe just me) through a concrete example of what a plug would actually do with a UST that arrives in an event? Also is this only useful for clock event streams (like the event represents a tach pulse or the leading edge of the hammer in a vertical retrace interval, etc.)? Would I ever use the UST time if the event were a note?

no.


it would be used if you had a plug that was (say) playing video (say,
to some external high-res sooper-dooper moni
tor, or maybe even over a
network or something). the plugin would know the UST associated with a
given retrace start. it could then check the current audio transport
time for the same UST, and know how much to correct video/audio drift
by.

nothing new here - i am sure premiere et al. do this all the time.

you just can't do this correctly without the "neutral 3rd party", and
UST is the best candidate for that anyone has told me about.

--p

ps. and many thanks to martijn sipkema for years of education about
    this :)

Thanks, Paul, that helps a lot.


It's starting to sound like UST event time will only be used by certain kinds of plugs, i.e. ones that care about other/outside sync sources, not by all plugs. An ordinary music synth or an effect processor with no external sync issues wouldn't ever use a UST event time, and could get along with only a sample-based event time. Similarly, musical time is only needed by certain kinds of plugs. Is this right?

If so, then I buy the idea that all events need sample-based time, since that's how most plugs will know where during their process() loop to execute the event -- but I don't get why all events need to also have a UST time. As somebody or other has been claiming.

-- Chris G.

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