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

  • From: Mike Berry <mberry@xxxxxxxxx>
  • To: gmpi@xxxxxxxxxxxxx
  • Date: Thu, 05 Feb 2004 11:39:22 -0700

Paul Davis wrote:

I am personally OK with not having a GMPI-defined UST. I believe that all of the systems we are talking about running on have some form of independent clock. So if the plugin needs it, it can do it with a system call, or if it is cross platform, it can wrap the system calls per platform. Then it can get the system time at a particular GMPI audio time when it starts, and use that for any comparisons that it needs. While there may be a bit of utility (for plugins) added by having GMPI do the wrapping (i.e., making the host do the wrapping), I think it is more than offset by the complexity of having another time in addition to the 2 that seem to be shaking out of the discussion.

you can't sync with that method. you don't know the relative speed of
the system (UST) clock w.r.t. the sample clock.

for UST to be useful, you have to make pair-wise associations between
it and the other clocks.

UST is not a timebase for use *within* a GMPI graph. its an enabling
feature that allows interaction with things *outside* of GMPI. without
it, that interaction can't be done properly.

Well, if the host is going to provide sync, it is just based on looking at the system time at a particular audio time, or vice versa, and setting a reference point. Why can't the plugin do this itself if necessary? Then the relative speed is just a drift calculation.

Mike Berry
Adobe Systems

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