[gmpi] Re: 3.9 Time wrap up Try #1
- From: "Martijn Sipkema" <m.j.w.sipkema@xxxxxxxxxxxxxxxxxx>
- To: <gmpi@xxxxxxxxxxxxx>
- Date: Wed, 10 Mar 2004 00:11:56 +0100
> I'm still think there are some problems. Take, for instance, resampled
> playback. In Premiere, we have a shuttle control, which lets the user
> move, more or less continuously, from -4x playback to +4x playback. The
> audio is always rendered at the primary sample rate, but is then
> resampled for output to the audio card. The audio renderer knows nothing
> (and currently cares nothing) about the final output rate. Plus it may
> change between the time that it is rendered and the time that it is
output.
That is basically offline rendering then, i.e. the plugin does not care
about
the actual playback time. It may be possible to support UST/MSC sync
in this case though. Accuracy would depend on whether the playback
rate is contant or not.
> And what about reverse playback in general? Wouldn't we have to tell
> the plugin that the current buffer is actually going to be played
backwards?
UST/MSC sync is more appropriate for sync at the audio hardware
level, i.e. no software varispeed/resampling or reverse playback. Software
varispeed can be made to work I think, but reverse playback really falls
under offline rendering. In fact I think reverse playback might not just
cause problems with UST sync.
> And what about plugin delay compensation. What if you have some plugins
> in the graph which add a group delay to the whole graph, so that it has
> to be rendered early. This can cause, in some cases, plugins to be
> rendered seconds in advance. Is the plugin that is using UST to
> syncronize with some other process going to be able to use the UST here?
Yes, if the MSC is adjusted to compensate for the latency.
> So I guess I can see how you could use UST in a plugin if the stars
> aligned properly. But at least in Premiere it would break down so often
> as to be not worth implementing, in my opinion. So it would have to be
> optional in the GMPI spec, in my view.
I think it probably wouldn't be a bad idea to make UST sync optional.
> So my question is still: If it is an optional host capability, is it
> worth having? If the answer is yes, then I have no objections to having
> it in there.
If UST is not available then the plugin can just fallback to less accurate
sync.
--ms
----------------------------------------------------------------------
Generalized Music Plugin Interface (GMPI) public discussion list
Participation in this list is contingent upon your abiding by the
following rules: Please stay on topic. You are responsible for your own
words. Please respect your fellow subscribers. Please do not
redistribute anyone else's words without their permission.
Archive: //www.freelists.org/archives/gmpi
Email gmpi-request@xxxxxxxxxxxxx w/ subject "unsubscribe" to unsubscribe
Other related posts:
