AUTimePitch + input notification
AUTimePitch + input notification
- Subject: AUTimePitch + input notification
- From: John Clayton <email@hidden>
- Date: Mon, 15 Dec 2008 08:30:59 +0100
Hi All,
My goal is to sync up the sound being heard to the frames of video
being displayed from a single QT movie. Sound is played via core-
audio and can be pitch/rate shifted via an AUTimePitch - which makes
the real progress through time variable (i do however know exactly
when these rate changes will take place). The core-audio graph looks
a bit like this:
QT Movie -> AUTimePitch -> Dynamics Processor -> Merge -> Output HAL
My thinking so far, is that the best (only?) unit of measurement would
be 'number of frames processed' by the input callback of the
AUTimePitch unit. In that way, I'd know how much data has been
requested from the movie, but its uncertain how much data (and thus
time latency) is introduced by the inner working of the AUTimePitch.
Is there a way to accurately work out the exact frame number of audio
that is presently coming of the speakers assuming the chain above? If
yes, then I can simply use that value + total number of frames in the
movie to work out the right video frame that should be displayed
(taking the graph and video display latency into effect as well at
some point - but lets crawl first, run later).
Thanks
--
John Clayton
Skype: johncclayton
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