starting point of audio output for CoreAudio driver
starting point of audio output for CoreAudio driver
- Subject: starting point of audio output for CoreAudio driver
- From: Tommy Schell <email@hidden>
- Date: Mon, 2 May 2005 15:26:17 -0600
Hi,
I'm trying to sync audio with video from app on output to my CoreAudio
(kernel space) driver.
I'm not clear where I should mark the starting point of audio when
playback begins, to sync with
the 1st video frame.
This is the behavior I observe:
if I do not set setSampleOffset(), then the 1st audio sample written
into the sample buffer via ClipOutputSamples()
is typically around sample 1100.
If I do setSampleOffset to 3200, for example, so that the HAL writes
are pushed forward from my IO head, then the
1st audio sample written is at approximately sample 7500, which happens
to be 3200*2 + 1100, so that it appears
the setSampleOffset value is doubled.
So should I mark the starting point of audio output exactly at the 1st
sample written by ClipOutputSamples(), which would
be approx. sample 1100 (if I didn't set sample offset), and approx.
7500 (for offset = 3200)?
Or should I mark the starting point in the output buffer at sample 0
(for no sample offset), sample 6400 (for offset = 3200)?
Thanks a lot,
Tommy Schell
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