Re: Audio delay when using CoreAudio outputs with QuickTime under 10.2
Re: Audio delay when using CoreAudio outputs with QuickTime under 10.2
- Subject: Re: Audio delay when using CoreAudio outputs with QuickTime under 10.2
- From: Dave Addey <email@hidden>
- Date: Wed, 23 Apr 2003 22:45:19 +0100
Hi Jeff,
Yes, this sounds like the problem. Well, guess I need to get my hands dirty
then... unless...
Is there *any* way to point one track of a quicktime movie at two different
output devices (via quicktime, or coreaudio, or anything else)? The only
reason I'm using two tracks (and having this sync problem) is because I
haven't found a way to do this.
I'm not looking for a complete solution: really, just a "yes you can" / "no
you can't". Your help so far has been *much* appreciated in pointing me in
the right direction.
Thanks,
Dave.
On 21/4/03 11:29 pm, "Jeff Moore" <email@hidden> wrote:
>
Your problem is likely due to the fact that the Sound Manager doesn't
>
provide sample accurate synch with compressed audio data. With MP3,
>
each packet of data has 1152 samples. That's the granularity with which
>
you can schedule the data for playback with the Sound Manager since it
>
only can deal with things in terms of whole packets. QT, and all Sound
>
Manager playback clients, inherit this limitation.
>
>
Speaking as a DJ (I spin drum & bass), I can say that 1152 frame
>
granularities for scheduling makes it nigh impossible to actually do
>
beat matching with any degree of confidence. It basically means you can
>
only drop in a new track every 26.1 milliseconds (assuming a 44100
>
sample rate). A typical d&b track spinning at 180 BPM, where each beat
>
spans roughly 333 and a third milliseconds, won't line up on those
>
intervals too often. You're left dropping the track and then nudging
>
the beats into place with pitch bend pretty much every time.
>
>
Your only solution is to take more control over the playback process
>
and decode the data yourself, so that you can schedule everything with
>
sample accurate precision.
>
>
On Monday, April 21, 2003, at 02:57 PM, Dave Addey wrote:
>
------------------------------------
Dave Addey
email@hidden
DJ-1800
Complete MP3 DJ solution for the Mac
http://www.dj1800.com/
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