Re: Rationale of AudioTimeStamp
Re: Rationale of AudioTimeStamp
- Subject: Re: Rationale of AudioTimeStamp
- From: Jeff Moore <email@hidden>
- Date: Wed, 19 Feb 2003 14:57:31 -0800
The whole notion of being able to move between time bases (particularly
between sample time and host time) easily is key to doing proper
synchronization between multiple audio devices and other parts of the
system like video. Hence, the AudioTimeStamp struct was designed to
hold multiple simultaneous representations of the same point in time.
The more simultaneous representations, the easier to translate to other
time bases.
For instance, the HAL provides both the sample time and the host time
when it calls IOProcs. This reflects the HAL's ability to easily
convert between the two and can be exploited to provide good synch
primitives.
On Wednesday, February 19, 2003, at 01:07 PM, Philippe Wicker wrote:
Hi everybody,
I'm beginning to play with AudioUnit and is for now looking at
parameters passed to to AudioUnitRender method. The AudioTimeStamp
puzzles me. Why is it a struct and not a union? The member mFlags is
basically a 5 bit field, each bit validating one of the members of
AudioTimeStamp. Does that mean that, as an extreme case, we could
receive a parameter with all 5 fields meaningful? What can we expect
in a "normal" use?
Thanks,
Philippe Wicker
email@hidden
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--
Jeff Moore
Core Audio
Apple
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