Re: AudioGetCurrentHostTime
Re: AudioGetCurrentHostTime
- Subject: Re: AudioGetCurrentHostTime
- From: Jeff Moore <email@hidden>
- Date: Tue, 03 Feb 2009 10:11:46 -0800
On Feb 3, 2009, at 3:58 AM, IainS wrote:
Hello,
(this discussion concerns 10.4.11 [intel and ppc] --- a client
constraint, so "change to 10.5" is not a useful option).
I want to reference timestamped data between a non-audio app and an
audio app.
The AudioGetCurrentHostTime/AudioConvertHostTimeToNanos interface
seems like it should do the trick...
(my simplistic expectation was that *host* time would be independent
of presence/absence of a running audio interface).
However, when I call it from an application with no audio context -
the value returned by AudioGetCurrentHostTime doesn't change.
If I call mach_absolute_time() in the same position - this works fine.
So:
1/ Is this expected behavior (i.e. "Audio" host time doesn't change
unless there's an established audio interface in the app)?
Not at all.
In fact, I just wrote a quick command line tool that spins in a
while(1) loop and prints the return value of
AudioGetCurrentHostTime(). It worked just fine.
2/ Is AudioGetCurrentHostTime == mach_absolute_time() ?
Yup. The API in <CoreAudio/HostTime.h> is actually just a wrapper
around our CAHostTimeBase class from the PublicUtility section of our
SDK (which is a wrapper around mach_absolute_time() and friends).
You can see all the gory details of it's implementation in our SDK.
3/ Is there any reason that I might expect a problem calling these
interfaces on multiple threads?
(I have not seen any difficulty when using these interfaces in audio
contexts).
No. This API is as thread-safe as mach_absolute_time() is.
--
Jeff Moore
Core Audio
Apple
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