Re: DefaultOutputDevice timestamps
Re: DefaultOutputDevice timestamps
- Subject: Re: DefaultOutputDevice timestamps
- From: email@hidden
- Date: Tue, 9 Oct 2001 01:02:32 -0500 (CDT)
Hey,
First, I am using 10.1 (I spent a good three or fours of my time to get
it, too) so that shouldn't be cause for anything unless it could be
caused by upgrading to 10.1 rather than doing a full wipe and install. I'm
not used to using flags but I assume that this would be how:
if ((flags & kAudioTimeStampHostTimeValid) ==
kAudioTimeStampHostTimeValid)
{
//do stuff assuming a valid mHostTime
}
Is this correct? If it is, then I'm registering that the
inOutputTime->mHostTime field is supposed to be valid (the mFlags field is
3 so sampleTime and hostTime are marked valid) and yet it still doesn't
update - or at least not when run for only 10 or 15 seconds. So again I'm
lost as to what to do to get a valid host time. I'm trying to think of
ways I could mess this up but since I just take the value given to the
callback function (and log and use it) it seems like this should be idiot
proof. Any ideas on what to do are appreciated as this is pretty important
to my progress.
Thanks much,
Ben
On Mon, 8 Oct 2001, Doug Wyatt wrote:
>
I suspect that you're on 10.0.x and that the flags in the timestamp
>
structure are indicating that the host time is not valid.
>
>
This has been changed for 10.1 - you should see that the valid-hosttime
>
flag is set and you have valid host times.
>
>
See <CoreAudio/HostTime.h> for details about the units, and routines to
>
convert to/from nanoseconds.
>
>
hth,
>
Doug
>
>
>
On Sunday, October 7, 2001, at 03:15 , email@hidden wrote:
>
>
> Hey,
>
>
>
> I'm trying to figure out how to write different signals as output
>
> in a
>
> good synchronized manner but I've hit a snag. For the AudioTimeStamp
>
> inputTime and outputTime I receive as parameters to the IOProc I give
>
> the
>
> default output device, the mHostTime field doesn't seem to really work.
>
> Judging from the NSLogs made while writing to the defaultoutputdevice,
>
> the
>
> mHostTime rarely ever changes. I just ran it where the initial input
>
> sample time was 563.000000 and the input sample time where the mHostTime
>
> (for both input and output) changed was 6605737.000000 - that's 2 and
>
> 1/2
>
> minutes given 44.1Khz sample rate. The mHostTime went from 1224094414600
>
> to 1228389381896 which begs the question (and I know I should know
>
> this) -
>
> what exactly is the unit the mHostTime measured in and what is its
>
> starting reference point (0) based on? In other words, is it based on
>
> the
>
> unix clock (1971) or is it prone to rollover, etc.?
>
> What is it that I'm doing wrong to get mHostTime
>
> to not update? I use the values the default output device gives me in
>
> the
>
> callback method/IOProc that I give it. Since we're supposed to use the
>
> inputTime and the outputTimes as the clock references for our audio I'd
>
> like to figure out how to get it to update properly (and what units it's
>
> in) as I want to try using it for resynchronizing waveform generators
>
> and
>
> wavetable readers.
>
> Thanks,
>
>
>
> Ben
>
>
>
> p.s. Sorry for any poor form but it's 3am.
>
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>
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>
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>
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>
>
>
>
>
--
>
Doug Wyatt
>
work: email@hidden (CoreAudio)
>
personal: email@hidden http://www.sonosphere.com
>
>
"He was the sort of person who stood on mountaintops during
>
thunderstorms in
>
wet copper armour shouting 'All the Gods are bastards.'"
>
-- Terry Pratchett
>
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