Re: clear description of AudioTimeStamp?
Re: clear description of AudioTimeStamp?
- Subject: Re: clear description of AudioTimeStamp?
- From: Kurt Bigler <email@hidden>
- Date: Tue, 22 Apr 2003 11:55:15 -0700
on 4/22/03 11:24 AM, Jeff Moore <email@hidden> wrote:
>
On Monday, April 21, 2003, at 11:30 PM, Kurt Bigler wrote:
>
>
> I am finding that I am getting kAudioDeviceProcessorOverload
>
> nofications
>
> with no gaps in mSampleTime.
>
>
>
> Checking for gaps in mSampleTime seemed like the obvious thing to do,
>
> since
>
> I need to know the number of samples skipped in order to resynchronize
>
> my
>
> buffers.
>
>
>
> However, it appears that mHostTime is showing a gap that is at least
>
> approximately correct. So it looks like I am stuck with scaling
>
> mHostTime
>
> in order to determine the number of scamples skipped, which seems
>
> absurd.
>
>
This sounds like a manifestation of a bug I found the other day that
>
caused the HAL to send too many overload notifications under certain
>
circumstances or an overload notification when what really happened was
>
that the driver returned an error from the kernel trap.
Thanks Jeff. Note that it is behaving _like_ an overload, in the sense that
a callback _was_ skipped. After all, mHostTime had a skip. Would you have
expected mHostTime to skip but mSampleTime not to skip in the scenario you
are thinking of?
So how can I zero in on this? Or do I just have to wait for a future OS
release to find out more about the problem I am seeing?
>
> Is mRateScalar by any chance useful for this? This appears to be
>
> another
>
> field of AudioTimeStamp that is undocumented, except for the phrase
>
> "system
>
> rate scalar".
>
>
The rate scalar field, which only started getting filled out with 10.2,
>
indicates the ratio of the actual sample rate to the nominal sample
>
rate.
Aha, so we really do get some substantial help with on-the-fly sample rate
conversion if we want to do it. That's great. You (I think it was you) had
mentioned this in response to a question several months ago, but you did not
give the details.
Do we really have to log a bug to get these things documented, or are you
also taking notes?
Thanks,
Kurt Bigler
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