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Re: kAudioDevicePropertyStreamFormatMatch rate is zero in Panther
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Re: kAudioDevicePropertyStreamFormatMatch rate is zero in Panther

Hello Bill,

Basically the problem is that some folks are reporting that some PortAudio
apps that worked under Jaguar now fail under Panther. They seem to be apps
that try to lower the sample rate to 8000.0 Hz and are using USB audio
devices.

PortAudio uses kAudioDevicePropertyStreamFormatMatch to find the nearest
match to their desired rate, which made me think it may be associated with
the report from here:


http://lists.apple.com/archives/coreaudio-api/2003/Jul/18/halpatherformatmatchingb.001.txt

We have found that if we hack PortAudio to not change the sample rate, and
just use an AudioConverter to change the rate in software, then the apps
will work.

I do not have Panther so I am waiting for some more reports from users who
are running tests.

I am thinking that it may be preferable to never change the HW sample rate
anyway and just use SW rate conversion. Given that changing the HW sample
rate affects other apps, it seems a bit rude. Maybe we should only change
the rate if someone requests a rate higher than the current rate, like 96
KHz.

But at this point I am more worried by the apparent change in behavior
between Jaguar and Panther. Are we seeing a bug that was fixed, or
introduced, or a new feature?

By the way, the latest PortAudio code is available here:

http://www.portaudio.com/

If someone wants to experiment with this they could try changing the sample
rate in patest_record.c to 8000 Hz and try it with a USB serial device, like
an iMic. I'm not certain that it will reproduce the effect but it is likely
to.

Thanks,
Phil Burk

> >> phil: later that day, Jeff Moore mentioned on-list that it was a bug
> >> and had been fixed. the particular defect i reported
> >> (kAudioDevicePropertyStreamFormatMatch changing a non-zero sample rate
> >> to zero) appears to, in fact, be fixed on my panther system (10.3.1).
> >
> > Great. I will tell my folks to update to Panther 10.3.1.
>
> Unless this is a problem somewhere else, this hasn't been "fixed" by
> core audio - we're not in 10.3.1 - are you sure there's any difference
> here between 10.3 and 10.3.1?
>
> Bill
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References: 
 >Looking for PlayEffect example code (From: Robert Grant <email@hidden>)
 >kAudioDevicePropertyStreamFormatMatch rate is zero in Panther (From: "Phil Burk" <email@hidden>)
 >Re: kAudioDevicePropertyStreamFormatMatch rate is zero in Panther (From: Michael Thornburgh <email@hidden>)
 >Re: kAudioDevicePropertyStreamFormatMatch rate is zero in Panther (From: "Phil Burk" <email@hidden>)
 >Re: kAudioDevicePropertyStreamFormatMatch rate is zero in Panther (From: William Stewart <email@hidden>)



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