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Re: Capturing currently played audio using CoreAudio on Mac
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Re: Capturing currently played audio using CoreAudio on Mac


  • Subject: Re: Capturing currently played audio using CoreAudio on Mac
  • From: "Paul Sanders" <email@hidden>
  • Date: Mon, 19 Apr 2010 17:20:19 +0100

>> - both input and output device must be the same

> JackOSX 1.9.5 should create an agg device if you ask for two different
> devices. If I recall correctly, the issue you think they must be the
> same is primarily a limitation of the JackPilot GUI, rather than JACK
> itself. There are other control front end GUIs for JACK that allow you
> to specify different devices, and you can do so easily from command
> line.
 
OK, thanks, noted.  I'm only smart enough to use the GUI:)

>> - only one samplerate supported at any one time; to change samplerate the
>> JACK server must be restarted

> This is correct. We felt that it imposed too much of a burden on
> client apps to require them to respond to SR changes at any time.
> Apple clearly took a different approach to this with CoreAudio, where
> apps have to deal with SR changes, channel count changes or even
> entire devices vanishing from under their feet ...
 
Yes, living with CoreAudio can be exciting, although devices vanishing is fair enough as they can and do.  What I had in mind, without thinking about it too deeply, was for JACK to offer the samplerates supported by the device it is routing to.  SooundFlower seems always to offer me 44, 48 and 96kHz.  Either it is getting that from the device it is routing to or it is prepared to convert, it's not clear which with the audio hardware I have here.
 
Also, I notice, the JACK server needs to be restarted if another app reconfigures the device it is routing to.  Sorry, I forgot about that one.

>> - my app hangs if the JACK server is stopped while it is sending audio
>> output through it (yes, I ignored the warning message)
 
> JACK will tell every client that it is shutting down. It clients ignore that or don't handle it correctly, there's not much JACK can do :)

OK, I can look into that - I have not investigated in detail.  How do I get told?  I do look out for kAudioDevicePropertyDeviceIsAlive going away, and that code works correctly when, for example, I unplug my Griffin iMic.
 
If I learn something definite from this thread that I think needs attention, I will post a report at jackaudio.org as per your original suggestion.
 
Paul Sanders.
 
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  • Follow-Ups:
    • Re: Capturing currently played audio using CoreAudio on Mac
      • From: Paul Davis <email@hidden>
References: 
 >Capturing currently played audio using CoreAudio on Mac (From: Aron Homberg <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: Paul Davis <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: "Paul Sanders" <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: Paul Davis <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: "Paul Sanders" <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: "Paul Sanders" <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: "Paul Sanders" <email@hidden>)
 >Re: Capturing currently played audio using CoreAudio on Mac (From: Paul Davis <email@hidden>)

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