Re: Capturing currently played audio using CoreAudio on Mac
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 16:41:15 +0100
> I trust that you filed
bug reports at jackaudio.org ....
> We can't fix problems that people
don't tell us about. In addition,
> JACK's operation is very dependent on
the behaviour of the underlying
> CoreAudio driver. Until relatively
recent versions, if you were using
> digidesign h/w, their drivers are so
broken as to make JACK less
> reliable. There have also been CoreAudio
issues with the aggregate
> device that is required if you want to use the
builtin audio chipset
> on an intel mac (the first macs in history not to
have
> playback/capture-capable drivers, for reasons that only Apple
know).
> These have also been resolved in recent versions of JACK for OS
X, and
> its no longer necessary to even create the agg device
first.
Erm, no, sorry, but it's more in the nature of operational
limitations than bugs. I was using JACK to test my app as it can emulate
multi-channel hardware that I don't possess. I just repeated a few of
these tests to refresh my memory and some of the problems have gone away, I
think because I no longer ask for a samplerate that the device (i.e. Jack
Router) does not explicitly tell me it supports.
So the limitations
are:
- both input and output device must be the same
- only one samplerate supported at any one time; to change samplerate the JACK
server must be restarted
- my app hangs if the JACK server is
stopped while it is sending audio output through it (yes, I ignored the warning
message)
A couple of things I noticed along the way:
- just
now I was getting !dat back from AudioStreamSetProperty
kAudioStreamPropertyPhysicalFormat; changing the JACK preferences from 4 virtual
channels to 2 and then back again and restarting my app (which was a necessary
step) made this go away. Now I can't reproduce it. In general, I
observe that JACK configuration changes are not always reported to the app until
the app is restarted, even though I have restarted the JACK server. Maybe
this is by design.
- FYI, there is no way to dismiss the About
box!
Suggest also a 'Preferences' button in the Jack Pilot main
window.
I experienced no problems with any of the CoreAudio devices I
asked JACK to interface with, although these have not been particularly exotic,
and I didn't need to aggregate any devices. I am using JACKdmp 1.9.5, JACK
router 0.9.2, JACK Pilot 1.6.8.
I don't mean to give JACK a bad
press. Far from it, it is an impressive piece of software. I just
find the simplicity and bullet-proof nature of SoundFlower very
appealing.
Paul Sanders.
|
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