Core Audio integer mode
Core Audio integer mode
- Subject: Core Audio integer mode
- From: Hubert Pietrzykowski <email@hidden>
- Date: Wed, 31 May 2017 14:17:34 +0000 (UTC)
Hi,
New to this list, so let me introduce myself. I've done a lot of freelancer DSP algorithm design and programming over the last 15 years (including numerous commercial products). Haven't used CoreAudio too much, one or two simple iOS projects using Remote IO.
Now I face the problem of implementing something more challenging - I need to get the 32-bit integer data from the ADC to the OSX app (CoreAudio-based) without any conversion or any other kind of processing. Seemed easy but I was too optimistic, apparently. No matter how hard I try I cannot make it work. I can successfully enable the hog mode on the device. Once this is done I inspect the input stream format of the device, which is 32-bit floating point. This alone is a little strange, because Audio MIDI Setup says the device input is 32-bit integer (which is exactly what I need). So, the next step I try is setting the stream format (by setting corresponding property). The supported stream formats, obtained from the device by means of kAudioDevicePropertyStreamFormats includes integer streams. To my surprise the stream format does not change when I attempt to set it to the desired spec by calling AudioObjectSetPropertyData with kAudioDevicePropertyStreamFormat selector. The function does not return any error. It's just the stream that remains like it was before. To be more precise - the fields like sample rate do actually change. It's just the flags that always remain 32-bit floating point (value of 9) not matter what I do. Anyone has ideas? Is it possible? I heard the integer mode has been re-enabled in OSX starting from 10.9 if I recollect correctly, so there should be a way. Any help will be greatly appreciated.
Hubert Pietrzykowski
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