Hi Patrick.

I’m trying to write my own hi-res audio player. I’ve already been successful in 
playing a 24/192kHz audio file on both iOS and macOS using code based on what 
is written here: 
https://developer.apple.com/library/content/documentation/MusicAudio/Conceptual/AudioQueueProgrammingGuide/AQPlayback/PlayingAudio.html
 
<https://developer.apple.com/library/content/documentation/MusicAudio/Conceptual/AudioQueueProgrammingGuide/AQPlayback/PlayingAudio.html>

However, the CoreAudio system automatically converts the sample rate internally 
to whatever the output rate is set to (via Audio Midi Setup on Mac, and some 
unknown method on iOS).

On iOS, you can set AVAudioSession.sampleRate, but output still won’t go higher 
than 48kHz.

I’m using an XDuoo XD-05 (http://www.xduoo.com/xduoo/En/ProductView.Asp?ID=17 
<http://www.xduoo.com/xduoo/En/ProductView.Asp?ID=17>) with a display, so it 
tells me what the phone is outputting. I can use Onkyo player to play at 
24/192kHz, but I can’t get my own app to play at any more than 48kHz. Sample 
rate conversion is precisely the thing I am trying to get away from.

Thanks.

-Kenny


> On Apr 18, 2018, at 12:12 PM, Patrick Cusack <[email protected]> wrote:
> 
> Your output device is going to determine your sample rate. Any audio you play 
> is going to be float so 24 bit isn’t a consideration as you will convert the 
> 24bit audio to float. As for your 192kHz audio, you will either need to play 
> it out of 192kHz device or perform sample rate conversion in your audio graph.
> 
> This stack overflow listing discusses handling sample rate conversion:
> 
> https://stackoverflow.com/questions/6610958/os-x-ios-sample-rate-conversion-for-a-buffer-using-audioconverterfillcomplex
> 
> 
> 
> 

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