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Asked: 2026-06-01T19:09:27+00:00

So my question is: what are the valid audio formats to use with ExtAudioFileCreateWithURL?

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So my question is: what are the valid audio formats to use with ExtAudioFileCreateWithURL?

I am recording in a renderCallback from RemoteIO – and have it working using these specs:

AudioStreamBasicDescription :: mFormatID :: kAudioFormatLinearPCM

ExtAudioFileCreateWithURL :: AudioFileTypeID :: kAudioFileWAVEType

But the resulting files are huge, so I want to use a compressed format. I’ve been searching for a few hours and plugging in various format combinations but I get errors:

uncaught exception 'NSInternalInconsistencyException', 
reason: 'Couldn't create file for writing'

I’ve also seen conflicting info about what formats can and cannot be used to record. For a reality check, I tinkered with the SpeakHere example and got it working with kAudioFormatMPEG4AAC – but for the life of me, I can’t those settings to work in my own project.

Any tips on using ExtAudioFileCreateWithURL to record compressed audio?

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1 Answer

  1. Editorial Team

    I finally solved this – recording to AAC directly to ExtAudioFile. Details here: Recording to AAC from RemoteIO: data is getting written but file unplayable

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