WavTap | globally capture whatever your mac

Three things look wrong:

1. You declare that the format ID is kAudioFormatMPEG4AAC, but configure it as LPCM. So try

   monoStreamFormat.mFormatID = kAudioFormatLinearPCM;

   You also call the format "mono" when it's configured as stereo.

2. Why use mach_timebase_info which could leave gaps in your audio presentation timestamps? Use sample count instead:

   CMTime presentationTime = CMTimeMake(numSamplesProcessed, 44100);

3. Your CMSampleTimingInfo looks wrong, and you're not using presentationTime. You set the buffer's duration as 1 sample long when it can be numSamples and its presentation time to zero which can't be right. Something like this would make more sense:

   CMSampleTimingInfo timing = { CMTimeMake(numSamples, 44100), presentationTime, kCMTimeInvalid };

And some questions:

Does your AudioBufferList have the expected 2 AudioBuffers? Do you have a runnable version of this?

p.s. I'm guilty of it myself, but allocating memory on the audio thread is considered harmful in audio dev.