Play audio data, but without sound?

Question

Created Apr ’17

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I am working with analog medical (eeg) data. I'm trying to allow for recording and scanning large files ~20-30 minutes in length. Core Audio seems like a great solution for storing and playing these files, however the catch is that I do not want to send any sound to an audio device. Everything is output graphically as waveforms. None of my considered solutions seem satisfactory:

1. AudioComponentDescription.componentSubType = kAudioUnitSubType_GenericOutput for the output node seems similar to what I want, but since it isn't tied to the timing of a hardware output device, it wouldn't let me play files in real-time at the same speed they were recorded.

2. Playing the file with the volume turned down, or with the mixer node disabled is a possibility, but when I tried it I got zeroed out audio playback (logical but unfortunate in my case)

3. Having a NSTimer callback repeatedly call ExtendedAudioFile.ExtAudioFileSeek is another possibility, but seems like it is very much not how ExtAudioFileSeek was intended to be used.

Is there a simpler way to do this?

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Answer 1

NB Systems OP

Apr ’17

Can you say, what you´re goal is ???

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Answer 2

slmille4 OP

Apr ’17

Sure, EEG data is analog data which is typically viewed as a waveform plot and/or spectral frequency display. Playing the recording as audio isn't very helpful, so I only want to display the information visually. I have it working in a UIScrollView by using ExtAudioFileSeek, but I'd like to be able to play the files back in real-time as well.

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