CODEWITHSUNDEEP
iosiphonecore-audionovocaine
Ulrich Vormbrock
Ulrich Vormbrock

Reputation: 379

Frequency analysis - Novocaine and playthrough by mic: how to disable speaker output?

I'm using Novocaine for frequency detection - and it works fine. I highly appreciate the Novocaine framework, as it is performant and easy to use.

Anyhow, there's only one issue: capturing the sound from the iPhone/iPad microphone, I want to disable the speaker output in order to prevent acoustic feedback (noise). How can I do that? Until now, I've tried in vain to change the audio output route. Any ideas are highly appreciated!

Of course, I've found out that independently of the Novocaine framework I can disable the hardware sound - but when I do that, the user gets a kind of tooltip ("sound disabled") which can be annoying to the user. I prefer to disable the sound temporarily as soon as the user hits the "capture sound" button without taking notice of it.

Upvotes: 1

Views: 239

Answers (1)

Ulrich Vormbrock
Ulrich Vormbrock

Reputation: 379

The solution is trivial and I found it out nearly accidentally:

in the output block

[audioManager setOutputBlock:^(float *data, UInt32 numFrames, UInt32 numChannels)
 { ... }

I simply set the output data to zero - after having analyzed (with FFT or convolution or cross correlation or what else) the data:

// silence the sound in order to disable sound feedback
     for(int i=0; i<numFrames; i++) {
         data[i] = 0.0;
     }

That's it!

Upvotes: 1

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