Question

I’m developing an ios audio app on xcode and I’m trying to use 2 audio files I have recorded – which are playing at the same time and export it to one audio file.
All I have managed to do is merge 2 audio files to one, but the 2 audios are playing one after another and not in sync at the same time.
Does anyone have a clue how I can sort it out?
Thanks

Answer 1

You should take a look at this for AAC conversion (http://atastypixel.com/blog/easy-aac-compressed-audio-conversion-on-ios/). It’s super useful.

Another thing you might want to consider… combining two audio signals is as easy as adding the samples together. So what you could do is:

Open both recordings and get an array for each of the recordings that holds the audio samples.

Make a for() loop that adds each sample and puts it in an output array

for(int i = 0; i<numberOfSamples; i++) {
   exportBuffer[i] = firstTrack[i] + secondTrack[i];
}

and then write the exportBuffer to an m4a file.

This code will only work if the two files are the same exact length, so adjust it to your needs. You’ll need to add a conditional that fires if you’ve reached the end of one of the arrays. In that case, just add 0’s.