How to add real time audio data to an AVAsset?
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I'd like to add audio data which is generated in real-time (during playback) to an AVAsset/AVAssetTrack. Let's suppose I have a synth generating PCM audio data and I want to play it while showing a video.

I already searched for this in the AV Foundation documentation but I'm overwhelmed by the number of classes and confused by their names. Can anyone give me a pointer to the classes I have to involve?