iOS Capture Video from Camera and Mixing with audio file in real time

Question

I am trying to capture video from iPhone camera and save the movie mixed with an audio file. I can capture the video with the audio (from mic) with no problems. What I want to do is capture the video but instead of mic audio, use a music track (a .caf file). I am capturing the video with AVAssetWriter. I've tried to set up an AVAssetReader to read the audio file, but I couldn't make it work with the AVAssetWriter (maybe because the decoding of audio happens real fast). Also, I don't want to save the movie without audio and mix it afterwards with an AVAssetExportSession. It would be to slow for my purpose. Any Ideas ? Thanks in advance.

Answer 1

Capture the video using AVAssetWriter, Capture audio lets say with AvAudioRecorder , then mix audio and video using AVExportSession , lots of posts on this topic.

Answer 2

If you do it after (with AVAssetExportSession) , you will problem with the sync. and short delay (time...) between the video and the audio...didn't find better solution