问题
Is it possible to process the audio and increase its base volume?
Please do not suggest to increase .volume property. I am looking for way to increase volume of already recorded audio programmatically and save that audio with big volume level.
I am recording from speaker.
回答1:
There are a couple ways of doing this. Normalization and Compression are the two that come to mind. See the links for better explanations.
Audio Normalization - calculate the current loudest sample in the file, and then apply equal gain to every sample such that the loudest sample is now at max volume.
Dynamic-range Compression - reduce the gain of a sample or group of samples when they exceed a threshold, and then apply gain to the whole file to compensate for this reduction.
iOS APIs may have a way of doing these already, though I'm not sure. Hopefully this gives you some rope to grab onto.
来源：https://stackoverflow.com/questions/37822286/ios-increase-volume-of-recorded-audio