iPads are great for recording video but they are pretty terrible at recording audio using just the on-board microphone.
If you want to amplify the audio from an iPad video (or any video format for that matter), you can do so using ffmpeg.
ffmpeg is an open source utility for “trans-coding” – converting from one video format to another. While you’re converting, you can also change things, like the volume.
Here’s my ffmpeg command to increase the volume of a recording
ffmpeg -i “INPUTFILENAME” -vcodec copy -af “volume=25dB” -strict -2 “OUTPUTFILENAME”
You can adjust the 25dB to a higher value if you really want to crack things up. However, this amplifies everything so you are going to get a lot of background pop and hiss but, if you video is useless as it stands, this can be a really useful technique.