How demux H.264 AVC MP4 with AAC audio?

[gopackgo]

I have a video I converted using Videora that outputs H.264 video and AAC audio in a MP4 container. I want to make the audio louder. How do I demux the audio and then remux it back. I am going to use MP3Gain to make it louder. Thanks for the help!!

[allanon019]

you can use Yamb. There's also MP4box, but it's more complicated to use.