From time to time when I need to up the volume of an mp3 I can load the file into CoolEditPro and amplify the file by up to 10db. I am now looking for a way to do this with the audio stream from a video file(.mp4). I know I can rip the audio file from the Video file but its the process of joining both up together again so they are in sync that bothers me. Can someone give me some pointers regarding the software and steps I need to take to achieve this. The reason I want to do this is when I rip a DVD with NeroRecode2 to an mp4 file for the PSP the volume is very low, as it is with most apps that do this job. I would like to be able to amplify the audio stream before I put the file on the PSP.
For mp3 you really ought to check out mp3gain. That way you can increase volume without re-encoding. For mp4, I would suggest that you try aacgain. Same principle basically as mp3gain. Pretty sure that it supports the mp4 container, although you might need to demux to an audio only mp4 first.
mp4s are not muxed like a mpeg1 or mpeg2 file. An mp4 is a container where audio and video tracks are laid out much like Quicktime .mov files. In fact, mp4s were modelled after Quicktime. Having said that, it would be really nice if a developer could take the extra step to modify iVolume or AACgain to work with .mov and .m4v (.mp4) files. It would be as simple as getting the app to ignore the video track(s) in the container, since the data is NOT muxed. There has got to be a growing need for this with the popularity of the iPod video (and iTunes working with videos now). Is someone listening... PLEASE?! I have been waiting for this for 2 years now. I have over 2000 music videos in .mp4 and .mov that need this functionality!
As long as it remuxes the mov to mp4 I guess it would be ok. aacgain is opensource if you want to take a look at it. Hmmm, sf cvs seems to be down, but it should be: http://cvs.sourceforge.net/viewcvs.py/mp3gain/aacgain
