Mpeg To3 GP

Convert Mpeg to 3GP file

Now I expected this to be hard. Or at least take a lot of fiddling to get right. However, it seems to be quite easy. http://www.niemueller.de/wiki/index.php?[[ConvertVideoTo3GP|This]] site has all the goodness. It requires three steps. Now assume we have a file called movie.mpeg and we want to convert it to movie.3GP. The steps required would be

mencoder movie.mpeg -nosound -ovc lavc  -lavcopts vcodec=mpeg4  -vop expand=176:144,scale=176:-2  -o movie.avi -ofps 12

This will extract the video, scale it and reduce the frame rate. Now we need to extract the sound.

mplayer -vo null -ao pcm -af  resample=8000,volume=+4db:sc movie.mpeg

An output file called audiodump.wav will be created that has the audio that we require. Finally we need to combine these two files together.

ffmpeg -i movie.avi -i audiodump.wav  -b 48 -ac 1 -ab 12 -map 0.0 -map 1.0 movie.3GP

And that is that. Next I need to bundle this lot up into a script so I can then forget all about how this works.