There are two methods to achieve this.
- Type the following: avconv -i my-video.ogv -c:v libx264 -preset veryslow -qp 0 -vf scale="1280:trunc(ow/a/2)*2" -c:a libmp3lame -qscale:a 3 -ac 2 my-video.mp4
- Use vlc media player:
- go to "Media" -> "Convert/Save" -> "File" and then add your file
- Press "Convert/Save" and choose "Video H.264 + mp3 (mp4)"
Cheers !!!