Today I needed to convert an MP4 video, shot via cellphone to MPEG, so it will be viewable on a all platforms.
ffmpeg, is a tool for playing and converting a movie or audio file from one format to another. The process itself is called transcoding.
ffmpegX includes many video and audio codecs – MPEG, MP4, AAC, Flash (FLV), etc.
Even though it has some UI quirks, ffmpegX is a great tool for converting movies and audio files from one format to another.