I think I'm mixing up and I need some one to clarify things for me!
What is the differences between GStreamer and FFmpeg. What I need is a command line to convert file(s) from one format to another.
I know I can do that with installing ffmpeg but I read and I saw allot of talk about Gstreamer. Can I use it the same way?
If yes, which one is better?
GStreamer is a multimedia framework used from within applications. It is not generally used directly from the command line.
FFmpeg also has a set of libraries for use within applications but is mainly known for the ffmpeg command. This program can transcode media files and seems more suitable for what you want to do.
To find out how to use ffmpeg, read man ffmpeg.
