I have used ffmpeg, but with it you have to first make mpg videos then do cat video1.mpg video2.mpg > joined.mpg and then convert to joined.mpg to joined.mp4 with ffmpeg to be able to upload on youtube. I heard there's mencoder which can join avi files without converting to mpg and using cat command. I'm making videos to upload on youtube so it needs to be avi mp4 or flv format. Which tool is the best to join videos from command line?