http://h34nug3iwqjf2376fmmzdhgqivckzemcujmarlptfqeqtq7vya47yyad.onion/2007/05/13/mpgtx-lossless-editing-of-mpeg-video/index.html
It allows you to slice and splice videos without re-compressing them . The video quality and bit-rate (ratio of file size to the length of the movie) stay the same while you chop off the last thirty seconds of your home video or you stick two videos back to back.