I have Avidemux 2.5.6 on Windows 7 (64).
With some .avi film when I use 'copy', the result is a film that shows only a black screen. I then, instead of using 'copy, convert (to MPEG 4) and the picture is there. It is not a big problem, just an irritation.
From the information Avidemux gives, DIVX, XVID work OK, AVC! does not work and H264 both works with some films and does not with others.
Is there a simple solution?