I have a number of family movies digitised by a local company, all of which play perfectly on my Linux systems, but none of them play at all on Macs ("The file is not compatible with QuickTime player"). This seems to be a very common problem.

The formats as delivered (or at least the filetypes) are .mpg (for conversion from video tape) and .mp4 (for conversions from cine)

I have been led to believe that AVI, MOV, and MP4 all work on Macs, but my attempts to convert using mencoder all fail with the same error message (above) when I copy the file to a Mac. The command I have ben using is the one quoted on all the web pages I have looked at:

Code:
mencoder -oac lavc -ovc lavc sourcefile.mpg -o targetfile.avi
Incidentally, no matter what output file type I use (.avi, .mov, .mp4), the output file size is identical. This makes me think that it is failing to perform the relevant reencoding because I have omitted some vital piece of information like the output file format — is just the output filetype sufficient or is there something missing. Clearly as it stands it is not doing what the command line implies. I don't care what type of file I have to convert to so long as it plays on an iMac or iPad.