Peculiar anomaly when reducing file size.

[Bunyip]

I have an MPEG file of 604MB in size (Video 1). When I reduce the file size by converting it to an AVI file the new file size is 375MB. Everything OK so far.
However, I also have a similar MPEG file of 568MB in size (Video 2). But, when I reduce the file size of this one by converting it to an AVI file, using exactly the same conversion settings as I used for Video 1, the new file size is 489MB.

This doesn't make any sense at all!! Logic dictates that the converted file size of Video 2 should be smaller, NOT larger, than the converted file size of Video 1 because the original file size of Video 2 is smaller than the original file size of Video 1.

Is there a fault with Media Converter, or is there some logical reason for this peculiar anomaly?

[DeskShare_-_Support]

Compression rates vary a great deal depending on the details of a particular movie. The two MPEG files could have been created using very different settings, which would mean that recompressing them to AVI would not necessarily give exactly the same improvement in file size.

Also, even when using the same compression settings, different movies will compress differently because the compression ratio depends on the actual contents of the movie, for instance how many scene changes there are.