@DaveEL: Don't you like my suggestion? 1) It's basically the same, hook vfw in VDubMod in order to write the log with frame sizes. 2) Faster, because you read a txt file. 3) Better, you don't need to write any temp avi file (using /nowrite); and you can do, for debugging pourpose, comptest with 100% of the movie, without taking care if the final size is >4GB. PS: You must discard 2 frames every snip, do you know this? cheers jonny