Directshow - Extra frames on video capture to file

[odednaftali]

Hello

I'm writing a video recorder that records input from an external device

I use multipule files capture, and every X minutes i stop the graph, set the output file name to another file and run the graph again.

All in all, seems to be working well, i get multipule video files for my capture.

HOWEVER - for each file, there seem to be extra frames !

Suppose i split the files after 3 minutes, i see that exactly after minutes the first file is done and another one is created, but the first file is 3 minutes and 7 seconds long ! and not 3 minutes and contains 7 seconds of extra frames.
If the split time is longer, there are more extra frames

How is it possible that exactly 3 minutes of capture are written into a 3:07 file ??

I'll be happy for any input

With thanks

Oded