[popcornmix]

I have a file which plays normally on Mac OS with codec info reporting a steady 25fps, when I play it on miappa's latest 0413 RPi build it goes crazy constantly switching back and forth between 24Hz and 60Hz about once per second. (Codec info fps also fluctuates between 23 and 25fps)
...
There is a slight pause once per second like a dropped frame so it could well be a 24fps file whose container lies that it is 25fps, but that doesn't explain why it keeps switching to 60 Hz... (my default resolution is 1920x1080 at 50Hz, not 60Hz)

Thanks for sample. The file has timestamps that differ by 40ms (i.e. 25fps), but once a second the difference is 80ms, so there are only actually 24 frames per second.

This seems to be an ugly way of converting 24 fps content to 25 fps. I'm not sure if this was done at source (i.e. on Blu-Ray or by Broadcaster) or in some subsequent conversion.
I can ignore the double length frame differences which stops the unwanted switching.
But you will always have judder on panning shots due to the once a second timestamp jumps.