std.AssumeFPS(clip clip[, clip src, int fpsnum, int fpsden=1])

Returns a clip with the framerate changed. This does not in any way modify the frames, only their metadata.

The framerate to assign can either be read from another clip, src, or given as a rational number with fpsnum and fpsden.

It is an error to specify both src and fpsnum.

AssumeFPS overwrites the frame properties _DurationNum and _DurationDen with the frame duration computed from the new frame rate.