Sets minimum interval between IDR-frames (default: 25). If
scenecuts appear within this interval, they are still encoded as
I-frames, but do not start a new GOP. In H.264, I-frames do not
necessarily bound a closed GOP because it is allowable for a P-
frame to be predicted from more frames than just the one frame
before it (also see frameref). Therefore, I-frames are not nec-
essarily seekable. IDR-frames restrict subsequent P-frames from
referring to any frame prior to the IDR-frame.
