AVPlayer - Benny Hill style speeded up video issue

I'm using AVPlayer to show a live stream. Works fine. Part of my app requires a modal view to appear over the video. Actually, it flips the video view to show the modal view. I want the video's audio to keep playing, which it does fine.

However, the problem is when I return to the video. The video's visuals speed up for a few seconds, Benny Hill style, to compensate for the period they were off the screen. Then the video starts playing norma开发者_开发百科lly. Is there a way to stop this speed up? If not, can I remove the visual element until the speeded up bit stops.