Is it possible to play video from the iPod library in iOS4, or is it still restricted to audio?
I can't find any definite answers, but the SDK doesn't seem to allow video.
No you cannot do that. Check the iPod Library Access Programming Guide, it says:
iPod library access applies only to audio-based media items. You cannot play video podcasts, movies, or television shows from the iPod library.
来源：https://stackoverflow.com/questions/3781620/can-you-play-video-from-the-ipod-library