Your second approach is almost exactly what I've done in an iPhone video editing app I've been working on to deal with video previews. Rather than reencode the

Your second approach is almost exactly what I've done in an iPhone video editing app I've been working on to deal with video previews. Rather than reencode the video just to preview it, I can just apply the same transforms (scale, rotation, translation) to the view that's displaying the preview. I then mask that view with another view of the same size so it doesn't go outside the edges. Of course I still need to encode the video with those transforms if I want it to show up in their camera roll later.