AVSynchronizedLayerTest demonstrates one way of displaying subtitles for a video using the AVFoundation framework. The demonstration project is for a Mac (OS X 10.7) project which demonstrates how to use an AVSynchronizedLayer to display the subtitles with a video playing an in AVPlayerLayer.
To run the project you will have to change the path to the video in AppDelegate.h.
The video either needs to be longer than 1minute 20 seconds or you need to edit the subtitles in setupSubtitles in AppDelegate.m
You can access the source code at https://github.com/ottersoftware/AVSynchronizedLayerTest.