AVCompositionDebugVieweriOS This sample application has an AVCompositionDebugView which presents a visual description of the underlying AVComposition, AVVideoComposition and AVAudioMix objects which form the composition made using two clips, adding a cross fade transition in between and audio ramps to the two audio tracks. The visualization provided by the sample can be used as a debugging tool to discover issues with an incorrect composition/video composition. For example: a break in video composition would render black frames to screen, which can easily be detected using the visualization in the sample.
2014-04-20 15:16:17.840 owkr_the_movie[45551:60b] *** Terminating app due to uncaught exception 'NSInvalidArgumentException', reason: '*** - [AVPlayerItem setVideoComposition:] AVVideoCompositions using AVVideoCompositionCoreAnimationTool cannot be used with AVPlayerItem. AVVideoCompositionCoreAnimationTool is for ofﬂine rendering only.' AVPlayer Class Referenceに記載