so I'm combining movie from several clips using AVMutableComposition (which is subclass of AVAsset) and play the preview instantly with GPUImage.
What I want to do now, is crop the video. I've found lots of sample codes how to do that when using AVAssetExportSession, but I can't figure out if it's possible to crop the video 'on the fly', without exporting it first.
So, is it possible to crop AVMutableComposition without exporting the video?