AVAssetExportSession export fails non-deterministically with error: “Operation Stopped, NSLocalizedFailureReason=The video could not be composed.”

Question

We add subtitles to a video recorded by the user, but the export by our AVAssetExportSession object fails non-deterministically: sometimes it works, and sometimes it doesn\'

Answer 1

I'm guessing that some of your videos' sourceVideoTracks are either:

• tracks that are non contiguous
• tracks with time range shorter than the video's whole time range

The mutable track videoTrack, on the other hand, is guaranteed the correct time range (as instructed by the AVMutableVideoCompositionInstruction) so it always works.