I'm running OS X Lion. Today I installed Final Cut Pro X and did a couple software updates for that program, and now I find that my Quicktime doesn't play some MP4 files.
A movie that I know for sure played properly before this now has an error box that says "The document "[movie title]" could not be opened. A required codec isn't available."
What is the problem here?
Macbook Pro, Other OS, OS X Lion 10.7
I've noticed the problem with movies that have an empty subtitle track. Try opening the offending movie with Subler. If there is a track checked with the label of Unknown Track, a duration of 0:00:00:00 and a format of mp4s deselect it. Then save the file and try again. If you don't want to do that MPlayerX and iTunes will play the file with no issues.
I don't know what it is about that track that is causing QT to throw the error but it wasn't happening before I installed Lion.
Quicktime X quit playing some MP4 files
