They are not MJPEG, they are AVCHD H.264/MPEG-4 Part 10; 24fps
I have just installed the latest Quicktime and I am still getting this error message
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It appears that QuickTime for Windows is not properly installed.
QuickTime files cannot be read or written without a full installation of the QuickTime
version 7.1.6 or greater components, including the authoring components.
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