I had an idea yesterday, and I implemented a simple test (see the Movie thread from some minutes):
a. the images are displayed
b. the sound was silent.
So I can watch the movie, but in silence.
This is the default icon (Sequoia):
NB: The QuickTime application behave the same.
Fortunately, I do not decoded the json description file first.
If the QT cannot play it then that tells you right away that the OS does not have the codec.
Mpeg is just capsule, and in that capsule the movies can have various of codes and new codecs come all the time.
Player like VLC is likely to play it. They dont use codecs from the OS but instead their own and they update them all the time.
Xojo obviously can only use codecs from the OS, so if it dont work in QT then it wont work in Xojo.
Exactly my point: useless feature.