I've spent hours trying in vain to understand the behaviour of an MPEG-4 opened in Firefox. I made it to finish off my reply here:
http://www.magix.info/uk/does-anyone-know-how-to-make-the-end-credits.knowledge.879194.html
It played OK on my PC with VLC (its associated app). I uploaded it to my Dropbox account and posted the link
https://dl.dropbox.com/u/4019461/CreditsPhotos-2a.mp4
But it wouldn't play properly here. FF used Quicktime to open it and it was totally corrupted aftre the firsr couple of seconds. So in FF I went to Tools > Options > Applications and found the entry for MPEG4.
QT wasn't one of the options. And what does 'Always ask' mean? FF never asks me anything.
Anyway, I changed it to 'Use VLC Web Plugin (in Firefox)', and tried the link again. But it didn't work.
So I then changed it to 'Use VLC media player...' and this time closed and restarted FF. The link now plays the video OK.
In summary, there seem to be two issues here:
1. The FF puzzle. Basically I haven't a clue how that facility is supposed to work, or even how those apps were assigned in the first place. In particular, what does 'Always ask' mean? Scores of types have that setting, including ASCII, yet I'm never asked when I click a link to a TXT file - FF just opens it in new tab.
2. Should I expect QT to play my MPEG-4?
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Terry, East Grinstead, UK