Have you restarted your computer?
Yes, sorry I should have mentioned that. I actually installed QT last night, powered the computer off, then tried this morning to see if Photo-jpeg came back.
However, I now recall that when adding QT, I did NOT install the QT viewer (or the updater), only the first item ('QuickTime Essentials') which I assumed (hoped) had all the necessary bits. Could that be the problem?
If this article is accurate:
then whatever my problem is, it isn't due to my not installing the QT viewer. In fact, it states that's exactly what I should have done.
So I'm still at a loss as to how to get Photo-jpeg back, which I absolutely require.
That article (and most of the other ones I've read on the issue) are terribly overblown. For troubleshooting purposes, uninstall QuickTime and reinstall it fully. (Just don't browse the web anywhere super-suspicious and click on a QuickTime component while it's installed.) And try that.
You are doing QuickTime 7, right? Don't do QuickTime X.
THANK YOU, Szalam. I don't know why I was too stupid to think to try that, but I was.
I did as you suggested, and the Photo-jpeg codec appeared (along with many others). I then tried to change QT to remove the browser plug-in and updater, however I got an error message saying QT does not work on Win 10 (or something to that effect).
To shorten the story, it turns out I had installed QT v7.7.8. QT v7.7.9 allowed me to remove everything but the 'QT Essentials' (after installing it with everything), and even after a reboot the Photo-jpeg codec is still in AE's codec list.
So, problem solved. And my new computer did a test render in almost exactly half the time of my old one. So I am thrilled!
Hooray! Glad you got up and running and glad your new machine is so much faster.