Not just QT, also Avi. This is very annoying. I use maya 2017 for the record.
I've also tried putting my settings and timeslider to 48 fps, but every playblast I make ends up at 24fps.
This problem has annoyed animators since the early versions of maya as I see topics complaining about this all over the internet from different points in time. Apparently it's a problem that comes and goes? But I'd have to see it with my own eyes as it's never worked for me before and it would be dumb to believe everything on the internet.
You would think autodesk would be smart enough to simply add a framerate option to the playblast option box when so many people for years on end experience this nervewrecking issue. I'm a student and playblasts are simply the best way to quickly evidence my learning for the teachers to review.
If anyone has an answer please help. I've looked all over the internet, and in none of the topics I've found presenting this issue has it been resolved.