Exported .mp4 won't play in Quicktime

I exported a little movie to MP4 and got this error on trying to view it:

QuickTime Player can’t open [name of video]

What am I doing wrong?

I also tried it in VLC and got an error message that says “No suitable decoder module. VLC does not support the video format “undf”. Unfortunately there is no way for you to fix this.”

Which is nice and polite but not a lot of use…!

What version of Quicktime do you have? I don’t have a lot of experience with exporting to mp4, but I just did a little test to see if it works for me, and it opens up in Version 10.4 (855). I hope you find your solution!

Hi John

.MP4 is just the container. In there is the codec you use.
Normally it will be H.264.
“undf” just means “undefined”.
That means, it is just an unknown codec or the file is damaged.

First check to reproduce the film ones more, to make sure, the file is not just damaged … if its not possible try to transform it with a program like: FormatFactory

If you do it again, make sure, you use within MP4 the H.264 codec.


Would you mind sending the video to support@tumult.com? We’ve received one other report of Hype on Sierra producing corrupt videos, so I’d like to see if this could be the same issue.

If you can, please also send a full system profile:

  1. Go to the Apple Menu, choose “About This Mac”
  2. Click the System Report… button and the System Information app will launch
  3. Make sure it is showing the Full information - If the File menu shows “Show More Information” choose that, otherwise you’re good
  4. Choose ‘File > Save’ to save it somewhere (like your desktop), and then attach this file to the email

In the other case, restarting the computer and re-exporting temporarily solved the problem.


I experienced this problem myself today - will submit details to support@tumult.com


Yes, the switch it off/on routine worked (why didn’t I think of that?!). I’ll shortly send you a dropbox link to the animation and the system report.



Thanks, at this point a system profile is the most valuable item I am collecting. Do you happen to have an EyeTV?