Quicktime 7.5 for windows won't recognize mp4 format

Not all MPEG-4 files are created equally and some will never play using QuickTime because the codecs are not supported.
Try the free VLC Player to view them.

I am not sure if your problem is the format. It seems there is a change in Quicktime handling mp4 files. Not only does it not recognize them, it hangs quicktime if you try to play them. This change occurred with the iTunes 8/Quicktime update. I have mp4 video files that played fine with previous iTunes, but now hang the system. If I try to play them in Quicktime it hangs. On a Mac you can simply do a Get Info to see if the preview comes up. If it does not, it will probably not import and/or hang iTunes/Quicktime.

Apple is now aware of the problem, I am a Mac consultant and worked with Apple Support to narrow the problem. Just written up today so I am not sure when it will get fixed.

Now, if you want a solution, although it is a work around, it is simple. The same file will import and play fine if you change the extension to .m4v instead of .mp4. .m4v is an Apple extension and may or may not work with other players, but it allows the content to play. For those videos already in iTunes, I believe you will need to move them out of iTunes and then delete the file from iTunes. Then reimport it and everything works.

Try it and see if it makes a difference.

Regarding: 2048-Quicktime cannot play this file because it is not a file Quicktime understands.

FYI -I am using Quicktime PRO

I got this same message over and over when I used my free digital copy of Die Hard 4.

Solution I found: With recent Quicktime update, Quicktime seems to put a CAP on the size of the file it recognize and open.

To get the Digital Copy to work in Quicktime I compressed the File down from 5200 mbs (5.2 gigs) to 1700 mbs (1.7gbs)

Quicktime was then able to play the file and in additional I was able to import this file to itunes.

The unfortunate thing here is that the overall Quality of the file in itunes is now inferior to the quality of the file using Windows Media Player.

What I also found odd was that when I adjusted the file in itunes to play on Apple TV (convert for Apple TV) it increased the file size to 3.2 Gigs and the file plays fine. Althoug once again the quaility isnt as good as in Windows Media Player.

In my opinion this seems to be this is an issue with the Quicktime update. I tried other files out of curiosity and the same thing happened over and over. Quicktime gave me the 2048-Quicktime cannot play this file because it is not a file Quicktime understands: if the file was too large. Compressing the file allowed it to play.

*So My related question is: What is the Maximum File Size that Quicktime will recognize and play?* and *if it its not an error that will be fixed - Why would Apple put a CAP like this in place that directly results in inferior playback quality of a Movie*

Hopefully this will get resolved ...

Message was edited by: simkal