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Quick Look doesn't work on mp4 files on Yosemite 10.10.3

Ever since I updated from Mavericks to Yosemite 10.10.3, I've lost the ability to quick look mp4 files. This picture shows what I get when I hit spacebar. What can I do to fix it?

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iMac (27-inch, Late 2013), OS X Yosemite (10.10.3)

Posted on Apr 27, 2015 5:27 PM

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8 replies

Apr 27, 2015 6:57 PM in response to wesjames1986

Ever since I updated from Mavericks to Yosemite 10.10.3, I've lost the ability to quick look mp4 files. This picture shows what I get when I hit spacebar. What can I do to fix it?

Without the stats for the file, more information regarding how the file does or does not play in various media players, or a sample file to examine on my own system, this is all a guessing game. The problem could be anything from a security issue to an atom issue to the use of an unsupported profile like High 4-2-2. As to fixing it, if the file plays in VLC, try reconverting it using HandBrake. All I can say for now is that the issue appears to be associated with the video track which I assume contains H.264 compressed video data and even this has yet to be confirmed.

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Apr 27, 2015 7:40 PM in response to wesjames1986

This is what I get when I do Get Info on any mp4 file on my computer or hard drive

Am looking for something more in the way of a detailed report such as the following:


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The above stats are for another MP4 file that is not QL compatible, does not open in QT X, opens and plays the audio in QT 7 with a "black" display, and plays normally in VLC:


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QT X Player


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Plays like this in QT 7


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Plays like this in VLC


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And plays like this in QT X after reconverting the file using HandBrake. And all of these images refer to just one possible issue—in this case the use of the High 4-2-2 Profile for an H.264 encode.


Have already indicated what you could try to do to fix the issue in terms of a "general" workaround. Did it work? If not, try posting a sample file that can be downloaded and examined by several different people who may approach the problem from different angles.

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Apr 27, 2015 8:08 PM in response to wesjames1986

I don't have MediaInfo on my end but if you are correct, then all my mp4 files may have the High 4-2-2 Profile. Weird thing is my sister's MacBook Air could do Quick Look just fine with these files and she has the same operating system. Did something change with Yosemite and what it will and will not Quick Look?

This is an older, free version of MideaInfo which may still be available for download.


Not trying to imply that your issue is the same—especially since your files appear to open in QT X even if they do not play correctly. Your problem could be something entirely different and may be limited to your computer—e.g., a corrupted file in the QT X player "package." (Yet another reason to have a sample file tested on several systems and in several different players on your system.) I had to reinstall the Yosemite OS last week following the most recent update that apparently corrupted the system and if the files continue to play correctly on your sister's system (and other peoples' systems) under the same configuration as yours—the greater the odds that the problem is in your operating system and not a general playback issue.


Only changes that seem to be stirring up users at this point seems to be the issue of reducing the max QT X playback speed with audio down to 1.9x instead of the old 2x limit. I personally have not noted any changes in QL support following the latest round of Yosemite updates.

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Apr 27, 2015 8:28 PM in response to wesjames1986

I think I may have to do a reinstall of Yosemite. How can I reinstall to make sure things operate correctly? Thanks again for offering tips

You should only have to double-click the Install Yosemite file in your application folder. When I did this, it re-installed Mac OS X v10.10.1 and, after this install was completed, ran the "check for updates" which then installed a "combined" update package that restored my iMac to OS X v10.10.3 but without the problems I was having prior to initiating the re-installation.


In any case, good luck. I'm off to bed.

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Quick Look doesn't work on mp4 files on Yosemite 10.10.3

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