Why some video files can't be played with QuickTime?
The Core of The Problem
That is because QuickTime first check the extension of the file to read the file. If the extension of the file is not one of the formats mentioned in the first part, QuickTime will not recognize it and an error message will pop-out. In such cases, you can just manually change the extension of your file to a QuickTime supported one. Of course, you need to make sure that the codec of your file is supported by QuickTime. This solution is very easy but certain severe problem might occur, for instance, the image of the video might get blurred or twisted. So if you are not very good at codec things, don’t try this one. Is there a better while equally simple solution? Absolutely yes! The third part of this article provides a detailed answer.
Convert Video to QuickTime Format on Mac OS X
Step 1, Download and install QuickTime video converter
You can download it for free here:
To install it, simply mount the .dmg archive by double-clicking it, and copy the application to your applications folder (or wherever you want).
Step 2, Load video filesClick the "Add Files" button to add video files to the program. This QuickTime video converter for Mac supports drag and dropping. It also supports batch conversion, so you can import and convert several multimedia files at a time.

Step 3, Select output format
Use the “format” on the bottom of the window to control the output format. Click on the toggle to the right of the "Format" label to expand the panel. Select "MOV - QuickTime (.mov)" as the output format.

Step 4, Change QuickTime Video and audio Settings

Click on the “Setting” button to expand “Setting” panel.
You can change the Resolution, Encoder, Bit rate and Frame rate of the QuickTime video and Sample Rate, Channels, Encoder and Bit Rate of the QuickTime Audio. The size of the QuickTime file depends a lot on these settings.
Step 5, Select output directory
Expand the "Output" panel. Use the "Browse" button to select an output directory.
Step 6, Click “Convert” to convert Video to QuickTime files on Mac.
