perian installation

As others state - Perian is not supported on OS X anymore. The standard Quicktime in 10.10 will not use any of the codecs Perian installs, only the outdated Quicktime 7 will use them.

To be more specific, the Perian codecs cannot be used by the "AVFoundation" for playback but most Perian codecs are still used by the system "Convert" module allowing the QT X v10.3 and v10.4 Players, as well as, the Mavericks and Yosemite Finder accessed routines to convert codecs. Unfortunately, I believe the Perian DTS codec is still incompatible with the convert module and still creates and "empty" audio track for converted DTS source content.

As others state - Perian is not supported on OS X anymore. The standard Quicktime in 10.10 will not use any of the codecs Perian installs, only the outdated Quicktime 7 will use them.

Try VLC to see if it can play the files, it supported on 10.10 & plays a wide range of codecs…

http://videolan.org/

Apple expect you to convert any old formats to keep using them.

Click here and download it or NicePlayer. Note that on Yosemite, you'll also need to download QuickTime Player 7 to make full usage of it.

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Perian may no longer be compatible with Yosemite. Installing is very simple. Double-click on the icon and Perian is installed as a System Preference.