OS X Mavericks: Some files may be converted when opened in QuickTime Player

Learn how QuickTime Player in OS X Mavericks converts some media formats when opening them.

When opening media files that use older or third-party codecs, QuickTime Player in Mavericks automatically converts them into a new QuickTime movie. Depending on the length of the original file, there may be a delay before you can play it in QuickTime Player. To minimize the delay, hardware accelerated H.264 encoding may be used during the conversion process on Macs that support it. 

A progress indicator appears whenever media is being converted. If you want to stop the conversion process, click the close button on the window.

QuickTime Player does not modify or replace the original media file. Instead, a new QuickTime movie is created after the conversion is finished.  This new movie can be played, edited, or shared. When you close the window belonging to the new movie, you are prompted to save it for later use. If you don't save the movie, the original media file is converted again the next time you open it with QuickTime Player.


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  •  Files encoded using modern and standards-based codecs such as H.263, H.264,  MPEG-1, MPEG-2, MPEG-4, JPEG, and Apple ProRes open in QuickTime Player without being converted. Several additional professional camera formats play without conversion if Final Cut Pro, Motion, or Compressor are installed on your Mac.
  • Media files that need to be converted when opened in QuickTime Player also appear with a generic QuickTime icon in Finder and Quick Look. Some media file formats, notably .MOV and .AVI, can contain video compressed with a variety of codecs, some of which may need to be converted before playback.
  • QuickTime Player determines which codec to use during the conversion process based on the type of media file being opened. Most older media files, and those that rely on third-party QuickTime codec components, are converted into movies that use H.264. Legacy video workflow formats, such as those encoded with the Animation codec, are converted with Apple ProRes.
  • Optimized encoding settings are used during the conversion process to minimize generation loss. As a result, size of the converted QuickTime movie may be larger than the original media file.
  • iMac, Mac mini, MacBook Air, and MacBook Pro models introduced in 2011 and later can use hardware accelerated H.264 encoding during the conversion process.
  • QuickTime Player 7 plays many older media files without conversion, but it's recommended that you convert important older files to newer formats whenever possible.

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