Complex sentence: For a long time the specifications of the codec were not public, and the only way to play back Sorenson video was to use Apple's QuickTime, or the MPlayer for Unix/Linux, which in turn piggy-backed Microsoft Windows DLL-files.
Split into simpler sentences: For a long time the specifications of the codec were not public. Previously, the only way to play back Sorenson video was to use Apple's QuickTime, or the MPlayer for Unix/Linux, which in turn piggy-backed Microsoft Windows DLL-files.