.QTCH File Extension
File TypeQuickTime Cache File
What is a QTCH file?
(Cache|cache file created by QuickTime, a media player for Mac and Windows; saves the cache of an audio or video file downloaded or streamed from the Internet; can be opened in QuickTime Player by changing the file extension to match the original file (e.g., .MP3, .MPEG, .MOV), but only if the file was created by QuickTime 6.5 or earlier.
Beginning with QuickTime 7, the software scrambles the header data of QTCH files so they can't be played by simply changing the file extension.