QTCH (.qtch) is a filetype used by QuickTime to store audio or video files streamed from a server on the client's computer hard drive. File Format Description The first 16 bytes are: Hex ; ASCII 00 00 00 50 71 74 63 68 00 00 00 02 00 00 00 02 ; ...Pqtch........ This file type seems to have been introduced with QuickTime Player 7.x. The file is normally stored in any sub-directories of the following location: %USERPROFILE%\Local Settings\Application Data\Apple Computer\QuickTime\downloads For example, C:\Documents and Settings\Administrator\Local Settings\Application Data\Apple Computer\QuickTime\downloads\08\02\82580278-44f0f184-c8c435b8-526b4f79.qtch Comparison with QuickTime Player 6.x Previously, QuickTime Player 6.x would store these audio and video (a/v) streams as files on the hard drive that had auto generated names such as 59B8794Ad01. Unlike .qtch files, these files had the correct a/v magic number and could be played by an appropriate player. For example, the first 16 bytes of an m4v file are: Hex ; ASCII 00 00 00 20 66 74 79 70 4D 34 56 20 00 00 00 ; ... ftypM4V ... Using the Firefox browser the location of these files would be: %USERPROFILE%\Local Settings\Application Data\Mozilla\Firefox\Profiles\<session id>\Cache\ For example, C:\Documents and Settings\Administrator\Local Settings\Application Data\Mozilla\Firefox\Profiles\jb4efpu5.default\Cache\59B8794Ad01 File Format Comparison between QuickTime Player 6.x and QuickTime Player 7.x Although the files have different headers their a/v payload can often be the same (see iTunes exception below). In this example the same a/v file was streamed from a server and stored on the hard drive using QuickTime Player 6.x and QuickTime Player 7.x respectively: The first 16 bytes of the file are totally different: QuickTime Player 6.x 00 00 00 14 66 74 79 70 33 67 70 34 00 00 04 00 ; ....ftyp3gp4.... QuickTime Player 7.x 00 00 00 50 71 74 63 68 00 00 00 02 00 00 00 02 ; ...Pqtch........ However the a/v data starts at: 7D 57 3F 1A 9A D6 CE 94 95 59 D0 CE 02 C1 E2 92 From here both files are identical. To prove that the a/v information is intact within the .qtch file you can replace the .qtch file contents above this start a/v hex value with that from the QuickTime Player 6.x file and it will play normally. Identifying embedded file types within qtch It may be impossible to know the filetype embedded within a .qtch file without having a side-by-side comparison with the same file streamed using QuickTime Player