6.x (as above). Tools such as TrID/32 - File Identifier would, when analysing the file in the above example, only give you this information: 75.0% (.QTCH) QuickTime Cached data (9000/1) It would not tell you the embedded file type. Currently the only known way to establish the file type of a .qtch file is to employ a packet sniffer and search for the stream's file type as it is received by the network card. For example, for QuickTime you would search for the leaf atom called ftyp. Even then knowledge would be required to build the correct header to the point of the actual a/v data start. qtch files and iTunes Although iTunes stores .qtch files in the same way as described above the a/v content appears to be scrambled in some fashion so that a side-by-side comparison of the original file with the stored streamed file would find no match in the a/v data. See also List of file formats QuickTime streaming media QuickTime Streaming software QTCH QTCH