Notes about the QTCH file extension:
To open this file type, a required software must be installed. Without it you only see a Windows message "The following file cannot be opened
" (Windows 7) or "How do you want to open this file?
" (Windows 10) if you double-click the file. There click on "More apps"
and choose a suitable software to view such files on your PC or from email attachments.
The QTCH file type is primarily associated with 'Quicktime' by Apple Inc.. This is a cached file but not compressed. If you know the original file format, add the appropriate file extension to the file and it should play in whatever player you use for that format (or in Quicktime). If you don't know the format, see if TrID can identify it for you. iTunes uses this format as well but Apple changed the way these files are handled and they are scrambled in some fashion so you can't just put a new header on the file and get the original media as you could under Quicktime. Also, TrID will not identify the media type; only that this is a Cache file. You could use a packet sniffer to search for the file type of the data stream as it is downloaded but you will still have to manually construct a new header for the file.
Detailed information for file extension QTCH:
Hex: 00 00 00 50 71 74 63 68 00 , ASCII: Pqtch
'Identifying characters' used on FILExt.com are
provided by Marco Pontello from his TrID database
To change file associations press Windows Key
and then Apps and Features
> Default apps
> Choose default apps by file type
Invalid file associations could be the result of underlying issues within your Windows PC.