This article does not cite any sources. (December 2009) (Learn how and when to remove this template message)
The topic of this article may not meet Wikipedia's general notability guideline. (March 2019) (Learn how and when to remove this template message)
This article may be too technical for most readers to understand. Please help improve it to make it understandable to non-experts, without removing the technical details. (March 2019) (Learn how and when to remove this template message)
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
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\
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 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[when?] 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
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.