Thumbnails

Execute the following command to disable the Explorer shell extension that is responsible for thumbnail generation:

Start -> Run -> regsvr32 /u shmedia.dll

How do I disable thumbnail generation for a specific file extension?

You can enable and disable thumbnails very easily with the K-Lite Codec Tweak Tool.

If you want to do it manually, then follow the instructions below.

1. Start the Windows Registry Editor program:
   WinKey+R -> regedit.exe
2. Navigate to the following key:
   HKEY_CLASSES_ROOT\.xyz\ShellEx\{BB2E617C-0920-11d1-9A0B-00C04FC2D6C1}
   (replace .xyz with the desired file extension)
3. Right-click on {BB2E617C-0920-11d1-9A0B-00C04FC2D6C1} and select Delete.
4. Do this same for this key if it exists:
   HKEY_CLASSES_ROOT\.xyz\ShellEx\{e357fccd-a995-4576-b01f-234630154e96}

Execute the following command to enable the Explorer shell extension that is responsible for thumbnail generation:

Start -> Run -> regsvr32 shmedia.dll

Recent versions of the codec pack contain the Icaros thumbnail plugin. That should give proper thumbnails for these file formats. So if you are using an old version of the pack, consider upgrading.

The tips below only apply when using the legacy thumbnail shell extension from Microsoft. It is not relevant when using Icaros.

By default Windows 7 uses its own decoders for video formats such as H.264. The Microsoft decoders do not always work properly when Explorer want to generate a thumbnail. The solution is to change the preferred decoder for H.264 video. You can use the Win7DSFilterTweaker tool (which is included in the codec pack) to change the preferred decoders in Windows 7 (and 8). For thumbnails to work properly you should choose either USE MERIT (recommended), ffdshow, or LAV.

After you have changed the settings, you need to reboot to make the settings take effect in Windows Explorer. You may also need to clear the thumbnail cache.

The black image that you see is the first frame of the video.

The legacy shell extension from Microsoft that is responsible for generating the thumbnails simply works this way for formats that Windows does not support natively. It is unfortunately not possible to change that behavior. The behavior of the Microsoft shell extension is different for file formats that are natively supported by Windows, such as AVI, MPEG, and WMV. With those formats it will try to find the first frame the in the video that is not mostly black and not mostly white.

Recent versions of the codec pack contain the Icaros thumbnail plugin as an alternative for Microsoft's shell extension. Icaros will extract a frame from a configurable position in the video (by default at 25% of total video duration). So if you are using an older version of teh pack, you should consider upgrading. Icaros is available on Windows Vista and newer. It is not available on Windows XP.

If you have a 64-bit version of Windows then the thumbnail options are available in the 64-bit codec pack. That is because Explorer is a 64-bit application. We recommend that you install both the 32-bit and the 64-bit codec pack on 64-bit version of Windows.

On Windows 7, the shell extension that is used for generating thumbnails for non-native formats is part of the Windows Media Player installation. So if you are using a version of Windows 7 that does not include WMP, such as the N or KN version, then the thumbnail options are not available. Same applies if you have removed WMP12. The only way to get the thumbnail options back is to re-install WMP12. In case of the N/KN version of Windows 7, you can do that by installing Media Feature Pack for Windows 7.

Recent versions of the codec pack contains the Icaros thumbnail plugin as an alternative for the Microsoft shell extension mentioned above. Icaros requires that Microsoft .NET Framework 4 Client Profile is installed on your computer.

That can usually be soved by clearing the thumbnail cache.

Windows Vista/7/8:

1. Run the Windows Disk Cleanup tool:
   Start -> All Programs -> Accessories -> System Tools -> Disk Cleanup
   or
   WinKey+R -> cleanmgr.exe
2. Choose C: and press OK.
3. Enable the checkbox for Thumbnails and press OK.

Windows XP:

On Windows XP the thumbnail cache is not stored in a central location, but stored in a hidden file called Thumbs.db in each individual folder that contains videos and images.

1. From Windows Explorer, click the Tools menu, then select Folder Options.
2. Click on the View tab.
3. Make sure Show hidden files and folders is selected.
4. Uncheck Hide protected files and folders.
5. Uncheck Hide protected operating files. Click OK when the warning appears.
6. Click OK to close the Folder Options dialog box.

Now you should be able to see the Thumbs.db file in each folder. Delete it to clear the thumbnail cache for that folder. To quickly delete all such files from your computer, you can use the search function of Windows.