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Q:How do I completely disable thumbnail generation for all video files in Windows XP?

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

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

The above applies to Microsoft's own shell extension. Recent versions of the codec pack come bundled with another shell extension called Media Preview. You can disable that using its own configuration tool.


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:
    (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:
Q:I am not getting thumbnails for AVI files on Windows XP

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

Start -> Run -> regsvr32 shmedia.dll

Q:I am not getting thumbnails for .mkv and .flv files on Windows 7

Recent versions of the codec pack contain the Media Preview and Icaros thumbnail plugins. Those 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 Media Preview or 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.

Q:Why are some of the generated thumbnails completely black?

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 Media Preview and Icaros thumbnail plugins as an alternative for Microsoft's shell extension. These shell extensions will extract a frame from a configurable position in the video (by default at 25% of total video duration) and will give proper thumbnails. So if you are using an older version of the pack, you should consider upgrading.

Q:Why are the thumbnail options not shown in the K-Lite Codec Pack installer or in the Codec Tweak Tool?

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.

Q:Thumbnails are shown for new files, but not for old ones

That can usually be soved by clearing the thumbnail cache.

Q:How do I clear the thumbnail cache?

Windows Vista/7/8:

  1. Run the Windows Disk Cleanup tool:
    Start -> All Programs -> Accessories -> System Tools -> Disk Cleanup
    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.

Q:Why do some thumbnails not have a movie reel?

Known causes:

  1. The video has an unusual aspect ratio.
  2. You enabled the option in the codec pack to hide it.
  3. A Registry key is missing that identifies the file extension as a video format. The relevant key is:
    HKEY_CLASSES_ROOT\.extension, value: "PerceivedType" = "video"
  4. Explorer has been configured to hide it. This is the relevant Registry key:
    HKEY_CLASSES_ROOT\SystemFileAssociations\video, value "Treatment"
    0 = disabled, 3 = enabled
Q:Why are some formats unchecked in Media Preview configuration?

Windows has native support for thumbnailing several formats. For example MPEG and WMV. Those formats may therefore be unchecked by default. If you prefer using Media Preview for those formats, then you can safely enable them.

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