On Windows 10/11 you can install some additional Media Foundation codecs for WMP. This will allow you to play some additional video formats, such as HEVC and VP9.
Rename your file from so it has extension .video instead of .mp4/.mkv
This forces WMP to use the DirectShow codecs from K-Lite instead of the Media Foundation codecs from Windows. The codecs from K-Lite work better than the ones from Windows. This solution should allow you to play everything, including subtitles.
Codec Tweak Tool > Media Foundation > disable for .mkv or .mp4
This will also force WMP to use DirectShow codecs. Warning: This tweak will break playback of such files in applications that require Media Foundation. Games and web browsers often need Media Foundation, so we strongly advice against using this solution. Please read the help file in the Codec Tweak Tool.
Use Media Player Classic (MPC-HC) player from K-Lite instead of WMP. This player is superior to WMP. MPC-HC can play everything, and supports subtitles. We highly recommend using our MPC-HC.

Playback of HDR video

These are videos with a wider color range than normal.

First of all you need to use a player that supports HDR video. We recommend using MPC-HC player that is included with from K-Lite. WMP does not support HDR.

You also need to use a video renderer that supports HDR. The K-Lite Codec Pack contains two renderers that are compatible with HDR: MPC Video Renderer and madVR. You can choose the renderer that MPC-HC uses during installation of the codec pack, or here after install:
MPC-HC options > Playback > Output > Video Renderer

MPC Video Renderer is easier to use and works better with lower-end GPUs. MadVR has more advanced settings, but can be difficult to configure properly.

Playback of UltraHD HDR videos requires modern hardware, with a graphics card (GPU) that supports hardware accelered decoding of 10-bit HEVC video.

MPC Video Renderer also supports Dolby Vision (DoVi) (profiles 5/8.1/8.4 only).

If you are using madVR on Windows 11 and HDR fails to turn on properly, then that could be due to a bug in madVR. You should see devices getting duplicated in its settings when this is the cause. You can fix this by downloading the latest madVR test build (v205 or newer). Overwrite the madVR files installed by the codec pack. Besides this bug fix, the only difference in the test builds are extra HDR tonemapping settings (all experimental). The test build also expires after a few months. It shows a warning when you need to update it.

Solving audio problems

Audio isn't working in MPC-HC

Change the audio renderer:
MPC-HC options > Playback > Output

If volume is very low:

Codec Tweak Tool > Fixes > Reset Windows Audio Mixer volume
Codec Tweak Tool > Audio Output > "Windows Sound Settings" > Select correct speaker configuration
If voices are too quiet, then usually Stereo is correct choice, along with the boost center option.
MPC-HC options > Internal Filters > Audio Switcher > Enable "Normalize"

Solutions for stuttering, crackling, drop outs, and lip sync issues:

First check CPU usage during playback. Press Ctrl+Shift+Esc to open Windows Task Manager. If CPU usage is close to 100% then your computer might not be powerful enough to play high resolution videos. Visit our forum for advice.
Disable fast startup in Windows 10: Windows Control Panel > Power Options > "Choose what the power buttons do" > uncheck "Turn on fast startup"
Windows Control Panel > Sound > Speakers > Properties > Enhancements > Disable all sound effects
Windows Control Panel > Sound > Speakers > Properties > Advanced > disable the two "Exclusive mode" options
You should keep these options enabled if you want to bitstream audio to a receiver.
On laptops: Windows Control Panel > Power Options > select "High performance" power plan. If this works, then increasing the value of "Minimum processor state" in the other power plans may also solve it.
Update your sound driver. Many computers have Realtek audio chip: latest Realtek driver (use generic one). You can also use the generic "High Definition Audio Driver" from Microsoft.
Use Latency Monitor to check if you have any driver installed that cause high DPC latency. Such drivers should be replaced with a newer (or older) version.
If you have overclocked your CPU, then reset to stock speed and voltage settings, and test if that makes any difference.
If you have an Intel CPU, the use InSpectre tool to disable the Meltdown/Spectre protections. These have a negative impact on performance and increase latency. It does not matter much for security since most modern web browsers already provide protection against these processor flaws.
If you are running virtual machines using Hyper-V, then closing the VMs might solve audio stuttering.
Antivirus software can sometimes also cause DPC latency, for example when they monitor network activity. Try removing it and just use the built-in scanner from Windows 10.
Check if a BIOS update is available for your motherboard.

Graphics driver configuration tweaks

Fix stuttering or bad video playback performance with NVIDIA drivers

NVIDIA control panel > Manage 3D settings > Vertical Sync > On

NVIDIA control panel > Manage 3D settings > Global Settings > Power Management Mode > Select Adaptive (instead of the default value Optimal)

In some cases the Adaptive/Optimal choices are unavailable, and a Normal choice is used instead. You don't need to make any change in that situation.

Washed out video with AMD 5000 and 6000 series GPUs

Enable "Use Direct3D 11" in the settings of MPC Video Renderer.

Fix screen tearing and/or video stuttering with AMD drivers

You need to disable Enhanced Sync and Freesync in the AMD driver settings. Proper video playback requires a constant refresh rate. You can either disable these features globally in the driver settings, or you can create an application profile for MPC-HC and disable them there.

To add an application profile:
AMD settings > Gaming > Add > Browse > "C:\Program Files (x86)\K-Lite Codec Pack\MPC-HC64\mpc-hc64.exe"

Tips for MadVR

Video is black for a few seconds at start of playback

This may happen due to the Focus Assist feature of Windows 10 Build 1803. You can fix it by completely turning off Focus Assist, including its automatic rules.

Stuttering with NVIDIA RTX cards

madVR settings > rendering > exclusive mode > "how many frame shall be presented in advance" = 1

Make same change for windowed mode.

Also read the graphics driver tweaks above.

Report bugs!!!

It is really important that you reports any problems that you may have. The developers of the various codecs can only fix problems if they know they exist. Don't expect others to have the same problems as you. Bugs often only occur with specific combinations of player/settings/hardware/drivers, or only with specific files.

You can report bugs on our forum. The experts there will help diagnose your problem and can often provide you with a direct solution or forward the information to the developers if something needs to be fixed.

Submit your feature requests

If you got a suggestion then please submit it on our forum so we can give proper feedback. It often happens that the requested functionality is already available. We can teach you where to find those options.

File doesn't play?

Submit the details on our forum. We might be able to add support for that format in a future version. For example, if VLC is capable of playing the file, then we can usually make it work rather easily.