Fix NS_E_WMR_WAITINGONFORMATSWITCH (0XC00D105B) in Windows

Quick Fix (30 seconds) — Close and restart the offending app

What's actually happening here is that your app — usually a video player, screen recorder, or streaming app — requested a format switch (like going from 24-bit audio to 16-bit, or from 1080p to 4K), but the Media Foundation pipeline never finished the transition. It's stuck in a waiting state, and any subsequent format change request just gets the 0XC00D105B error.

• Close the app completely. Not just minimize — kill it via Task Manager if needed. Look for anything that uses video or audio: browsers with open YouTube tabs, OBS, VLC, Discord, Spotify.
• Wait 5 seconds, then reopen the app. The pipeline resets when the last client disconnects.
• If that fixes it, you're done. The pipeline just needed a clean restart.

This works because the Media Foundation pipeline is per-process. When the app exits, the pipeline tears down. No format switch waiting, no deadlock.

Moderate Fix (5 minutes) — Kill stuck mfpmp.exe and reset the service

If closing the app didn't work, the pipeline survived the app close (usually because a background system component like Windows Camera Frame Server or Windows Audio keeps a reference alive). The real fix is to kill the Media Foundation Protected Pipeline process directly.

1. Press Ctrl+Shift+Esc to open Task Manager.
2. Go to the Details tab.
3. Look for mfpmp.exe (Media Foundation Protected Pipeline). If you don't see it, check Show processes from all users.
4. Right-click it and select End task. Confirm if prompted.
5. Now restart the Windows Audio service:
   • Press Win+R, type services.msc, hit Enter.
   • Find Windows Audio, right-click, choose Restart.
6. Try your app again.

The reason step 3 works is that mfpmp.exe hosts the Media Foundation transform pipeline in a separate process. If it's stuck waiting on a format switch, no amount of restarting the app will help — the process holds the state. Killing it forces the pipeline to rebuild from scratch.

Restarting Windows Audio is overkill but necessary because some audio endpoints cache format negotiation data. If you skip it, you might still get the error on the first format change attempt.

Advanced Fix (15+ minutes) — Reset the entire Media Foundation stack via registry

If neither of the above works — and I've only seen this on machines with deeply corrupted media codec registrations after a bad driver update — you need to nuke the Media Foundation topology from the registry and re-register everything.

Warning: This will reset any third-party codec registrations (like K-Lite Codec Pack or CCCP). You'll need to reinstall them afterward.

1. Open an elevated Command Prompt: right-click Start, select Terminal (Admin) or Command Prompt (Admin).
2. Run these commands in order:

   reg delete "HKLM\SOFTWARE\Microsoft\Windows Media Foundation" /f
   reg delete "HKLM\SOFTWARE\Wow6432Node\Microsoft\Windows Media Foundation" /f
   reg delete "HKCU\SOFTWARE\Microsoft\Windows Media Foundation" /f
   reg delete "HKCU\SOFTWARE\Wow6432Node\Microsoft\Windows Media Foundation" /f
   

3. Now re-register the default Media Foundation components:

   cd %windir%\system32
   for %i in (*.dll) do regsvr32 /s %i 2>nul
   

4. Reboot your machine.

The reason this works is that the format switch negotiation is stored per-device in the registry under those keys. If a stale entry (left over from a codec pack uninstall or driver update) describes a format that no longer exists on your system, the pipeline will wait forever for the driver to confirm it can handle that format. Deleting those keys forces Windows to rediscover all supported formats fresh from the actual drivers.

One real-world scenario where this happens: you update your NVIDIA graphics driver, and the audio driver part of the HDMI/DP audio endpoint gets a new format list. The old registry key still says "supports 7.1 24/192" but the new driver only does 5.1 16/48. Any app trying to switch to that old format will hang on the switch and throw 0XC00D105B.

Still broken? Check these

• Third-party audio enhancements: Disable anything like Dolby Atmos, DTS Sound, or Nahimic in the sound control panel. They inject custom format handlers that sometimes don't wait for the pipeline to finish.
• Windows version: This error is far more common on Windows 10 22H2 and Windows 11 23H2 with KB5039212 installed. That update introduced a race condition in mfplat.dll. If you're on that build, roll back the update.
• Event Viewer: Check under Applications and Services Logs > Microsoft > Windows > Media Foundation for MFReadWrite warnings. They'll tell you which format negotiation failed (e.g., "Requested audio format 0x0001 not supported by sink").

If you're still stuck after all this, you're looking at a deeper problem — likely a corrupted mfplat.dll or mfsvr.dll. Run sfc /scannow in an admin terminal. If that finds nothing, do a repair install using the Windows 11 Installation Assistant. I've never had to go further than that for this specific error code.