[Bug]: Failed to initialize Media Foundation encoder - MP4 recording fails on Windows 10 with AMD GPU (hr=0x80070003)

[Peisr25]

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Describe the bug

When attempting to record the screen, OpenScreen fails with the following error:

"Failed to load MP4 create in WriteFromURL failed (hr=0x80070003) ERROR: Failed to initialize Media Foundation encoder"

Diagnostic details:

• The Media Foundation feature (MediaPlayback) is Enabled on the system
• Windows Media Player is Enabled
• sfc /scannow completed successfully with no system file corruption found
• Media Foundation DLLs exist: mf.dll, mfplat.dll, mfreadwrite.dll, msmpeg2vdec.dll, msmpeg2adec.dll are all present
• The Windows registry keys for H.264 encoder registration are empty:
  • HKLM:\SOFTWARE\Microsoft\Windows Media Foundation\HardwareMFT — no entries found
  • HKLM:\SOFTWARE\Classes\MediaFoundation\Transforms — no H.264/encoder entries found
• All DLLs were re-registered with regsvr32 /s without errors, but the registry keys remain empty
• The error code 0x80070003 (ERROR_PATH_NOT_FOUND) suggests the application cannot locate the required encoder MFT (Media Foundation Transform)

Expected behavior

OpenScreen should successfully initialize the Media Foundation H.264 encoder and record the screen to MP4 format without errors.

To Reproduce

1. Install OpenScreen on Windows 10 Home (Build 19041) with AMD Radeon RX 7700 XT
2. Open OpenScreen
3. Click "Record" or attempt to start a screen recording
4. See the error: "Failed to load MP4 create in WriteFromURL failed (hr=0x80070003) ERROR: Failed to initialize Media Foundation encoder"

Screenshots

OS

Windows

OS Version

Windows 10 Home (Core) — Build 19041 (20H2), Servicing Stack 10.0.19041.7402 Last cumulative update: KB5094127 (2026-06-13)

Other OS

No response

Browser

None

Browser Version

No response

Other Browser

No response

Device Type

Desktop

Other Device

No response

Additional context

Full system environment:

• CPU/GPU: AMD Radeon RX 7700 XT (Driver: 32.0.31019.2002, Status: OK)
• Windows Edition: Home (Core) — NOT an N/KN edition, so Media Feature Pack is not the issue
• MediaPlayback optional feature: Enabled
• WindowsMediaPlayer optional feature: Enabled
• System File Checker (sfc /scannow): Completed successfully, no integrity violations
• DISM RestoreHealth: Not yet attempted

Registry check results (all empty):

• HKLM:\SOFTWARE\Microsoft\Windows Media Foundation\HardwareMFT — No subkeys
• HKLM:\SOFTWARE\Classes\MediaFoundation\Transforms matching h264/enc — No entries

Possible root cause:
The H.264 Media Foundation Transform (MFT) encoder does not appear to be registered on this system, even though all required DLLs are present and the Media Foundation features are enabled. OpenScreen may need a fallback software encoder, or may need to explicitly register/enumerate available MFTs before attempting to create the MP4 writer.

Workaround attempted:

• Manually registered msmpeg2venc.dll and mfh264enc.dll via regsvr32 /s — did not resolve the issue
• Ran OpenScreen as Administrator — same error

[github-actions]

Fixed by #20 and merged into main.

This change is assigned to the Next Release release milestone and is not necessarily available in the latest downloadable desktop release yet. It is currently marked as status: pending release until a packaged release containing it is published.

[EtienneLescot]

Moved into v1.5.1 as part of the pre-release cut.