Engine crash on opening WebM video

Hey,

Anyone around here who managed to get WebM runing for Ue 5.1 on Windows?
I have tried it, and as soon as I open the file in the Media PLayer, the Engine crashes.
Same when I try to open it during gameplay.
Unreal Engine 5.1
WebM VP9 .

Hey there @strezoiu! May I see the callstack from the crash?

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Unhandled Exception: EXCEPTION_ACCESS_VIOLATION writing address 0x00007ffbc9e55f30

UnrealEditor_SlateCore!SWidget::RegisterActiveTimer() [D:\build++UE5\Sync\Engine\Source\Runtime\SlateCore\Private\Widgets\SWidget.cpp:1777]
UnrealEditor_Slate!STableViewBase::RequestLayoutRefresh() [D:\build++UE5\Sync\Engine\Source\Runtime\Slate\Private\Widgets\Views\STableViewBase.cpp:1063]
UnrealEditor_MediaPlayerEditor!TBaseSPMethodDelegateInstance<0,SMediaPlayerEditorPlaylist,1,void __cdecl(enum EMediaEvent),FDefaultDelegateUserPolicy>::ExecuteIfSafe() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:312]
UnrealEditor_MediaAssets!UMediaPlayer::HandlePlayerMediaEvent() [D:\build++UE5\Sync\Engine\Source\Runtime\MediaAssets\Private\Assets\MediaPlayer.cpp:938]
UnrealEditor_MediaAssets!TBaseUObjectMethodDelegateInstance<0,UMediaPlayer,void __cdecl(enum EMediaEvent),FDefaultDelegateUserPolicy>::ExecuteIfSafe() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\DelegateInstancesImpl.h:618]
UnrealEditor_MediaUtils!TMulticastDelegateBase::Broadcast<IBaseDelegateInstance<void __cdecl(enum EMediaEvent),FDefaultDelegateUserPolicy>,TDelegate<void __cdecl(enum EMediaEvent),FDefaultDelegateUserPolicy>,enum EMediaEvent>() [D:\build++UE5\Sync\Engine\Source\Runtime\Core\Public\Delegates\MulticastDelegateBase.h:178]
UnrealEditor_MediaUtils!FMediaPlayerFacade::ProcessEvent() [D:\build++UE5\Sync\Engine\Source\Runtime\MediaUtils\Private\MediaPlayerFacade.cpp:1836]
UnrealEditor_MediaUtils!FMediaPlayerFacade::TickFetch() [D:\build++UE5\Sync\Engine\Source\Runtime\MediaUtils\Private\MediaPlayerFacade.cpp:2060]
UnrealEditor_Media!FMediaClock::TickFetch() [D:\build++UE5\Sync\Engine\Source\Runtime\Media\Private\MediaClock.cpp:33]
UnrealEditor_Media!FMediaModule::TickPostEngine() [D:\build++UE5\Sync\Engine\Source\Runtime\Media\Private\MediaModule.cpp:150]
UnrealEditor_UnrealEd!UEditorEngine::Tick() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\EditorEngine.cpp:1949]
UnrealEditor_UnrealEd!UUnrealEdEngine::Tick() [D:\build++UE5\Sync\Engine\Source\Editor\UnrealEd\Private\UnrealEdEngine.cpp:517]
UnrealEditor!FEngineLoop::Tick() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\LaunchEngineLoop.cpp:5369]
UnrealEditor!GuardedMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Launch.cpp:202]
UnrealEditor!GuardedMainWrapper() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:107]
UnrealEditor!LaunchWindowsStartup() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:244]
UnrealEditor!WinMain() [D:\build++UE5\Sync\Engine\Source\Runtime\Launch\Private\Windows\LaunchWindows.cpp:282]
UnrealEditor!__scrt_common_main_seh() [D:\a_work\1\s\src\vctools\crt\vcstartup\src\startup\exe_common.inl:288]
kernel32
ntdll

I also tried WebM VP 8, same result

I can confirm it’s not just you on 5.1, it seems like there was a bug specifically in 5.1 that had been corrected by 5.3. I was unable to locate the specific PR for it however.

■■■■…
OK,
Thank you!!!

I believe I found the PR that fixed this!

https://github.com/EpicGames/UnrealEngine/pull/9810

If you use source builds you may be able to splice this in without updating your project to 5.3.