Unreal Engine Issues

UE-203175

Startup Movies in Lyra Flicker and trigger ensure: "Only one system can use the SlateThread at the same time. GetMoviePlayer is not compatible with PreLoadScreen."

Startup Movies in Lyra Flicker and trigger ensure: "Only one system can use the SlateThread at the same time. GetMoviePlayer is not compatible with PreLoadScreen."

Description

When adding startup movies to Lyra, the movie playback flickers and an ensure conditions fails with the message:

Ensure condition failed: bSuccess  [File:D:\build\++UE5\Sync\Engine\Source\Runtime\MoviePlayer\Private\MoviePlayerThreading.cpp] [Line: 198] 
Only one system can use the SlateThread at the same time. GetMoviePlayer is not compatible with PreLoadScreen.

Found by internal tester, reproduced 3/3 while verifying [Link Removed].

A video is attached where the tester recorded the startup movie flickering, but the recording makes it look much less severe.

Steps to Reproduce
  1. Create a Lyra Sample project in 5.3
  2. Add a loading screen movie to the Content/Movies folder (LoadingScreen.mp4 from ShooterGame works well)
  3. Open up the project settings and add a startup movie pointing at the loading screen asset
  4. Package the build for windows
  5. Run LyraStarterGame.exe

Actual Result: Startup Movie flickers severely, and an ensure is generated

Expected Result: Video plays without flickering, and no ensure occurs

Callstack
=== Handled ensure: ===

Ensure condition failed: bSuccess  [File:D:\build\++UE5\Sync\Engine\Source\Runtime\MoviePlayer\Private\MoviePlayerThreading.cpp] [Line: 198] 
Only one system can use the SlateThread at the same time. GetMoviePlayer is not compatible with PreLoadScreen.
Stack: 
LyraGame.exe!FSlateLoadingThreadTask::Init() []
LyraGame.exe!FRunnableThreadWin::Run() []
LyraGame.exe!FRunnableThreadWin::GuardedRun() []
KERNEL32.DLL!UnknownFunction []
ntdll.dll!UnknownFunction []

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Unresolved
ComponentMedia Framework
Affects Versions5.3.2
Target Fix5.6
CreatedDec 20, 2023
UpdatedOct 9, 2024
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