Media Source BP crashes engine (REPRODUCABLE)

Development Programming & Scripting Blueprint
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So here’s a bug which can be reproduced in UE4.17.1.

I found this out because I wanted to create a TV screen which opens a video file on BeginPlay. It worked, until I went fullscreen using F11 (may not crash the first time).

Here’s how to reproduce the bug:

(As a precaution, when I made a blank project, I hit play and then hit F11 ten times to make sure the crash wasn’t occurring straight away).

  1. Open a blank project.
  2. Drop your video file into the content folder.
  3. Create a media player asset and media texture.
  4. Create a material and drag the Media Texture in there, connect it up to either base color or emissive color, and hit save/apply.
  5. Create an actor BP.
  6. Create an object inside the BP which the video created earlier will be viewed on (plane).
  7. Drop your material onto that object.
  8. Create two variables. One will have a type “Media Player” and the other will be a “Media Source”.
  9. Hit compile and set these variables to the media player and source of your video.
  10. In the BP Event Graph, add a getter for each of your two variables.
  11. drag off of the Media Player getter and add an “Open Source” node.
  12. Connect the node to your ‘BeginPlay’ event.
  13. Connect the Media Source getter to the Media Source input on the ‘Open Source’ node.
  14. Compile and save the BP and drag it into your world. The object should be black.
  15. Hit ‘Play (in editor)’. At this point, your video should be playing on the object you put into your BP.
  16. Finally, hit F11 until the editor freezes and crashes (You do not have to rapidly hit the button) (should take less than 10x F11’s. Usually happens on the first 4 tries).

I hope this bug gets fixed in the next update; I heard someone was having a similar problem in 4.16.