[UMF, 4.7.5] MediaPlayer->Close() is not exposed to Blueprint

Development Programming & Scripting
1

The UMF MediaPlayer has OnMediaOpened and OnMediaClosed delegates, but there is no Close() command available to Blueprint. We solved this locally by creating a static function (globally available in blueprint) with the following lines of code:

if (IsValid(Player))
{
TSharedPtr IPlayer = Player->GetPlayer();

	IPlayer->Close();
}

Works like a charm.

2

Thanks, I will make this change in the Master branch right after our 4.8 branch is complete. This will then be available in 4.9.

UPDATE
This is now checked in (GitHub commit)

3

Oh, while I remember! I noticed that doing this Close() call on a player that has not opened a URL, or is not playing yet, may crash the device. So an additional check on the player may be needed. Thanks gmpreussner!

4

Oh, that’s not good - Close() should never crash. On which platform did this happen? Windows?

Do you have a callstack or log file?

5

This is on Android, not tested on iOS. There are several other UMF problems on mobile, probably related to JNI.

I did not fetch any logs when it happened as I only focused on not getting the crash. I only remembered seeing something related to closing the media player in the stack trace and I remembered I put a Close() on initializing the player. There’s a small problem on PC where the video may continue to play in the editor and it messes with the regular playback.

I had that close just to make sure the media was “reset” on PIE. Then it crashed on device so I had to remove it.

6

Hi again gmpreussner. Sorry for the delay. I just tried to reproduce the problem, to give you logs, and I found out two specific details that are needed to get it to crash.

  1. The MediaPlayer must start / be saved with an empty URL.
  2. The Close() command must accidentally run via the Tick function. Directly or through a function later down the line.

When these conditions are met, even if the Close() is only run once, it will crash on play or on start. It’s a very specific scenario for it to crash.

I think that I accidentally had the Close() and the Play() executing close to each other and causing some conflict. The log is attached below, which doesn’t say much, but I think I essentially did the worst thing I could do with the MediaPlayer.

I did not test this on the device, but I’m certain it is related to a MediaPlayer that starts with an empty URL rather than a default existing video.

VisualStudio crash callstack

7

Your callstack seems to be ending inside your own code. Are you able to see this crash in the Visual Studio debugger?

8

Sorry gmpreussner, I was stupid enough to not check if the IPlayer is valid. The crash was because I got a null pointer. (it’s the same code as in the original post)

Thanks for implementing the Close() function!