UE4 NDI ViewportCapture crash with post process

vnihouarn

New member
Hi,

I am using UE4.27 and the editor crashes if I assign a post process material to a NDI ViewportCapture. It happens with any post process material.

I make fulldome/planetarium projects. I use a SceneCaptureComponentCube and some materials to transform the result to a fulldome format. I want to make a NDI output of the result of those materials, so I thought I would use the result of my materials as a post process material for the NDI Viewport Capture.

The whole thing works for consistently around a minute before crashing and I get this crash report:

Unhandled Exception: EXCEPTION_ACCESS_VIOLATION 0x0000008c00000087

UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_NDIIO!UNDIViewportCaptureComponent::TickComponent() [C:\Users\nihou\OneDrive\Documents\Unreal Projects\NDI_Compile01\Plugins\NDIIO\Source\Core\Classes\Components\NDIViewportCaptureComponent.cpp:307]
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Core
UE4Editor_Core
UE4Editor_Core
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_Engine
UE4Editor_UnrealEd
UE4Editor_UnrealEd
UE4Editor
UE4Editor
UE4Editor
UE4Editor
UE4Editor
UE4Editor
kernel32
ntdll

I don’t really know what it means.

I compiled the NDI plugin for UE4.27 myself since it isn’t installed with NDI for UE4 (it only has a version up to UE4.26), but I don’t think that’s the problem since the same thing happens with UE4.26.

Does anybody has an idea of why that is happening or how to find a way to prevent that crash?

Or even an alternative to make a NDI capture of a material?

Any help would be appreciated.

Thanks in advance,

Vincent
 

Jarno

Post-LW Engineer
Check the memory usage. My first thought is that some per-frame resource is not being released.

---JvdL---
 

vnihouarn

New member
Check the memory usage. My first thought is that some per-frame resource is not being released.

---JvdL---
Thank you for your answer! It's nice to know someone read what I wrote. ;-)

I also think it's something related to memory usage but don't really know how to troubleshoot something like that.

I found a thread about a problem that looks really similar to mine:


It's really similar because if I do a garbage collect, the editor crashes (in any play mode) too.
It says:


Burmester said:
This seems to be related to Garbage Collection, if I manually trigger garbage collection when in Standalone Game mode, my NDI input immediately freezes.

It is related to the Render Thread EndFrame Delegate getting removed, even though the NDI Receiver does not get destroyed.
Registering a Lambda function calling the NDI Receiver instead of the UObject/member function fixes the issue.


Sadly, I don't know what this means. Do you understand it ?

Thanks again for your help
 

vnihouarn

New member
Today, I tried adding my post process material through a post process volume instead of specifying the post process in the NDI cine capture camera component. The result is the same: crash after a minute.

Is there no post process material support with the NDI for UE4 plugin?

Does anybody knows a way to "draw" the result of a material, through a render texture for example, on a camera view (the NDI cine camera ) that doesn't rely on the use of a post process material?

I thought of using UMG but I haven't found a way to add a widget to a camera view, only to the viewport. Anybody knows if there is a way to do this?
 

jritts

New member
Same issue here. Commenting out these lines in NDIViewportCaptureComponent.cpp works around the crash, but presumably disables post.

// Start performing post processing
View->StartFinalPostprocessSettings(ViewInfo.Location);
// Override the Post Process Setting given the view info
View->OverridePostProcessSettings(ViewInfo.PostProcessSettings, ViewInfo.PostProcessBlendWeight);
// Finalize the view settings
View->EndFinalPostprocessSettings(ViewInitOptions);
 
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