Solved Crash when deleteLater() QML Video component in Qt 5.12.4-5.13.1, but not in Qt.5.12.3

[ChrisTof]

I create QML video component from within C++

QQmlComponent component(qmlEngine, QUrl::fromLocalFile("Video.qml"));
QQmlContext* rootItemContext = QQmlEngine::contextForObject(rootWindow);
QQuickItem *video= qobject_cast<QQuickItem*>(component.beginCreate(rootItemContext));
if(video != nullptr) {
   QQmlEngine::setObjectOwnership(video, QQmlEngine::CppOwnership);
   video->setParentItem(rootWindow->contentItem());
   video->setParent(qmlEngine);
   // set video properties...
}
component.completeCreate();

video.qml is simple:

import QtQuick 2.0
import QtMultimedia 5.13

Video {
    id: video

    source: "video.mp4"
    width: 800
    height: 400
    x: 0
    y: 0
    autoPlay: 1
}

I remove the video later:

video->deleteLater();

It works exactly as I expect in Qt 5.12.3. But in Qt 5.13 the application crashes.
I can see in Event Viewer that the problem is with Qt5Muldimedia.dll

Faulting application name: app.exe, version: 0.0.0.0, time stamp: 0x5d0a9f7a
Faulting module name: Qt5Multimedia.dll, version: 5.13.0.0, time stamp: 0x5d027ea9
Exception code: 0xc0000005
Fault offset: 0x000000000004e740
Faulting process id: 0xc4c
Faulting application start time: 0x01d53c821dd1a2fd
Faulting application path: C:\Program Files\app\bin\app.exe
Faulting module path: C:\Program Files\qml\qt\Qt5Multimedia.dll
Faulting package full name: 
Faulting package-relative application ID: 

Fault bucket 2258054399709010408, type 4
Event Name: APPCRASH
Response: Not available
Cab Id: 0

Problem signature:
P1: app.exe
P2: 0.0.0.0
P3: 5d0a9f7a
P4: Qt5Multimedia.dll
P5: 5.13.0.0
P6: 5d027ea9
P7: c0000005
P8: 000000000004e740
P9: 
P10: 

I wonder whether the way I remove the video component is wrong or there is a bug in Qt 5.13?
How can I investigate more what really happens there?
I also add that I remove video component when it is playing, but stopping before delete does not change anything.

[ChrisTof]

Fix will be introduced in 5.13.2 and 5.14.0 Alpha.
If you do not want to wait, you can make needed changes to the source code and built it yourself.
In file: src/plugins/common/evr/evrcustompresenter.cpp change line 1146 from

if (m_renderState == RenderStopped && m_surface->isActive()) {

to:

if (m_renderState == RenderStopped && m_surface && m_surface->isActive()) {

See issue for more information.

[jsulm]

@ChrisTof said in Crash when deleteLater() QML Video component in Qt 5.13, but not in Qt.5.12.3:

How can I investigate more what really happens there?

Run through debugger and take a look at stack trace after the crash

[ChrisTof]

For some reason I can debug Qt 5.12.3, but when I try to run debug on 5.13 then:

Unable to create a debugging engine.

I have already added 'Debugging Tools for Windows'.

[jsulm]

@christof And the correct debugger is set in the Kit?

[ChrisTof]

It wasn't. Got the debugger working.

The image was taken during debugging 5.13.0.
The same code executed under 5.12.3 runs without any error.

[ChrisTof]

In Qt 5.13.1 the error still persists. Any ideas why that happens?

[g3nx]

I'm facing a similar issue but with pure QML code. The application crashes just after removing the QML Component containing the video item. Problem persists both in qt 5.12.4 and qt 5.13.1

[g3nx]

Furthermore i can confirm that also in my case, the code works properly with qt 5.12.3. It does seem a regression introduced from qt 5.12.4.
@ChrisTof could you confirm that the problem persist in qt 5.12.4 also in your case?

[ChrisTof]

Yes, I can confirm the problem persists in qt 5.12.4.
I reported the issue: https://bugreports.qt.io/browse/QTBUG-78207

[ChrisTof]

Fix will be introduced in 5.13.2 and 5.14.0 Alpha.
If you do not want to wait, you can make needed changes to the source code and built it yourself.
In file: src/plugins/common/evr/evrcustompresenter.cpp change line 1146 from

if (m_renderState == RenderStopped && m_surface->isActive()) {

to:

if (m_renderState == RenderStopped && m_surface && m_surface->isActive()) {

See issue for more information.