From documentation(http://doc.qt.io/qt-5/qabstractvideofilter.html), it's not clear who must to delete pointer to QVideoFilterRunnable created in createFilterRunnable().

According documentation:

Once created, QVideoFilterRunnable instances are managed by Qt Multimedia and will be automatically destroyed and recreated when necessary, for example when the scene graph is invalidated or the QQuickWindow changes or is closed.

But destructor of custom filter runnable doesn't called when application close. In attachments project with example of problem.