Memory leak using QtMultimedia GStreamer plugin with d3d11h265dec decoder on Windows

I noticed a memory leak on Windows when playing h265 videos through QtMultimedia with the Gstreamer plugin.

The version of Gstreamer used (64bit): https://gstreamer.freedesktop.org/data/pkg/windows/1.18.5/msvc/

Qt 5.15.1 was built from sources using the following command:

configure.bat -mp -opengl dynamic -gstreamer 1.0 -prefix C:\Users\ab\qt515-x64 -release -opensource -confirm-license -L C:\gstreamer\1.0\msvc_x86_64\lib -I C:\gstreamer\1.0\msvc_x86_64\include\gstreamer-1.0 -I C:\gstreamer\1.0\msvc_x86_64\include\gstreamer-1.0\gst -I C:\gstreamer\1.0\msvc_x86_64\include -I C:\gstreamer\1.0\msvc_x86_64\include\glib-2.0 -I C:\gstreamer\1.0\msvc_x86_64\lib\glib-2.0\include -I C:\gstreamer\1.0\msvc_x86_64\lib\gstreamer-1.0\include -recheck-all

The compiler used was: Microsoft Visual C++ Compiler 16.11.31729.503 (amd64)

I have attached a sample project to easily reproduce the issue.

Note that when main.cpp:36 is commented out, the memory leak disappears. This implies that the leak is related to the use of the d3d11h265dec decoder.