Current qt5 multimedia has a special video node for imx6 at "/src/plugins/videonode/imx6" which uses GPU DirectVIV to accelerate the video rendering.
So the rendering performance is almost same as the glimagesink. For check the free run frame rate, the qt multimedia source need change a little bit to set sink sync as false and calculate the real video rendering rate.
Set sync as false:
This is a widget application, not a QML application. It use QAudioRecorder as its background worker. By default it will use pulsesrc and lamemp3enc to recorder audio as mkv file at user home folder with name of clip_0001.mkv, clip_0002.mkv, and so on.
If need special pipeline for recording, example use imxmp3enc to record mp3 files, we need change the function GstElement *QGstreamerCaptureSession::buildEncodeBin in “src/plugins/gstreamer/mediacapture/qgstreamercapturesession.cpp” as well as QGstreamerMediaContainerControl(QObject *parent) in “src/plugins/gstreamer/mediacapture/qgstreamermediacontainercontrol.cpp”