Setting a special pixel aspect ratio results in viewer letterboxing instead of stretching of the video
Submitted by Jeff F.T.
Assigned to Thibault Saunier
Continuation of bug T2880.
Since the port to GStreamer 1.x/GI, when you set a special aspect ratio in the project settings, the image provided by gstreamer doesn't stretch to fill the viewer's AspectFrame: it uses letterboxing instead.
This affects rendering as well as live playback.
Imported from https://bugzilla.gnome.org/show_bug.cgi?id=720702