video support? webm/mp4/mkv - vp8-9/h264/h265 - ffmpeg?
Any chance for video support? To support playback of WebM files for example which normally is small and on a loop makes perfect sense as it replaced gif. Many that release WebM loops also release these in mp4 or avi aswell technically for the higher quality.
This feature would be geared towards the imageboard users that user 4chan and the like and boorus like gelbooru/danbooru.
If audio playback is also done then you should have a global mute button that is also saved between sessions (in your settings for example) Allowing users to keep things muted if they want, no matter when or how they open it.
Most of this can be done by grabbing ffmpeg and hooking it in. That would technically allow you for more support for other formats and codecs, but the main ones are listed above. (atleast till AV1 gets mainstream)
I guess QtMultimedia should be able to handle it all by itself aswell: https://doc.qt.io/qt-5/qtmultimedia-multimediawidgets-player-example.html