I have prepared two videos to show the problem. While with a real drone the aspect ratio of the incoming streamed video is always correct, independent of whether camera mode or video mode is chosen, it is not with the Sphinx. In camera mode, even though the video reports to be 1024x768, it is seemingly not, since the aspect ratio is not correct. I suppose it is still 1280x720, because I can work with it perfectly if I downscale to 640x360 instead of 512x384. Also the aspect ratio is correct then.
OK video with real drone:
Problematic video with Sphinx: