The default video display size for movies (without having ffmpeg available as far as I read about it) is 200x200 pixels, which is awefully small, doesn't seem to be configurable anywhere and is a square instead of 4:3 or anything else "reasonable". (no offense)
As every "normal" video recorded is either 4:3 or 16:9 and will "never" be a square (imagine a 16:9 video distorted to a square, that's nearly unwatchable compared to 4:3 distortion) I would recommend using at least a 4:3 aspect ratio as default, so that not all videos get distorted by default. Furthermore I'd recommend using a reasonable standard size such as 320x240 instead of 200x200 for aspect ratio reasons (see above) and size reasons (200 is really small)
One could think about using 640x480, too. 320x240 is the defacto standard minimum in my eyes.
Nice to have but not required would be a possibility to switch between a pre-defined 4:3 size and a pre-defined 16:9 size, which the user can choose from (as many digital cameras already shoot 16:9 videos). This feature might be added later, but the one above should urgently make it in the final release of gallery3.
this tracker is ONLY FOR GALLERY 2. Please file Gallery 3 items at http://apps.sourceforge.net/trac/gallery/