im scratching my head for a while, tried a few pipelines,

i tried implementing scaling as a python gstreamer filter (I got amazing 1 fps).
If i drop zooming theora may work, but it has many drawbacks like cpu load and some lags and some missing options. Perhaps I manage to get a version without zooming.
But next thing to look at is how gstreamer1.0 works and i may also try the ffvideoscale plugin.