did not try it yet, but sounds good!
Linux Screensharing in Google Hangouts

1. Get https://github.com/umlaeute/v4l2loopback
2. Build and load module (use modprobe v4l2loobpack debug=(1|2) for testing)
3. Compile yuv4mpeg_to_v4l2.c from experimental branch
4. mkfifo pipe
5. ./yuv4mpeg_to_v4l2 < pipe
6. cvlc --vout=yuv --yuv-yuv4mpeg2 --yuv-chroma=I420 --yuv-file=pipe screen:// --screen-width 640 --screen-height 360 --screen-fps 3 --screen-caching 200 --screen-top 75
7. ???
8. PROFIT =)

Play with transcode to get a higher cutout.
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