There is new trend in video coding:
http://figmentos.iblogger.org/10bit-encoding/

So please maybe you can add 10bit support to gstreamer.
Google says gstreamer may be recompiled with new keys.
Screenshot:
http://dl.dropbox.com/u/9476941/10-bit.png

Test files:
http://www.cccp-project.net/beta/test_files/H.264-10bit-sample-railgun.mkv
http://dl.dropbox.com/u/9476941/10-bit_h264-sample.mkv

These links threads may help:
http://bugzilla.libav.org/show_bug.cgi?id=104
https://bugzilla.gnome.org/show_bug.cgi?id=665034

I think this decoding feature may be very useful nowadays.
Thankyou.