roberto@jeremy:~$ gst-launch-0.10 -v v4l2src ! video/x-raw-yuv,format=\(fourcc\)UYVY,width=640,height=480 ! ffmpegcolorspace ! fakesink 
Setting pipeline to PAUSED ...
ERROR: Pipeline doesn't want to pause.
ERROR: from element /pipeline0/v4l2src0: Could not negotiate format
Additional debug info:
gstbasesrc.c(2056): gst_base_src_start (): /pipeline0/v4l2src0:
Check your filtered caps, if any
Setting pipeline to NULL ...
FREEING pipeline ...