roberto@jeremy:~$ cat gst.log 
0:00:00.128835000 10271 0x804e050 DEBUG              v4l2src gstv4l2src.c:582:gst_v4l2src_v4l2fourcc_to_structure: Unknown fourcc 0x30313953 S910
0:00:00.129030000 10271 0x804e050 DEBUG              v4l2src gstv4l2src.c:582:gst_v4l2src_v4l2fourcc_to_structure: Unknown fourcc 0x31435750 PWC1
0:00:00.129046000 10271 0x804e050 DEBUG              v4l2src gstv4l2src.c:582:gst_v4l2src_v4l2fourcc_to_structure: Unknown fourcc 0x32435750 PWC2
0:00:00.129655000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:383:gst_base_src_init:<GstBaseSrc@0x8113190> creating src pad
0:00:00.129752000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:386:gst_base_src_init:<GstBaseSrc@0x8113190> setting functions on src pad
0:00:00.129779000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:405:gst_base_src_init:<GstBaseSrc@0x8113190> adding src pad
0:00:00.129801000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:416:gst_base_src_init:<GstBaseSrc@0x8113190> init done
Setting pipeline to PAUSED ...
0:00:00.140667000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2116:gst_base_src_activate_push:<v4l2src0> Activating in push mode
0:00:00.140691000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:1977:gst_base_src_start:<v4l2src0> starting source
0:00:00.143586000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2014:gst_base_src_start:<v4l2src0> format: 3, have size: 1, size: 18446744073709551615, duration: -1
0:00:00.143611000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2022:gst_base_src_start:<v4l2src0> is seekable: 0
0:00:00.143625000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2028:gst_base_src_start:<v4l2src0> is random_access: 0
0:00:00.143651000 10271 0x804e050 DEBUG              v4l2src v4l2src_calls.c:362:gst_v4l2src_fill_format_list:<v4l2src0> getting src format enumerations
0:00:00.143669000 10271 0x804e050 DEBUG              v4l2src v4l2src_calls.c:377:gst_v4l2src_fill_format_list:<v4l2src0> got format UYVY
0:00:00.143818000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:1896:gst_base_src_default_negotiate:<v4l2src0> caps of src: video/x-raw-yuv, format=(fourcc)UYVY, width=(int)640, height=(int)480, framerate=(int){  }; video/x-raw-yuv, format=(fourcc)UYVY, width=(int)352, height=(int)288, framerate=(int){  }; video/x-raw-yuv, format=(fourcc)UYVY, width=(int)320, height=(int)240, framerate=(int){  }
0:00:00.165777000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:1903:gst_base_src_default_negotiate:<v4l2src0> caps of peer: video/x-raw-yuv, width=(int)640, height=(int)480, framerate=(fraction)[ 0/1, 2147483647/1 ], format=(fourcc)UYVY
0:00:00.165856000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:1909:gst_base_src_default_negotiate:<v4l2src0> intersect: EMPTY
0:00:00.165876000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2054:gst_base_src_start:<v4l2src0> could not negotiate, stopping
0:00:00.165891000 10271 0x804e050 WARN               basesrc gstbasesrc.c:2056:gst_base_src_start:<v4l2src0> error: Could not negotiate format
0:00:00.165904000 10271 0x804e050 WARN               basesrc gstbasesrc.c:2056:gst_base_src_start:<v4l2src0> error: Check your filtered caps, if any
0:00:00.165971000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2072:gst_base_src_stop:<v4l2src0> stopping source
0:00:00.166003000 10271 0x804e050 WARN               basesrc gstbasesrc.c:2160:gst_base_src_activate_push:<v4l2src0> Failed to start in push mode
0:00:00.166022000 10271 0x804e050 DEBUG              basesrc gstbasesrc.c:2319:gst_base_src_change_state:<v4l2src0> parent failed state change
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 ...