sdlvideosink is just completely busted suddenly and I don't know why - it was certainly working when I did the last commit to it. 

Need to investigate - this bug is to remind me to do so.

GST_DEBUG=sdl*:5,basesink:5 gst-launch videotestsrc ! video/x-raw-yuv,format='(fourcc)'I420 ! sdlvideosink
Setting pipeline to PAUSED ...
DEBUG (0x80509d8 - 0:00:01.446933000)             basesink(18409) gstbasesink.c(1731):gst_base_sink_change_state:<sdlvideosink0> READY to PAUSED, need preroll
DEBUG (0x80509d8 - 0:00:01.447250000)             basesink(18409) gstbasesink.c(1436):gst_base_sink_activate:<sdlvideosink0> Trying pull mode first
DEBUG (0x80509d8 - 0:00:01.447410000)             basesink(18409) gstbasesink.c(1445):gst_base_sink_activate:<sdlvideosink0> Falling back to push mode
DEBUG (0x80509d8 - 0:00:01.447561000)             basesink(18409) gstbasesink.c(1447):gst_base_sink_activate:<sdlvideosink0> Success activating push mode
DEBUG (0x80509d8 - 0:00:01.454279000)             basesink(18409) gstbasesink.c(1089):gst_base_sink_event:<sdlvideosink0> event 0x808a4a0
DEBUG (0x80509d8 - 0:00:01.454473000)             basesink(18409) gstbasesink.c(486):gst_base_sink_configure_segment:<sdlvideosink0> configured NEWSEGMENT 0:00:00.000000000 -- 5124095:34:33.709551615, time 0:00:00.000000000, accum 0:00:00.000000000
DEBUG (0x80509d8 - 0:00:01.454647000)             basesink(18409) gstbasesink.c(992):gst_base_sink_queue_object_unlocked:<sdlvideosink0> now 0 prerolled items
DEBUG (0x80509d8 - 0:00:01.454794000)             basesink(18409) gstbasesink.c(1040):gst_base_sink_queue_object_unlocked:<sdlvideosink0> need more preroll data 0 <= 0
Pipeline is PREROLLING ...
DEBUG (0x816ebf0 - 0:00:01.657396000)                  sdl(18409) sdlvideosink.c(684):gst_sdlvideosink_create: Using a 320x240 32bpp SDL screen with a 320x240 'YV12' YUV overlay
DEBUG (0x816ebf0 - 0:00:01.657675000)                  sdl(18409) sdlvideosink.c(694):gst_sdlvideosink_create: sdlvideosink: set to fourcc (YV12)
DEBUG (0x816ebf0 - 0:00:01.657934000)             basesink(18409) gstbasesink.c(1257):gst_base_sink_chain_unlocked:<sdlvideosink0> got times start: 0:00:00.000000000, end: 0:00:00.033333333
DEBUG (0x816ebf0 - 0:00:01.658095000)             basesink(18409) gstbasesink.c(992):gst_base_sink_queue_object_unlocked:<sdlvideosink0> now 1 prerolled items
DEBUG (0x816ebf0 - 0:00:01.658241000)             basesink(18409) gstbasesink.c(931):gst_base_sink_preroll_object:<sdlvideosink0> do preroll 0x816d298
DEBUG (0x816ebf0 - 0:00:01.658385000)             basesink(18409) gstbasesink.c(939):gst_base_sink_preroll_object:<sdlvideosink0> preroll buffer 0:00:00.000000000
X Error of failed request:  BadMatch (invalid parameter attributes)
  Major opcode of failed request:  141 (XVideo)
  Minor opcode of failed request:  19 ()
  Serial number of failed request:  24
  Current serial number in output stream:  25