Gstreamer 1.0 v4l2src with Python halts

gst0.10.py

# PyGST with Gst 0.10 works fine

import gst

pipe = gst.parse_launch("""v4l2src device=/dev/video0 !
       appsink sync=false max-buffers=1 drop=true name=sink emit-signals=true""")

sink = pipe.get_by_name('sink')
pipe.set_state(gst.STATE_PLAYING)

while True:
	print "Getting a buffer"
	buf = sink.emit('pull-buffer')
	print len(buf)
	

gst1.0.py

# gi with Gst 1.0 freezes after two or so frames

import gi
gi.require_version('Gst', '1.0')
from gi.repository import GObject, Gst

# This doesn't seem to make any difference
#GObject.threads_init()

Gst.init(None)

# This works
#pipe = Gst.parse_launch("""videotestsrc !
#        appsink sync=false max-buffers=1 drop=true name=sink emit-signals=true""")

# This halts after a few frames
pipe = Gst.parse_launch("""v4l2src device=/dev/video0 !
       appsink sync=false max-buffers=1 drop=true name=sink emit-signals=true""")

sink = pipe.get_by_name('sink')
pipe.set_state(Gst.State.PLAYING)

while True:
	print "Getting a sample"
	sample = sink.emit('pull-sample')
	print sample.get_buffer().get_size()