v4l2src returns different caps from its get_caps() function every time I call it.. 

When its called when the pipeline is running, it returns caps that are incompatible with the ones it called setcaps() with. It should at least cache those and return them unioned with whatever else it has. Or maybe the FIXME should be fixed in get_caps()..


Small python program that shows the problem with my Logitech Quickcam Fusion (where 15/1 is not an acceptable framerate once the device has been opened):

import gst,time

pipeline = gst.parse_launch ("v4l2src ! ffmpegcolorspace ! videoscale ! video/x-raw-yuv,framerate=(fraction)15/1,width=352, height=288, format=(fourcc)I420 ! identity name=i ! ffmpegcolorspace ! videoscale ! xvimagesink sync=false")

pipeline.set_state(gst.STATE_PLAYING);

time.sleep(1)

i = pipeline.get_by_name("i")

print i.get_pad("src").get_caps().to_string()

pipeline.set_state(gst.STATE_NULL);