Setting gstreamer element properties at runtime

rpicamsrc_propset.py

#!/usr/bin/python3

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

def bus_call(bus, msg, *args):
    #print("BUSCALL", msg, msg.type, *args)
    if msg.type == Gst.MessageType.EOS:
        print("End-of-stream")
        loop.quit()
        return
    elif msg.type == Gst.MessageType.ERROR:
        print("GST ERROR", msg.parse_error())
        loop.quit()
        return
    return True

saturation = -100
def set_saturation():
    global saturation
    saturation += 10
    print("Setting saturation to {0}".format(saturation))
    videosrc.set_property("saturation", saturation)
    return True


if __name__ == "__main__":
    GObject.threads_init()
    # initialization
    loop = GObject.MainLoop()
    Gst.init(None)
    # create elements
    pipeline = Gst.Pipeline()
    # watch for messages on the pipeline's bus (note that this will only
    # work like this when a GLib main loop is running)
    bus = pipeline.get_bus()
    bus.add_watch(0, bus_call, loop) # 0 == GLib.PRIORITY_DEFAULT 

    # create elements
    videosrc = Gst.ElementFactory.make('v4l2src', "src0")
    #videosrc = Gst.ElementFactory.make('rpicamsrc', "src0")
    videosrc.set_property("saturation", saturation)

    sink = Gst.ElementFactory.make("autovideosink", 'sink0')

    caps = Gst.Caps.from_string("video/x-raw, width=320, height=240")

    # add elements
    pipeline.add(videosrc)
    pipeline.add(sink)

    # link elements 
    videosrc.link_filtered(sink, caps)    

    # this will call set_saturation every 1s
    GObject.timeout_add(1000, set_saturation)

    # run
    pipeline.set_state(Gst.State.PLAYING)
    try:
        loop.run()
    except Exception as e:
        print(e)
    # cleanup
    pipeline.set_state(Gst.State.NULL)

videosrc = Gst.ElementFactory.make('v4l2src', "src0")

How does one specify a given 'v4l2src' device? Assuming one has two camera devices on /dev/video0 and /dev/video1.

I think it's videosrc.set_property("device", "/dev/video1")

See the command gst-inspect-1.0 v4l2src for details