rpicamsrc: Add dynamic properties example

Python example of adjusting saturation on the fly

tests/examples/rpicamsrc/dynamicprops.py

@@ -0,0 +1,68 @@
+#!/usr/bin/python3
+
+import sys
+import gi
+gi.require_version('Gst', '1.0')
+from gi.repository import GObject, Gst
+
+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(pipeline):
+    global saturation
+    if saturation <= 100:
+      print("Setting saturation to {0}".format(saturation))
+      videosrc.set_property("saturation", saturation)
+      videosrc.set_property("annotation-text", "Saturation %d" % (saturation))
+    else:
+      pipeline.send_event (Gst.Event.new_eos())
+      return False
+    saturation += 10
+    return True
+
+
+if __name__ == "__main__":
+    GObject.threads_init()
+    # initialization
+    loop = GObject.MainLoop()
+    Gst.init(None)
+
+    pipeline = Gst.parse_launch ("rpicamsrc name=src ! video/x-h264,width=320,height=240 ! h264parse ! mp4mux ! filesink name=s")
+    if pipeline == None:
+      print ("Failed to create pipeline")
+      sys.exit(0)
+
+    # 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)
+
+    videosrc = pipeline.get_by_name ("src")
+    videosrc.set_property("saturation", saturation)
+    videosrc.set_property("annotation-mode", 1)
+
+    sink = pipeline.get_by_name ("s")
+    sink.set_property ("location", "test.mp4")
+
+    # this will call set_saturation every 1s
+    GObject.timeout_add(1000, set_saturation, pipeline)
+
+    # run
+    pipeline.set_state(Gst.State.PLAYING)
+    try:
+        loop.run()
+    except Exception as e:
+        print(e)
+    # cleanup
+    pipeline.set_state(Gst.State.NULL)
+