I am using gstreamer v1.14.5 with Python bindings. I have created a plugin by subclassing the GstBase.BaseTransform class and overriding its do_transform_ip method. The plugin draws a rectangle on the video frame.
class MyPlugin(GstBase.BaseTransform):
def do_transform_ip(self, buffer: Gst.Buffer) -> Gst.FlowReturn:
logging.info("in do_transform_ip")
# draw rectangle on the video frame
# I won't go into the implementation details here
return Gst.FlowReturn.OK
The plugin works well when used with gst-launch-1.0:
gst-launch-1.0 videotestsrc ! myplugin ! videoconvert ! autovideosink
I have added debug messages to the do_transform_ip and those messages are displayed in the terminal. And rectangle is drawn on the video.
However when I create the pipeline manually, like in the code below, it seems like the plugin's do_transform_ip method is not called.
pipeline = Gst.Pipeline.new("test-pipeline")
source = Gst.ElementFactory.make("videotestsrc")
my_plugin = Gst.ElementFactory.make("myplugin")
converter = Gst.ElementFactory.make("videoconvert")
sink = Gst.ElementFactory.make("autovideosink")
pipeline.add(source)
pipeline.add(my_plugin)
pipeline.add(converter)
pipeline.add(sink)
source.link(my_plugin)
my_plugin.link(converter)
converter.link(sink)
pipeline.set_state(Gst.State.PLAYING)
No log messages are displayed in the terminal and the rectangle is not drawn on the video. The video output of videotestsrc is displayed properly, but without the rectangle.
What am I missing here?
