Gstreamer Python: EOS message not received?

Question

I have a Python Deepstream app (based in Gstreamer) and I want it to end properly when pressed Ctrl+C.

My pipeline has the following elements:

source -> streammux -> tee -> nvinfer -> nvvideoconvert -> nvdosd -> filesink
                        |---> filesink

My main code is:

self.loop = GObject.MainLoop.new(None, False)
GLib.unix_signal_add(-100, 2, self.handle_sigint, None)
self.bus = self.gst_pipeline.get_bus()
self.bus.add_signal_watch()
self.bus.connect("message", self.bus_message_handler)
self.gst_pipeline.set_state(Gst.State.PLAYING)
self.loop.run()

The bus message handler function:

def bus_message_handler(self, bus, message: Gst.Message) -> bool:
    t = message.type
    logger.info(f"****************** Message received {t}")
    if t == Gst.MessageType.EOS:
        logger.success("End of Stream")
        self.loop.quit()
    elif t == Gst.MessageType.WARNING:
        err, debug = message.parse_warning()
        logger.warning(f"{err}: {debug}")
    elif t == Gst.MessageType.ERROR:
        err, debug = message.parse_error()
        logger.error(f"{err}: {debug}")
        self.gst_error = f"{err}: {debug}"
        self.loop.quit()
    return True

And finally the sigint handler function:

def handle_sigint(self, user_data=None):
    logger.info("SIGINT detected. Sending EOS...")
    self.gst_pipeline.send_event(Gst.Event.new_eos())
    self.bus.timed_pop_filtered(Gst.CLOCK_TIME_NONE, Gst.MessageType.EOS)

The expected behaviour would be:

Run -> Ctrl+C pressed -> Print "SIGINT detected. Sending EOS..." -> Print "End of Stream"

But "End of Stream" is never printed out. Why the EOS message is not being received by the bus_message_handler ?

Thanks.

Answer 1

Wild guess, I haven't actually looked in the code for this detail, but I would assume that timed_pop_filtered() will take over all bus messages and either discard all messages or return the EOS in question. Since you didn't say it deadlocks/waits forever at the end I assume that timed_pop_filtered() returned the EOS correctly. Since timed_pop_filtered() will take away all messages your bus watch will not receive any more messages at this point.

So instead of grabbing away all the messages with timed_pop_filtered() you probably want to wait for a signal coming from your bus watch that is triggered whenever your EOS arrives there.