Flow of PAUSE request from gstreamer to upper QT application.

[sathish]

Hi,

I have a request to CORK/PAUSE from Pulseaudio. This initiates the function
"gst_pulsering_stream_event_cb" in program pulsesink.c. I have pasted the
function below..

static void
gst_pulsering_stream_event_cb (pa_stream * p, const char *name,
    pa_proplist * pl, void *userdata)
{
  GstPulseSink *psink;
  GstPulseRingBuffer *pbuf;

  pbuf = GST_PULSERING_BUFFER_CAST (userdata);
  psink = GST_PULSESINK_CAST (GST_OBJECT_PARENT (pbuf));

 * if (!strcmp (name, PA_STREAM_EVENT_REQUEST_CORK)) {
    /* the stream wants to PAUSE, post a message for the application. */
    GST_DEBUG_OBJECT (psink, "got request for CORK");
    gst_element_post_message (GST_ELEMENT_CAST (psink),
        gst_message_new_request_state (GST_OBJECT_CAST (psink),
            GST_STATE_PAUSED));
*
  } else if (!strcmp (name, PA_STREAM_EVENT_REQUEST_UNCORK)) {
    GST_DEBUG_OBJECT (psink, "got request for UNCORK");
    gst_element_post_message (GST_ELEMENT_CAST (psink),
        gst_message_new_request_state (GST_OBJECT_CAST (psink),
            GST_STATE_PLAYING));
  } else if (!strcmp (name, PA_STREAM_EVENT_FORMAT_LOST)) {
    GstEvent *renego;

    if (g_atomic_int_get (&psink->format_lost)) {
      /* Duplicate event before we're done reconfiguring, discard */
      return;
    }

    GST_DEBUG_OBJECT (psink, "got FORMAT LOST");
    g_atomic_int_set (&psink->format_lost, 1);
    psink->format_lost_time = g_ascii_strtoull (pa_proplist_gets (pl,
            "stream-time"), NULL, 0) * 1000;

    g_free (psink->device);
    psink->device = g_strdup (pa_proplist_gets (pl, "device"));

    /* FIXME: send reconfigure event instead and let decodebin/playbin
     * handle that. Also take care of ac3 alignment */
    renego = gst_event_new_custom (GST_EVENT_CUSTOM_UPSTREAM,
        gst_structure_new_empty ("pulse-format-lost"));

#if 0
    if (g_str_equal (gst_structure_get_name (st), "audio/x-eac3")) {
      GstStructure *event_st = gst_structure_new ("ac3parse-set-alignment",
          "alignment", G_TYPE_STRING, pbin->dbin ? "frame" : "iec61937",
NULL);

      if (!gst_pad_push_event (pbin->sinkpad,
              gst_event_new_custom (GST_EVENT_CUSTOM_UPSTREAM, event_st)))
        GST_WARNING_OBJECT (pbin->sinkpad, "Could not update alignment");
    }
#endif

    if (!gst_pad_push_event (GST_BASE_SINK (psink)->sinkpad, renego)) {
      /* Nobody handled the format change - emit an error */
      GST_ELEMENT_ERROR (psink, STREAM, FORMAT, ("Sink format changed"),
          ("Sink format changed"));
    }
  } else {
    GST_DEBUG_OBJECT (psink, "got unknown event %s", name);
  }
}


This request (highlited part) needs to communicated to my upper level QT
application.

QT communicates with GSTREAMER through "PHONON - GSTREAMER BACKEND"..

 I am exactly not sure how the message posted in the function
"gst_pulsering_stream_event_cb" in program pulsesink.c reaches the
phonon-gstreamer backend and proceeds then on.

In short, how to find which function catches the bus message. 

I had tried to look at PHONON source code.. I could deduce to this position
only..

I feel that function "MediaObject::handleBusMessage(const Message &message)"
is called. Can anybody tell whether this correct or a way to validate how
this can be verified ??

Thanks,
Sathish





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