Could you tell me async-start and async-done message in playbin?

[HoonHee Lee]

Sebastian, Thanks for your comment.

IMHO, I am a little bit agree on your comment.
I reviewed gstbin.c and I got something below functions.

In case of ASYNC-START message, they are checking the bin whether it is
top-level Bin or not.
Thus, this message is not forwarded to the application in normal case and
just uses internally.

static void
bin_handle_async_start (GstBin * bin)
{
  ...
  /* get our toplevel state */
  toplevel = BIN_IS_TOPLEVEL (bin);

  /* prepare an ASYNC_START message, we always post the start message even
if we
   * are busy with a state change or when we are NO_PREROLL. */
  if (!toplevel)
    /* non toplevel bin, prepare async-start for the parent */
    amessage = gst_message_new_async_start (GST_OBJECT_CAST (bin));
  ...
}


In case of ASYNC-DONE, if there is a pending ASYNC-START message, ASYNC-DONE
message is not posting to its bin. But, if there are no more ASYNC_START
messages, ASYNC-DONE message is posting to its bin.
Thus, I think that ASYNC_DONE message is posting only once to application.

gst_bin_handle_message_func (GstBin * bin, GstMessage * message)
{
...
  case GST_MESSAGE_ASYNC_DONE:
...
    // Because of this, All of async-done messages from child elements are
not posting to upper-layer.
    *bin_replace_message* (bin, message, GST_MESSAGE_ASYNC_START);
    /* if there are no more ASYNC_START messages, everybody posted
     * a ASYNC_DONE and we can post one on the bus. When checking, we
     * don't care who still has a pending ASYNC_START */
    if (*!find_message (bin, NULL, GST_MESSAGE_ASYNC_START)*) {
      /* nothing found, remove all old ASYNC_DONE messages */
      bin_remove_messages (bin, NULL, GST_MESSAGE_ASYNC_DONE);
      GST_DEBUG_OBJECT (bin, "async elements commited");
      /* when we get an async done message when a state change was busy, we
       * need to set the pending_done flag so that at the end of the state
       * change we can see if we need to verify pending async elements,
hence
       * the TRUE argument here. */
      *bin_handle_async_done (bin, GST_STATE_CHANGE_SUCCESS, TRUE,
          running_time);*
    } else {
      *GST_DEBUG_OBJECT (bin, "there are more async elements pending");*
    }
}



And I tested in on playbin with fakesink for audio and video.
I confirmed that ASYNC-DONE message is posting only once to application.





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