[Bug 698851] playbin: ability to mix or play multiple audio and text streams simultaneously

[GStreamer (bugzilla.gnome.org)]

https://bugzilla.gnome.org/show_bug.cgi?id=698851
  GStreamer | gst-plugins-base | git

--- Comment #40 from Brendan Long <self at brendanlong.com> 2013-05-29 16:46:33 UTC ---
Created an attachment (id=245564)
 View: https://bugzilla.gnome.org/attachment.cgi?id=245564
 Review: https://bugzilla.gnome.org/review?bug=698851&attachment=245564

Don't add an extra ref to custom combiners in pad_added_cb

Short version: `gst_bin_add` refs custom_combiner for us, so we don't need to
ref it ourselves.

The problem is here in `pad_added_cb`:

    // custom_combiner has one ref
    if (custom_combiner)
      combine->combiner = gst_object_ref (custom_combiner);
    else
      combine->combiner = gst_element_factory_make ("input-selector", NULL);
    // now custom_combiner has two refs
    // default combiner has one ref
    // ...
    gst_bin_add (GST_BIN_CAST (playbin), combine->combiner);
    // custom_combiner has three refs
    // default combiner has one ref

Then in `pad_removed_cb`:

      // custom combiner starts with three refs
      // default combiner starts with one ref

      gst_element_set_state (combine->combiner, GST_STATE_NULL);
      gst_bin_remove (GST_BIN_CAST (playbin), combine->combiner);
      // custom combiner has 2 refs
      // default combiner has 0 refs
      combine->combiner = NULL;

The problem is that we add two ref's for custom combiners and only one for
normal combiners.

I'm actually confused about where the elements are being ref'd in `gst_bin_add`
(I looked at the source and don't see it), but I can confirm that it's
happening with logging:

      g_print("refs before add %d\n",
GST_OBJECT_REFCOUNT_VALUE(combine->combiner)); // 2
      gst_bin_add (GST_BIN_CAST (playbin), combine->combiner);
      g_print("refs after add %d\n",
GST_OBJECT_REFCOUNT_VALUE(combine->combiner)); // 3

Is the `transfer full` annotation on `gst_bin_add` correct? I thought transfer
full meant that the function doesn't add another reference.

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