Re: Gstreamermm plugin initialization error

[Fernando Herrero Carrón <elferdo gmail com>]

El sáb, 25-06-2011 a las 18:30 +0200, Krzesimir Nowak escribió:
> On Sat, 2011-06-25 at 17:43 +0200, Fernando Herrero Carrón wrote:
> > Hello everyone,
> > 
> > I am beginning to play with gstreamermm (and gstreamer in general, for
> > that matter) eventhough I have been using gtk-- for a long time.
> > 
> > I'm using gstreamermm on FreeBSD 8.2-STABLE with the system compiler:
> > 
> > g++ (GCC) 4.2.2 20070831 prerelease [FreeBSD]
> > 
> > Compiling and installing gstreamermm from ports was flawless, and I can
> > compile, link and run simple examples against it. However, some plugins
> > that work OK for C programs fail to load when using the C++ wrappers.
> > 
> > For example, running
> > 
> > $> gstreamer-properties --gst-debug-level=5
> > 
> > yields
> > 
> > [...]
> > GST_PLUGIN_LOADING gstpluginfeature.c:107:gst_plugin_feature_load: loading plugin for feature 0x8067007e0; 'fakesink'
> > GST_PLUGIN_LOADING gstpluginfeature.c:111:gst_plugin_feature_load: loading plugin coreelements
> > GST_PLUGIN_LOADING gstplugin.c:1293:gst_plugin_load_by_name: looking up plugin coreelements in default registry
> > GST_PLUGIN_LOADING gstplugin.c:1296:gst_plugin_load_by_name: loading plugin coreelements from file /usr/local/lib/gstreamer-0.10/libgstcoreelements.so
> > GST_PLUGIN_LOADING gstplugin.c:737:gst_plugin_load_file: attempt to load plugin "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so"
> > GST_PLUGIN_LOADING gstplugin.c:834:gst_plugin_load_file: Plugin 0x806767150 for file "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so" prepared, calling entry function...
> > GST_PLUGIN_LOADING gstplugin.c:841:gst_plugin_load_file: Plugin 0x806767150 for file "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so" prepared, registering...
> > GST_PLUGIN_LOADING gstplugin.c:540:gst_plugin_register_func: plugin "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so" looks good
> > GST_ELEMENT_FACTORY gstelementfactory.c:232:gst_element_register:<registry0> update existing feature 0x8067005a0 (capsfilter)
> > GST_ELEMENT_FACTORY gstelementfactory.c:232:gst_element_register:<registry0> update existing feature 0x8067006c0 (fakesrc)
> > GST_ELEMENT_FACTORY gstelementfactory.c:232:gst_element_register:<registry0> update existing feature 0x8067007e0 (fakesink)
> > [...]
> > 
> > This looks like once a plugin gets loaded, all its features get registered.
> > 
> > Now I compile the following program:
> > 
> > #include <gstreamermm.h>
> > 
> > int main(int argc, char **argv) {
> > 	// Initialize Gstreamermm:
> > 	Gst::init(argc, argv);
> > 
> > 	// Create elements:
> > 	Glib::RefPtr<Gst::Element> fakesrc = Gst::ElementFactory::create_element("fakesrc");
> > 
> > 	if(fakesrc == Glib::RefPtr<Gst::Element>(NULL))
> > 		throw -1;
> > 
> > 	return 0;
> > }
> > 
> > And if I run it with --gst-debug-level=5 I get the following errors:
> > 
> > [...]
> > GST_PLUGIN_LOADING gstpluginfeature.c:111:gst_plugin_feature_load: loading plugin coreelements
> > GST_PLUGIN_LOADING gstplugin.c:1293:gst_plugin_load_by_name: looking up plugin coreelements in default registry
> > GST_PLUGIN_LOADING gstplugin.c:1296:gst_plugin_load_by_name: loading plugin coreelements from file /usr/local/lib/gstreamer-0.10/libgstcoreelements.so
> > GST_PLUGIN_LOADING gstpluginfeature.c:116:gst_plugin_feature_load: loaded plugin coreelements
> > GST_PLUGIN_LOADING gstpluginfeature.c:146:gst_plugin_feature_load: Tried to load plugin containing feature 'fakesrc', but feature was not found.
> > 
> > (mygstreamer:31703): GStreamer-CRITICAL **: gst_element_factory_get_element_type: assertion `GST_IS_ELEMENT_FACTORY (factory)' failed
> > 
> > (mygstreamer:31703): GLib-GObject-CRITICAL **: g_object_unref: assertion `G_IS_OBJECT (object)' failed
> > 
> > (mygstreamer:31703): GStreamer-CRITICAL **: gst_element_register: assertion `g_type_is_a (type, GST_TYPE_ELEMENT)' failed
> > GST_PLUGIN_LOADING gstplugin.c:559:gst_plugin_register_func: plugin "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so" failed to initialise
> > GST_PLUGIN_LOADING gstplugin.c:846:gst_plugin_load_file: gst_plugin_register_func failed for plugin "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so"
> > GST_PLUGIN_LOADING gstplugin.c:1301:gst_plugin_load_by_name: load_plugin error: File "/usr/local/lib/gstreamer-0.10/libgstcoreelements.so" appears to be a GStreamer plugin, but it failed to initialize
> > GST_PLUGIN_LOADING gstpluginfeature.c:133:gst_plugin_feature_load: Failed to load plugin containing feature 'capsfilter'.
> > [...]
> > GST_PLUGIN_LOADING gstpluginfeature.c:146:gst_plugin_feature_load: Tried to load plugin containing feature 'fakesrc', but feature was not found.
> > GST_ELEMENT_FACTORY gstelementfactory.c:409:gst_element_factory_create:<elementfactory3> loading plugin containing feature (null) returned NULL!
> > GST_ELEMENT_FACTORY gstelementfactory.c:470:gst_element_factory_make:<elementfactory3> couldn't create instance!
> > terminate called after throwing an instance of 'int'
> > 
> > 
> > Here it looks like it is trying to initialize a plugin that has been
> > already loaded, is that possible?

> Shooting in the dark here, but maybe everything is alright. Probably
> this strange Glib::RefPtr<Gst::Element>(NULL) is messing with you. Try
> using 'if (fakesrc) { ... }'.
> 
> I'm no gstreamer guy, but this use of Glib::RefPtr caught my eye.

Thanks for the idea. I checked with gdb and the pointer in the RefPtr is
actually NULL, so there is something more going on here. If I create a
different element, "capsfilter" for instance, this one works OK. This
feature appears as succesfully registered in the log.

By the way, I forgot to mention that I am using gstreamer-0.10.35 and
gstreamermm-0.10.9. Hmmm, do those versions match? I'm going to check,
just in case.

Thanks,
Fernando