gst-basic-tutorial-1/basic-tutorial-6.c

#include <gst/gst.h>

static gboolean print_field (GQuark field,const GValue *value, gpointer pfx)
{
    gchar *str = gst_value_serialize (value);
    g_print("%s %15s: %s\n",(gchar *)pfx, g_quark_to_string(field),str);
    g_free(str);
    return TRUE;
}

static void print_caps (const GstCaps *caps, const gchar *pfx)
{
    guint i;
    g_return_if_fail (caps != NULL);

    if(gst_caps_is_any(caps))
    {
        g_print("%sANY\n",pfx);
        return;
    }
    if(gst_caps_is_empty(caps))
    {
        g_print("%sEMPTY\n",pfx);
        return;
    }

    for( i = 0; i < gst_caps_get_size(caps);i++)
    {
        GstStructure *structure = gst_caps_get_structure(caps,i);

        g_print("%s%s\n",pfx,gst_structure_get_name(structure));
        gst_structure_foreach(structure,print_field,(gpointer)pfx);
    }
}

static void print_pad_templates_information (GstElementFactory *factory)
{
    const GList *pads;
    GstStaticPadTemplate *padtemplate;

    g_print("Pad Templates for %s:\n",gst_element_factory_get_longname(factory));
    if(!gst_element_factory_get_num_pad_templates(factory))
    {
        g_print(" none\n");
        return;
    }

    pads = gst_element_factory_get_static_pad_templates(factory);
    while(pads)
    {
        padtemplate = pads->data;
        pads = g_list_next(pads);
        if(padtemplate->direction == GST_PAD_SRC)
        {
            g_print("SRC template: '%s'\n",padtemplate->name_template);
        }
        else if(padtemplate->direction == GST_PAD_SINK)
        {
            g_print("SINK template: '%s'\n",padtemplate->name_template);
        }
        else
        {
            g_print("UNKNOWN!! template: '%s'\n",padtemplate->name_template);
        }

        if(padtemplate->presence == GST_PAD_ALWAYS)
        {
            g_print(" Availability: Always\n");
        }
        else if(padtemplate->presence == GST_PAD_SOMETIMES)
        {
            g_print(" Availability: Sometimes\n");
        }
        else if(padtemplate->presence == GST_PAD_REQUEST)
        {
            g_print(" Availability: On request\n");
        }
        else
        {
            g_print(" Availability: UNKNOWN!!!\n");
        }

        if(padtemplate->static_caps.string)
        {
            GstCaps *caps;
            g_print(" Capabilities: \n");
            caps = gst_static_caps_get(&padtemplate->static_caps);
            print_caps(caps, " ");
            gst_caps_unref(caps);
        }
        g_print("\n");
    }
}

static void print_pad_capabilities(GstElement *element, gchar *pad_name)
{
    GstPad *pad = NULL;
    GstCaps *caps = NULL;

    pad = gst_element_get_static_pad(element, pad_name);
    if(!pad)
    {
        g_printerr("Could not retrieve pad '%s'\n",pad_name);
        return;
    }

    caps = gst_pad_get_current_caps(pad);
    if(!caps)
    {
        caps = gst_pad_query_caps(pad,NULL);

        g_print("Caps for the %s pad:\n",pad_name);
        print_caps(caps," ");
        gst_caps_unref(caps);
        gst_object_unref(pad);
    }
}

int main(int argc, char *argv[])
{
    GstElement *pipeline, *source, *sink;
    GstElementFactory *source_factory,*sink_factory;
    GstBus *bus;
    GstMessage *msg;
    GstStateChangeReturn ret;
    gboolean terminate = FALSE;

    gst_init(&argc,&argv);

    source_factory = gst_element_factory_find("audiotestsrc");
    sink_factory = gst_element_factory_find("autoaudiosink");
    if(!source_factory || !sink_factory)
    {
        g_printerr("Not all element fatories could be created.\n");
        return -1;
    }

    print_pad_templates_information(source_factory);
    print_pad_templates_information(sink_factory);

    source = gst_element_factory_create(source_factory,"source");
    sink = gst_element_factory_create(sink_factory,"sink");

    pipeline = gst_pipeline_new("test-pipeline");

    if(!pipeline || !source || !sink)
    {
        g_printerr("Not all element could be created!\n");
        return -1;
    }

    gst_bin_add_many(GST_BIN(pipeline),source,sink,NULL);
    if(gst_element_link(source,sink)!=TRUE)
    {
        g_printerr("Elements could not be linked!\n");
        g_object_unref(pipeline);
        return -1;
    }

    g_print("In NULL state:\n");
    print_pad_capabilities(sink,"sink");

    ret = gst_element_set_state(pipeline,GST_STATE_PLAYING);
    if(ret == GST_STATE_CHANGE_FAILURE)
    {
        g_printerr("Unable to set the pipeline to the playing state (check the bus for error message).\n");
    }

    bus = gst_element_get_bus(pipeline);
    do
    {
        msg = gst_bus_timed_pop_filtered(bus, GST_CLOCK_TIME_NONE, GST_MESSAGE_ERROR | GST_MESSAGE_EOS |GST_MESSAGE_STATE_CHANGED);

        if(msg != NULL)
        {
            GError *err;
            gchar *debug_info;

            switch (GST_MESSAGE_TYPE (msg))
            {
                case GST_MESSAGE_ERROR:
                    gst_message_parse_error(msg, &err, &debug_info);
                    g_printerr("Error received from element %s: %s\n",GST_OBJECT_NAME(msg->src),err->message);
                    g_printerr("Debugging information: %s\n",debug_info ? debug_info : "none");
                    g_clear_error(&err);
                    g_free(debug_info);
                    terminate = TRUE;
                break;
                case GST_MESSAGE_EOS:
                    g_print("End-Of-Stream reached.\n");
                    terminate = TRUE;
                break;
                case GST_MESSAGE_STATE_CHANGED:
                    if(GST_MESSAGE_SRC(msg) == GST_OBJECT(pipeline))
                    {
                        GstState old_state,new_state,pending_state;
                        gst_message_parse_state_changed(msg,&old_state,&new_state,&pending_state);
                        g_print("\nPipeline state changed from %s to %s:\n",
                            gst_element_state_get_name(old_state),gst_element_state_get_name(new_state));
                        print_pad_capabilities(sink,"sink");
                    }
                break;
                default:
                    g_printerr("Unexpected message received.\n");
                break;
            }
            gst_message_unref(msg);
        }
    }while(!terminate);

    gst_object_unref(bus);
    gst_element_set_state(pipeline,GST_STATE_NULL);
    gst_object_unref(pipeline);
    gst_object_unref(source_factory);
    gst_object_unref(sink_factory);
    return;
}