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#include <gst/gst.h>
/* Functions below print the Capabilities in a human-friendly format */
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);
}
}
/* Prints information about a Pad Template, including its Capabilities */
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");
}
}
/* Shows the CURRENT capabilities of the requested pad in the given element */
static void print_pad_capabilities (GstElement *element, gchar *pad_name) {
GstPad *pad = NULL;
GstCaps *caps = NULL;
/* Retrieve pad */
pad = gst_element_get_static_pad (element, pad_name);
if (!pad) {
g_printerr ("Could not retrieve pad '%s'\n", pad_name);
return;
}
/* Retrieve negotiated caps (or acceptable caps if negotiation is not finished yet) */
caps = gst_pad_get_current_caps (pad);
if (!caps)
caps = gst_pad_query_caps (pad, NULL);
/* Print and free */
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;
/* Initialize GStreamer */
gst_init (&argc, &argv);
/* Create the element factories */
source_factory = gst_element_factory_find ("audiotestsrc");
sink_factory = gst_element_factory_find ("autoaudiosink");
if (!source_factory || !sink_factory) {
g_printerr ("Not all element factories could be created.\n");
return -1;
}
/* Print information about the pad templates of these factories */
print_pad_templates_information (source_factory);
print_pad_templates_information (sink_factory);
/* Ask the factories to instantiate actual elements */
source = gst_element_factory_create (source_factory, "source");
sink = gst_element_factory_create (sink_factory, "sink");
/* Create the empty pipeline */
pipeline = gst_pipeline_new ("test-pipeline");
if (!pipeline || !source || !sink) {
g_printerr ("Not all elements could be created.\n");
return -1;
}
/* Build the pipeline */
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");
gst_object_unref (pipeline);
return -1;
}
/* Print initial negotiated caps (in NULL state) */
g_print ("In NULL state:\n");
print_pad_capabilities (sink, "sink");
/* Start playing */
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 messages).\n");
}
/* Wait until error, EOS or State Change */
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);
/* Parse message */
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:
/* We are only interested in state-changed messages from the pipeline */
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 the current capabilities of the sink element */
print_pad_capabilities (sink, "sink");
}
break;
default:
/* We should not reach here because we only asked for ERRORs, EOS and STATE_CHANGED */
g_printerr ("Unexpected message received.\n");
break;
}
gst_message_unref (msg);
}
} while (!terminate);
/* Free resources */
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 0;
}
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