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Add a simple example of inclusion
0.7.9.3 is needed, but it's pushed on pip so it shouldn't be too complicated. Need the C extension as well, README updated to reflect that. This allowed noticing and fixing two errors in the link_to_multiplexer snippet, as clang complained, check the differences between the previous version and the new one :)
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Mathieu Duponchelle
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e256a61106
6 changed files with 128 additions and 128 deletions
3
README
3
README
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@ -24,6 +24,9 @@ for *stable* automatic formatting.
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* Follow [hotdoc's installation guide](https://people.collabora.com/~meh/hotdoc_hotdoc/html/installing.html),
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preferably in a virtualenv.
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* We *experimentally* use the hotdoc C extension to include functions by
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name, follow the steps outlined [here](https://github.com/hotdoc/hotdoc_c_extension)
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* Optionally install the `hotdoc_search_extension`:
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```
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82
examples/bus_example.c
Normal file
82
examples/bus_example.c
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@ -0,0 +1,82 @@
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#include <gst/gst.h>
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static GMainLoop *loop;
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static gboolean
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my_bus_callback (GstBus *bus,
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GstMessage *message,
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gpointer data)
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{
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g_print ("Got %s message\n", GST_MESSAGE_TYPE_NAME (message));
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switch (GST_MESSAGE_TYPE (message)) {
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case GST_MESSAGE_ERROR: {
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GError *err;
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gchar *debug;
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gst_message_parse_error (message, &err, &debug);
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g_print ("Error: %s\n", err->message);
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g_error_free (err);
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g_free (debug);
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g_main_loop_quit (loop);
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break;
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}
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case GST_MESSAGE_EOS:
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/* end-of-stream */
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g_main_loop_quit (loop);
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break;
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default:
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/* unhandled message */
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break;
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}
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/* we want to be notified again the next time there is a message
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* on the bus, so returning TRUE (FALSE means we want to stop watching
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* for messages on the bus and our callback should not be called again)
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*/
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return TRUE;
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}
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gint
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main (gint argc,
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gchar *argv[])
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{
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GstElement *pipeline;
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GstBus *bus;
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guint bus_watch_id;
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/* init */
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gst_init (&argc, &argv);
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/* create pipeline, add handler */
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pipeline = gst_pipeline_new ("my_pipeline");
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/* adds a watch for new message on our pipeline's message bus to
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* the default GLib main context, which is the main context that our
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* GLib main loop is attached to below
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*/
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bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
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bus_watch_id = gst_bus_add_watch (bus, my_bus_callback, NULL);
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gst_object_unref (bus);
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/* [...] */
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/* create a mainloop that runs/iterates the default GLib main context
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* (context NULL), in other words: makes the context check if anything
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* it watches for has happened. When a message has been posted on the
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* bus, the default main context will automatically call our
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* my_bus_callback() function to notify us of that message.
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* The main loop will be run until someone calls g_main_loop_quit()
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*/
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loop = g_main_loop_new (NULL, FALSE);
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g_main_loop_run (loop);
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/* clean up */
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gst_element_set_state (pipeline, GST_STATE_NULL);
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gst_object_unref (pipeline);
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g_source_remove (bus_watch_id);
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g_main_loop_unref (loop);
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return 0;
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}
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38
examples/snippets.c
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38
examples/snippets.c
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@ -0,0 +1,38 @@
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#include <gst/gst.h>
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static void
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link_to_multiplexer (GstPad *tolink_pad,
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GstElement *mux)
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{
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GstPad *pad;
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gchar *srcname, *sinkname;
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srcname = gst_pad_get_name (tolink_pad);
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pad = gst_element_get_compatible_pad (mux, tolink_pad, NULL);
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gst_pad_link (tolink_pad, pad);
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sinkname = gst_pad_get_name (pad);
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gst_object_unref (GST_OBJECT (pad));
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g_print ("A new pad %s was created and linked to %s\n", sinkname, srcname);
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g_free (sinkname);
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g_free (srcname);
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}
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static void
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some_function (GstElement *tee)
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{
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GstPad * pad;
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gchar *name;
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pad = gst_element_get_request_pad (tee, "src%d");
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name = gst_pad_get_name (pad);
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g_print ("A new pad %s was created\n", name);
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g_free (name);
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/* here, you would link the pad */
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/* [..] */
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/* and, after doing that, free our reference */
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gst_object_unref (GST_OBJECT (pad));
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}
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@ -5,5 +5,6 @@
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"output": "built_doc",
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"project_name": "gstdotcom",
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"sitemap": "sitemap.txt",
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"extra_assets": ["attachments", "images"]
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"extra_assets": ["attachments", "images"],
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"pkg_config_packages": ["gstreamer-1.0"]
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}
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@ -39,94 +39,8 @@ There are two different ways to use a bus:
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- Check for messages on the bus yourself. This can be done using
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`gst_bus_peek ()` and/or `gst_bus_poll ()`.
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<!-- end list -->
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```
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#include <gst/gst.h>
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static GMainLoop *loop;
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static gboolean
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my_bus_callback (GstBus *bus,
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GstMessage *message,
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gpointer data)
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{
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g_print ("Got %s message\n", GST_MESSAGE_TYPE_NAME (message));
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switch (GST_MESSAGE_TYPE (message)) {
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case GST_MESSAGE_ERROR: {
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GError *err;
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gchar *debug;
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gst_message_parse_error (message, &err, &debug);
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g_print ("Error: %s\n", err->message);
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g_error_free (err);
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g_free (debug);
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g_main_loop_quit (loop);
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break;
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}
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case GST_MESSAGE_EOS:
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/* end-of-stream */
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g_main_loop_quit (loop);
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break;
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default:
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/* unhandled message */
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break;
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}
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/* we want to be notified again the next time there is a message
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* on the bus, so returning TRUE (FALSE means we want to stop watching
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* for messages on the bus and our callback should not be called again)
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*/
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return TRUE;
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}
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gint
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main (gint argc,
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gchar *argv[])
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{
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GstElement *pipeline;
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GstBus *bus;
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guint bus_watch_id;
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/* init */
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gst_init (&argc, &argv);
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/* create pipeline, add handler */
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pipeline = gst_pipeline_new ("my_pipeline");
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/* adds a watch for new message on our pipeline's message bus to
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* the default GLib main context, which is the main context that our
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* GLib main loop is attached to below
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*/
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bus = gst_pipeline_get_bus (GST_PIPELINE (pipeline));
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bus_watch_id = gst_bus_add_watch (bus, my_bus_callback, NULL);
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gst_object_unref (bus);
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[..]
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/* create a mainloop that runs/iterates the default GLib main context
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* (context NULL), in other words: makes the context check if anything
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* it watches for has happened. When a message has been posted on the
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* bus, the default main context will automatically call our
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* my_bus_callback() function to notify us of that message.
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* The main loop will be run until someone calls g_main_loop_quit()
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*/
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loop = g_main_loop_new (NULL, FALSE);
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g_main_loop_run (loop);
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/* clean up */
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gst_element_set_state (pipeline, GST_STATE_NULL);
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gst_object_unref (pipeline);
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g_source_remove (bus_watch_id);
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g_main_loop_unref (loop);
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return 0;
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}
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```
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{{ examples/bus_example.c }}
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It is important to know that the handler will be called in the thread
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context of the mainloop. This means that the interaction between the
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@ -123,26 +123,7 @@ the stream, it can simply request a new output pad from the tee element.
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The following piece of code shows how you can request a new output pad
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from a “tee” element:
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```
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static void
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some_function (GstElement *tee)
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{
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GstPad * pad;
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gchar *name;
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pad = gst_element_get_request_pad (tee, "src%d");
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name = gst_pad_get_name (pad);
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g_print ("A new pad %s was created\n", name);
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g_free (name);
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/* here, you would link the pad */
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[..]
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/* and, after doing that, free our reference */
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gst_object_unref (GST_OBJECT (pad));
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}
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```
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{{ examples/snippets.c#some_function }}
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The `gst_element_get_request_pad ()` method can be used to get a pad
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from the element based on the name of the pad template. It is also
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@ -153,26 +134,7 @@ element and you need to request a pad that is compatible. The method
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pad, as shown in the next example. It will request a compatible pad from
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an Ogg multiplexer from any input.
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```
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static void
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link_to_multiplexer (GstPad *tolink_pad,
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GstElement *mux)
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{
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GstPad *pad;
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gchar *srcname, *sinkname;
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srcname = gst_pad_get_name (tolink_pad);
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pad = gst_element_get_compatible_pad (mux, tolink_pad);
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gst_pad_link (tolinkpad, pad);
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sinkname = gst_pad_get_name (pad);
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gst_object_unref (GST_OBJECT (pad));
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g_print ("A new pad %s was created and linked to %s\n", sinkname, srcname);
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g_free (sinkname);
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g_free (srcname);
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}
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```
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{{ examples/snippets.c#link_to_multiplexer }}
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# Capabilities of a pad
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