&GStreamer; includes several higher-level components to simplify your applications life. All of the components discussed here (for now) are targetted at media playback. The idea of each of these components is to integrate as closely as possible with a &GStreamer; pipeline, but to hide the complexity of media type detection and several other rather complex topics that have been discussed in . We currently recommend people to use either playbin (see ) or decodebin (see ), depending on their needs. The other components discussed here are either outdated or deprecated. The documentation is provided for legacy purposes. Use of those other components is not recommended. Playbin is an element that can be created using the standard &GStreamer; API (e.g. gst_element_factory_make ()). The factory is conveniently called playbin. By being a GstElement, playbin automatically supports all of the features of this class, including error handling, tag support, state handling, getting stream positions, seeking, and so on. Setting up a playbin pipeline is as simple as creating an instance of the playbin element, setting a file location (this has to be a valid URI, so <protocol>://<location>, e.g. file:///tmp/my.ogg or http://www.example.org/stream.ogg) using the uri property on playbin, and then setting the element to the GST_STATE_PLAYING state. Internally, playbin uses threads, so there's no need to iterate the element or anything. However, one thing to keep in mind is that signals fired by playbin might come from another than the main thread, so be sure to keep this in mind in your signal handles. Most application programmers will want to use a function such as g_idle_add () to make sure that the signal is handled in the main thread. #include <gst/gst.h> static void cb_eos (GstElement *play, gpointer data) { gst_main_quit (); } static void cb_error (GstElement *play, GstElement *src, GError *err, gchar *debug, gpointer data) { g_print ("Error: %s\n", err->message); } gint main (gint argc, gchar *argv[]) { GstElement *play; /* init GStreamer */ gst_init (&argc, &argv); /* make sure we have a URI */ if (argc != 2) { g_print ("Usage: %s <URI>\n", argv[0]); return -1; } /* set up */ play = gst_element_factory_make ("playbin", "play"); g_object_set (G_OBJECT (play), "uri", argv[1], NULL); g_signal_connect (play, "eos", G_CALLBACK (cb_eos), NULL); g_signal_connect (play, "error", G_CALLBACK (cb_error), NULL); if (gst_element_set_state (play, GST_STATE_PLAYING) != GST_STATE_SUCCESS) { g_print ("Failed to play\n"); return -1; } /* now run */ gst_main (); /* also clean up */ gst_element_set_state (play, GST_STATE_NULL); gst_object_unref (GST_OBJECT (play)); return 0; } Playbin has several features that have been discussed previously: Settable video and audio output (using the video-sink and audio-sink properties). Mostly controllable and trackable as a GstElement, including error handling, eos handling, tag handling, state handling, media position handling and seeking. Buffers network-sources. Supports visualizations for audio-only media. Supports subtitles, both in the media as well as from separate files. Supports stream selection and disabling. If your media has multiple audio or subtitle tracks, you can dynamically choose which one to play back, or decide to turn it off alltogther (which is especially useful to turn off subtitles). Decodebin is the actual autoplugger backend of playbin, which was discussed in the previous section. Decodebin will, in short, accept input from a source that is linked to its sinkpad and will try to detect the media type contained in the stream, and set up decoder routines for each of those. It will automatically select decoders. For each decoded stream, it will emit the new-decoded-pad signal, to let the client know about the newly found decoded stream. For unknown streams (which might be the whole stream), it will emit the unknown-type signal. The application is then responsible for reporting the error to the user. The example code below will play back an audio stream of an input file. For readability, it does not include any error handling of any sort. #include <gst/gst.h> GstElement *pipeline, *audio; GstPad *audiopad; static void cb_newpad (GstElement *decodebin, GstPad *pad, gboolean last, gpointer data) { GstCaps *caps; GstStructure *str; /* only link audio; only link once */ if (GST_PAD_IS_LINKED (audiopad)) return; caps = gst_pad_get_caps (pad); str = gst_caps_get_structure (caps, 0); if (!g_strrstr (gst_structure_get_name (str), "audio")) return; /* link'n'play */ gst_pad_link (pad, audiopad); gst_bin_add (GST_BIN (pipeline), audio); gst_bin_sync_children_state (GST_BIN (pipeline)); } gint main (gint argc, gchar *argv[]) { GstElement *src, *dec, *conv, *scale, *sink; /* init GStreamer */ gst_init (&argc, &argv); /* make sure we have input */ if (argc != 2) { g_print ("Usage: %s <filename>\n", argv[0]); return -1; } /* setup */ pipeline = gst_pipeline_new ("pipeline"); src = gst_element_factory_make ("filesrc", "source"); g_object_set (G_OBJECT (src), "location", argv[1], NULL); dec = gst_element_factory_make ("decodebin", "decoder"); g_signal_connect (dec, "new-decoded-pad", G_CALLBACK (cb_newpad), NULL); audio = gst_bin_new ("audiobin"); conv = gst_element_factory_make ("audioconvert", "aconv"); audiopad = gst_element_get_pad (conv, "sink"); scale = gst_element_factory_make ("audioscale", "scale"); sink = gst_element_factory_make ("alsasink", "sink"); gst_bin_add_many (GST_BIN (audio), conv, scale, sink, NULL); gst_element_link_many (conv, scale, sink, NULL); gst_bin_add_many (GST_BIN (pipeline), src, dec, NULL); gst_element_link (src, dec); /* run */ gst_element_set_state (audio, GST_STATE_PAUSED); gst_element_set_state (pipeline, GST_STATE_PLAYING); while (gst_bin_iterate (GST_BIN (pipeline))) ; /* cleanup */ gst_element_set_state (pipeline, GST_STATE_NULL); gst_object_unref (GST_OBJECT (pipeline)); return 0; } Decodebin, similar to playbin, supports the following features: Can decode an unlimited number of contained streams to decoded output pads. Is handled as a GstElement in all ways, including tag or error forwarding and state handling. Although decodebin is a good autoplugger, there's a whole lot of things that it does not do and is not intended to do: Taking care of input streams with a known media type (e.g. a DVD, an audio-CD or such). Selection of streams (e.g. which audio track to play in case of multi-language media streams). Overlaying subtitles over a decoded video stream. Decodebin can be easily tested on the commandline, e.g. by using the command gst-launch-0.8 filesrc location=file.ogg ! decodebin ! audioconvert ! audioscale ! alsasink. Spider is an autoplugger that looks and feels very much like decodebin. On the commandline, you can literally switch between spider and decodebin and it'll mostly just work. Try, for example, gst-launch-0.8 filesrc location=file.ogg ! spider ! audioconvert ! audioscale ! alsasink. Although the two may seem very much alike from the outside, they are very different from the inside. Those internal differences are the main reason why spider is currently considered deprecated (along with the fact that it was hard to maintain). As opposed to decodebin, spider does not decode pads and emit signals for each detected stream. Instead, you have to add output sinks to spider by create source request pads and connecting those to sink elements. This means that streams decoded by spider cannot be dynamic. Also, spider uses many loop-based elements internally, which is rather heavy scheduler-wise. Code for using spider would look almost identical to the code of decodebin, and is therefore omitted. Also, featureset and limitations are very much alike, except for the above-mentioned extra limitations for spider with respect to decodebin. GstPlay is a GtkWidget with a simple API to play, pause and stop a media file. GstEditor is a set of widgets to display a graphical representation of a pipeline.