/* GStreamer * Copyright (C) <1999> Erik Walthinsen * * This library is free software; you can redistribute it and/or * modify it under the terms of the GNU Library General Public * License as published by the Free Software Foundation; either * version 2 of the License, or (at your option) any later version. * * This library is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU * Library General Public License for more details. * * You should have received a copy of the GNU Library General Public * License along with this library; if not, write to the * Free Software Foundation, Inc., 59 Temple Place - Suite 330, * Boston, MA 02111-1307, USA. */ /* First, include the header file for the plugin, to bring in the * object definition and other useful things. */ #include #include "example.h" /* The ElementDetails structure gives a human-readable description * of the plugin, as well as author and version data. */ static GstElementDetails example_details = { "An example plugin", "Example/FirstExample", "LGPL", "Shows the basic structure of a plugin", "0.1", "your name ", "(C) 2001", }; /* These are the signals that this element can fire. They are zero- * based because the numbers themselves are private to the object. * LAST_SIGNAL is used for initialization of the signal array. */ enum { ASDF, /* FILL ME */ LAST_SIGNAL }; /* Arguments are identified the same way, but cannot be zero, so you * must leave the ARG_0 entry in as a placeholder. */ enum { ARG_0, ARG_ACTIVE, /* FILL ME */ }; /* The PadFactory structures describe what pads the element has or * can have. They can be quite complex, but for this example plugin * they are rather simple. */ GST_PAD_TEMPLATE_FACTORY (sink_factory, "sink", /* The name of the pad */ GST_PAD_SINK, /* Direction of the pad */ GST_PAD_ALWAYS, /* The pad exists for every instance */ GST_CAPS_NEW ( "example_sink", /* The name of the caps */ "unknown/unknown", /* The overall MIME/type */ "foo", GST_PROPS_INT (1), /* An integer property */ "bar", GST_PROPS_BOOLEAN (TRUE), /* A boolean */ "baz", GST_PROPS_LIST ( /* A list of values for */ GST_PROPS_INT (1), GST_PROPS_INT (3) ) ) ); /* This factory is much simpler, and defines the source pad. */ GST_PAD_TEMPLATE_FACTORY (src_factory, "src", GST_PAD_SRC, GST_PAD_ALWAYS, GST_CAPS_NEW ( "example_src", "unknown/unknown", NULL ) ); /* A number of functon prototypes are given so we can refer to them later. */ static void gst_example_class_init (GstExampleClass *klass); static void gst_example_init (GstExample *example); static void gst_example_chain (GstPad *pad, GstData *_data); static void gst_example_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec); static void gst_example_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec); static GstElementStateReturn gst_example_change_state (GstElement *element); /* The parent class pointer needs to be kept around for some object * operations. */ static GstElementClass *parent_class = NULL; /* This array holds the ids of the signals registered for this object. * The array indexes are based on the enum up above. */ static guint gst_example_signals[LAST_SIGNAL] = { 0 }; /* This function is used to register and subsequently return the type * identifier for this object class. On first invocation, it will * register the type, providing the name of the class, struct sizes, * and pointers to the various functions that define the class. */ GType gst_example_get_type(void) { static GType example_type = 0; if (!example_type) { static const GTypeInfo example_info = { sizeof(GstExampleClass), NULL, NULL, (GClassInitFunc)gst_example_class_init, NULL, NULL, sizeof(GstExample), 0, (GInstanceInitFunc)gst_example_init, }; example_type = g_type_register_static(GST_TYPE_ELEMENT, "GstExample", &example_info, 0); } return example_type; } /* In order to create an instance of an object, the class must be * initialized by this function. GObject will take care of running * it, based on the pointer to the function provided above. */ static void gst_example_class_init (GstExampleClass *klass) { /* Class pointers are needed to supply pointers to the private * implementations of parent class methods. */ GObjectClass *gobject_class; GstElementClass *gstelement_class; /* Since the example class contains the parent classes, you can simply * cast the pointer to get access to the parent classes. */ gobject_class = (GObjectClass*)klass; gstelement_class = (GstElementClass*)klass; /* The parent class is needed for class method overrides. */ parent_class = g_type_class_ref(GST_TYPE_ELEMENT); /* Here we add an argument to the object. This argument is an integer, * and can be both read and written. */ g_object_class_install_property(G_OBJECT_CLASS(klass), ARG_ACTIVE, g_param_spec_int("active","active","active", G_MININT,G_MAXINT,0,G_PARAM_READWRITE)); /* CHECKME */ /* Here we add a signal to the object. This is avery useless signal * called asdf. The signal will also pass a pointer to the listeners * which happens to be the example element itself */ gst_example_signals[ASDF] = g_signal_new("asdf", G_TYPE_FROM_CLASS(klass), G_SIGNAL_RUN_LAST, G_STRUCT_OFFSET (GstExampleClass, asdf), NULL, NULL, g_cclosure_marshal_VOID__POINTER, G_TYPE_NONE, 1, GST_TYPE_EXAMPLE); /* The last thing is to provide the functions that implement get and set * of arguments. */ gobject_class->set_property = gst_example_set_property; gobject_class->get_property = gst_example_get_property; /* we also override the default state change handler with our own * implementation */ gstelement_class->change_state = gst_example_change_state; } /* This function is responsible for initializing a specific instance of * the plugin. */ static void gst_example_init(GstExample *example) { /* First we create the sink pad, which is the input to the element. * We will use the template constructed by the factory. */ example->sinkpad = gst_pad_new_from_template ( GST_PAD_TEMPLATE_GET (sink_factory), "sink"); /* Setting the chain function allows us to supply the function that will * actually be performing the work. Without this, the element would do * nothing, with undefined results (assertion failures and such). */ gst_pad_set_chain_function(example->sinkpad,gst_example_chain); /* We then must add this pad to the element's list of pads. The base * element class manages the list of pads, and provides accessors to it. */ gst_element_add_pad(GST_ELEMENT(example),example->sinkpad); /* The src pad, the output of the element, is created and registered * in the same way, with the exception of the chain function. Source * pads don't have chain functions, because they can't accept buffers, * they only produce them. */ example->srcpad = gst_pad_new_from_template ( GST_PAD_TEMPLATE_GET (src_factory), "src"); gst_element_add_pad(GST_ELEMENT(example),example->srcpad); /* Initialization of element's private variables. */ example->active = FALSE; } /* The chain function is the heart of the element. It's where all the * work is done. It is passed a pointer to the pad in question, as well * as the buffer provided by the peer element. */ static void gst_example_chain (GstPad *pad, GstData *_data) { GstBuffer *buf = GST_BUFFER (_data); GstExample *example; GstBuffer *outbuf; /* Some of these checks are of dubious value, since if there were not * already true, the chain function would never be called. */ g_return_if_fail(pad != NULL); g_return_if_fail(GST_IS_PAD(pad)); g_return_if_fail(buf != NULL); /* We need to get a pointer to the element this pad belogs to. */ example = GST_EXAMPLE(gst_pad_get_parent (pad)); /* A few more sanity checks to make sure that the element that owns * this pad is the right kind of element, in case something got confused. */ g_return_if_fail(example != NULL); g_return_if_fail(GST_IS_EXAMPLE(example)); /* If we are supposed to be doing something, here's where it happens. */ if (example->active) { /* In this example we're going to copy the buffer to another one, * so we need to allocate a new buffer first. */ outbuf = gst_buffer_new(); /* We need to copy the size and offset of the buffer at a minimum. */ GST_BUFFER_SIZE (outbuf) = GST_BUFFER_SIZE (buf); GST_BUFFER_OFFSET (outbuf) = GST_BUFFER_OFFSET (buf); /* Then allocate the memory for the new buffer */ GST_BUFFER_DATA (outbuf) = (guchar *)g_malloc (GST_BUFFER_SIZE (outbuf)); /* Then copy the data in the incoming buffer into the new buffer. */ memcpy (GST_BUFFER_DATA (outbuf), GST_BUFFER_DATA (buf), GST_BUFFER_SIZE (outbuf)); /* we don't need the incomming buffer anymore so we unref it. When we are * the last plugin with a handle to the buffer, its memory will be freed */ gst_buffer_unref (buf); /* When we're done with the buffer, we push it on to the next element * in the pipeline, through the element's source pad, which is stored * in the element's structure. */ gst_pad_push(example->srcpad,GST_DATA (outbuf)); /* For fun we'll emit our useless signal here */ g_signal_emit(G_OBJECT (example), gst_example_signals[ASDF], 0, example); /* If we're not doing something, just send the original incoming buffer. */ } else { gst_pad_push(example->srcpad,GST_DATA (buf)); } } /* Arguments are part of the Gtk+ object system, and these functions * enable the element to respond to various arguments. */ static void gst_example_set_property (GObject *object, guint prop_id, const GValue *value, GParamSpec *pspec) { GstExample *example; /* It's not null if we got it, but it might not be ours */ g_return_if_fail(GST_IS_EXAMPLE(object)); /* Get a pointer of the right type. */ example = GST_EXAMPLE(object); /* Check the argument id to see which argument we're setting. */ switch (prop_id) { case ARG_ACTIVE: /* Here we simply copy the value of the argument to our private * storage. More complex operations can be done, but beware that * they may occur at any time, possibly even while your chain function * is running, if you are using threads. */ example->active = g_value_get_int (value); g_print("example: set active to %d\n",example->active); break; default: break; } } /* The set function is simply the inverse of the get fuction. */ static void gst_example_get_property (GObject *object, guint prop_id, GValue *value, GParamSpec *pspec) { GstExample *example; /* It's not null if we got it, but it might not be ours */ g_return_if_fail(GST_IS_EXAMPLE(object)); example = GST_EXAMPLE(object); switch (prop_id) { case ARG_ACTIVE: g_value_set_int (value, example->active); break; default: G_OBJECT_WARN_INVALID_PROPERTY_ID (object, prop_id, pspec); break; } } /* This is the state change function that will be called when * the element goes through the different state changes. * The plugin can prepare itself and its internal data structures * in the various state transitions. */ static GstElementStateReturn gst_example_change_state (GstElement *element) { GstExample *example; /* cast to our plugin */ example = GST_EXAMPLE(element); /* we perform our actions based on the state transition * of the element */ switch (GST_STATE_TRANSITION (element)) { /* The NULL to READY transition is used to * create threads (if any) */ case GST_STATE_NULL_TO_READY: break; /* In the READY to PAUSED state, the element should * open devices (if any) */ case GST_STATE_READY_TO_PAUSED: break; /* In the PAUSED to PLAYING state, the element should * prepare itself for operation or continue after a PAUSE */ case GST_STATE_PAUSED_TO_PLAYING: break; /* In the PLAYING to PAUSED state, the element should * PAUSE itself and make sure it can resume operation */ case GST_STATE_PLAYING_TO_PAUSED: break; /* In the PAUSED to READY state, the element should reset * its internal state and close any devices. */ case GST_STATE_PAUSED_TO_READY: break; /* The element should free all resources, terminate threads * and put itself into its initial state again */ case GST_STATE_READY_TO_NULL: break; } /* Then we call the parent state change handler */ return parent_class->change_state (element); } /* This is the entry into the plugin itself. When the plugin loads, * this function is called to register everything that the plugin provides. */ static gboolean plugin_init (GModule *module, GstPlugin *plugin) { GstElementFactory *factory; /* We need to create an ElementFactory for each element we provide. * This consists of the name of the element, the GType identifier, * and a pointer to the details structure at the top of the file. */ factory = gst_element_factory_new("example", GST_TYPE_EXAMPLE, &example_details); g_return_val_if_fail(factory != NULL, FALSE); /* The pad templates can be easily generated from the factories above, * and then added to the list of padtemplates for the elementfactory. */ gst_element_factory_add_pad_template (factory, GST_PAD_TEMPLATE_GET (sink_factory)); gst_element_factory_add_pad_template (factory, GST_PAD_TEMPLATE_GET (src_factory)); /* The very last thing is to register the elementfactory with the plugin. */ gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory)); /* Now we can return successfully. */ return TRUE; /* At this point, the GStreamer core registers the plugin, its * elementfactories, padtemplates, etc., for use in you application. */ } /* This structure describes the plugin to the system for dynamically loading * plugins, so that the version number and name can be checked in a uniform * way. * * The symbol pointing to this structure is the only symbol looked up when * loading the plugin. */ GstPluginDesc plugin_desc = { GST_VERSION_MAJOR, /* The major version of the core that this was built with */ GST_VERSION_MINOR, /* The minor version of the core that this was built with */ "example", /* The name of the plugin. This must be unique: plugins with * the same name will be assumed to be identical, and only * one will be loaded. */ plugin_init /* Pointer to the initialisation function for the plugin. */ };