gstreamer/gst/gsttypefind.c

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/* GStreamer
* Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
*
* gsttypefind.h: typefinding subsystem
*
* 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.
*/
/**
* SECTION:gsttypefind
* @short_description: Stream type detection
*
*/
/**
* SECTION:gsttypefindfactory
* @short_description: Information about registered typefind functions
*
* These functions allow querying informations about registered typefind
* functions. How to create and register these functions is described in
* the section <link linkend="gstreamer-Writing-typefind-functions">
* "Writing typefind functions"</link>.
*
* <example>
* <title>how to write a simple typefinder</title>
* <programlisting>
* typedef struct {
* guint8 *data;
* guint size;
* guint probability;
* GstCaps *data;
* } MyTypeFind;
* static void
* my_peek (gpointer data, gint64 offset, guint size)
* {
* MyTypeFind *find = (MyTypeFind *) data;
* if (offset &gt;= 0 &amp;&amp; offset + size &lt;= find->size) {
* return find->data + offset;
* }
* return NULL;
* }
* static void
* my_suggest (gpointer data, guint probability, GstCaps *caps)
* {
* MyTypeFind *find = (MyTypeFind *) data;
* if (probability &gt; find->probability) {
* find->probability = probability;
* gst_caps_replace (&amp;find->caps, caps);
* }
* }
* static GstCaps *
* find_type (guint8 *data, guint size)
* {
* GList *walk, *type_list;
* MyTypeFind find = {data, size, 0, NULL};
* GstTypeFind gst_find = {my_peek, my_suggest, &amp;find, };
*
* walk = type_list = gst_type_find_factory_get_list ();
* while (walk) {
* GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (walk->data);
* walk = g_list_next (walk)
* gst_type_find_factory_call_function (factory, &amp;gst_find);
* }
* g_list_free (type_list);
* return find.caps;
* };
* </programlisting>
* </example>
*
* The above example shows how to write a very simple typefinder that identifies
* the given data. You can get quite a bit more complicated than that though.
*/
#include "gst_private.h"
#include "gstinfo.h"
#include "gsttypefind.h"
#include "gstregistrypool.h"
GST_DEBUG_CATEGORY_STATIC (gst_type_find_debug);
#define GST_CAT_DEFAULT gst_type_find_debug
static void gst_type_find_factory_class_init (gpointer g_class,
gpointer class_data);
static void gst_type_find_factory_init (GTypeInstance * instance,
gpointer g_class);
static void gst_type_find_factory_dispose (GObject * object);
static void gst_type_find_factory_unload_thyself (GstPluginFeature * feature);
static void gst_type_find_load_plugin (GstTypeFind * find, gpointer data);
static GstPluginFeatureClass *parent_class = NULL;
GType
gst_type_find_factory_get_type (void)
{
static GType typefind_type = 0;
if (!typefind_type) {
static const GTypeInfo typefind_info = {
sizeof (GstTypeFindFactoryClass),
NULL,
NULL,
gst_type_find_factory_class_init,
NULL,
NULL,
sizeof (GstTypeFindFactory),
0,
gst_type_find_factory_init,
NULL
};
typefind_type = g_type_register_static (GST_TYPE_PLUGIN_FEATURE,
"GstTypeFindFactory", &typefind_info, 0);
GST_DEBUG_CATEGORY_INIT (gst_type_find_debug, "GST_TYPEFIND",
GST_DEBUG_FG_GREEN, "typefinding subsystem");
}
return typefind_type;
}
static void
gst_type_find_factory_class_init (gpointer g_class, gpointer class_data)
{
GstPluginFeatureClass *gstpluginfeature_class =
GST_PLUGIN_FEATURE_CLASS (g_class);
GObjectClass *object_class = G_OBJECT_CLASS (g_class);
parent_class = g_type_class_peek_parent (g_class);
object_class->dispose = gst_type_find_factory_dispose;
gstpluginfeature_class->unload_thyself =
GST_DEBUG_FUNCPTR (gst_type_find_factory_unload_thyself);
}
static void
gst_type_find_factory_init (GTypeInstance * instance, gpointer g_class)
{
GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (instance);
factory->user_data = factory;
factory->function = gst_type_find_load_plugin;
}
static void
gst_type_find_factory_dispose (GObject * object)
{
GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (object);
if (factory->caps) {
gst_caps_unref (factory->caps);
factory->caps = NULL;
}
if (factory->extensions) {
g_strfreev (factory->extensions);
factory->extensions = NULL;
}
}
static void
gst_type_find_factory_unload_thyself (GstPluginFeature * feature)
{
GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (feature);
factory->function = gst_type_find_load_plugin;
factory->user_data = factory;
}
static void
gst_type_find_load_plugin (GstTypeFind * find, gpointer data)
{
GstTypeFindFactory *factory = GST_TYPE_FIND_FACTORY (data);
GST_DEBUG_OBJECT (factory, "need to load typefind function %s",
GST_PLUGIN_FEATURE_NAME (factory));
if (gst_plugin_feature_ensure_loaded (GST_PLUGIN_FEATURE (factory))) {
if (factory->function == gst_type_find_load_plugin) {
/* looks like we didn't get a real typefind function */
g_warning ("could not load valid typefind function for feature '%s'\n",
GST_PLUGIN_FEATURE_NAME (factory));
} else {
g_assert (factory->function);
gst_type_find_factory_call_function (factory, find);
}
}
}
/**
* gst_type_find_factory_get_list:
*
* Gets the list of all registered typefind factories. You must free the
* list using g_list_free.
*
* Returns: the list of all registered typefind factories
*/
GList *
gst_type_find_factory_get_list (void)
{
return gst_registry_pool_feature_list (GST_TYPE_TYPE_FIND_FACTORY);
}
/**
* gst_type_find_factory_get_caps:
* @factory: a factory
*
* Gets the caps associated with a typefind factory.
*
* Returns: the #GstCaps associated with this factory
*/
const GstCaps *
gst_type_find_factory_get_caps (const GstTypeFindFactory * factory)
{
g_return_val_if_fail (GST_IS_TYPE_FIND_FACTORY (factory), NULL);
return factory->caps;
}
/**
* gst_type_find_factory_get_extensions:
* @factory: a factory
*
* Gets the extensions associated with a typefind factory. The returned
* array should not be changed. If you need to change stuff in it, you should
* copy it using g_stdupv(). This function may return NULL to indicate
* a 0-length list.
*
* Returns: a NULL-terminated array of extensions associated with this factory
*/
gchar **
gst_type_find_factory_get_extensions (const GstTypeFindFactory * factory)
{
g_return_val_if_fail (GST_IS_TYPE_FIND_FACTORY (factory), NULL);
return factory->extensions;
}
/**
* gst_type_find_factory_call_function:
* @factory: a factory
* @find: a properly setup #GstTypeFind entry. The get_data and suggest_type
* members must be set.
*
* Calls the typefinding function associated with this factory.
*/
void
gst_type_find_factory_call_function (const GstTypeFindFactory * factory,
GstTypeFind * find)
{
g_return_if_fail (GST_IS_TYPE_FIND_FACTORY (factory));
g_return_if_fail (find != NULL);
g_return_if_fail (find->peek != NULL);
g_return_if_fail (find->suggest != NULL);
/* should never happen */
g_assert (factory->function != NULL);
factory->function (find, factory->user_data);
}
/**
* gst_type_find_register:
* @plugin: the GstPlugin to register with
* @name: the name for registering
* @rank: rank (or importance) of this typefind function
* @func: the function to use for typefinding
* @extensions: optional extensions that could belong to this type
* @possible_caps: optionally the caps that could be returned when typefinding succeeds
* @data: optional user data. This user data must be available until the plugin
* is unloaded.
*
* Registers a new typefind function to be used for typefinding. After
* registering this function will be available for typefinding.
* This function is typically called during an element's plugin initialization.
*
* Returns: TRUE on success, FALSE otherwise
*/
gboolean
gst_type_find_register (GstPlugin * plugin, const gchar * name, guint rank,
GstTypeFindFunction func, gchar ** extensions,
const GstCaps * possible_caps, gpointer data)
{
GstTypeFindFactory *factory;
g_return_val_if_fail (plugin != NULL, FALSE);
g_return_val_if_fail (name != NULL, FALSE);
g_return_val_if_fail (func != NULL, FALSE);
GST_INFO ("registering typefind function for %s", name);
factory =
GST_TYPE_FIND_FACTORY (gst_registry_pool_find_feature (name,
GST_TYPE_TYPE_FIND_FACTORY));
if (!factory) {
factory = g_object_new (GST_TYPE_TYPE_FIND_FACTORY, NULL);
GST_DEBUG_OBJECT (factory, "using new typefind factory for %s", name);
g_assert (GST_IS_TYPE_FIND_FACTORY (factory));
gst_plugin_feature_set_name (GST_PLUGIN_FEATURE (factory), name);
gst_plugin_add_feature (plugin, GST_PLUGIN_FEATURE (factory));
} else {
GST_DEBUG_OBJECT (factory, "using old typefind factory for %s", name);
}
gst_plugin_feature_set_rank (GST_PLUGIN_FEATURE (factory), rank);
if (factory->extensions)
g_strfreev (factory->extensions);
factory->extensions = g_strdupv (extensions);
gst_caps_replace (&factory->caps, (GstCaps *) possible_caps);
factory->function = func;
factory->user_data = data;
return TRUE;
}
/*** typefind function interface **********************************************/
/**
* gst_type_find_peek:
* @find: the find object the function was called with
* @offset: the offset
* @size: the number of bytes to return
*
* Returns size bytes of the stream to identify beginning at offset. If offset
* is a positive number, the offset is relative to the beginning of the stream,
* if offset is a negative number the offset is relative to the end of the
* stream. The returned memory is valid until the typefinding function returns
* and must not be freed.
* If NULL is returned, that data is not available.
*
* Returns: the requested data or NULL if that data is not available.
*/
guint8 *
gst_type_find_peek (GstTypeFind * find, gint64 offset, guint size)
{
g_return_val_if_fail (find->peek != NULL, NULL);
return find->peek (find->data, offset, size);
}
/**
* gst_type_find_suggest:
* @find: the find object the function was called with
* @probability: the probability in percent that the suggestion is right
* @caps: the fixed caps to suggest
*
* If a typefind function calls this function it suggests the caps with the
* given probability. A typefind function may supply different suggestions
* in one call.
* It is up to the caller of the typefind function to interpret these values.
*/
void
gst_type_find_suggest (GstTypeFind * find, guint probability,
const GstCaps * caps)
{
g_return_if_fail (find->suggest != NULL);
g_return_if_fail (probability <= 100);
g_return_if_fail (caps != NULL);
g_return_if_fail (gst_caps_is_fixed (caps));
find->suggest (find->data, probability, caps);
}
/**
* gst_type_find_get_length:
* @find: the find object the function was called with
*
* Get the length of the data stream.
*
* Returns: the length of the data stream or 0 if it is not available.
*/
guint64
gst_type_find_get_length (GstTypeFind * find)
{
if (find->get_length == NULL)
return 0;
return find->get_length (find->data);
}