gstreamer/gst/gsttypefind.c

/* GStreamer
 * Copyright (C) 2003 Benjamin Otte <in7y118@public.uni-hamburg.de>
 *
 * gsttypefind.c: 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
 *
 */

#include "gst_private.h"
#include "gstinfo.h"
#include "gsttypefind.h"
#include "gsttypefindfactory.h"
#include "gstregistrypool.h"

GST_DEBUG_CATEGORY_EXTERN (gst_type_find_debug);
#define GST_CAT_DEFAULT gst_type_find_debug

/**
 * 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);
}