gstreamer/gst/playback/gstfactorylists.c

/* GStreamer
 * Copyright (C) <2007> Wim Taymans <wim.taymans@gmail.com>
 *
 * 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.
 */
#include <string.h>

#include "gstfactorylists.h"

/* function used to sort element features. We first sort on the rank, then
 * on the element name (to get a consistent, predictable list) */
static gint
compare_ranks (GValue * v1, GValue * v2)
{
  gint diff;
  const gchar *rname1, *rname2;
  GstPluginFeature *f1, *f2;

  f1 = g_value_get_object (v1);
  f2 = g_value_get_object (v2);

  diff = gst_plugin_feature_get_rank (f2) - gst_plugin_feature_get_rank (f1);
  if (diff != 0)
    return diff;

  rname1 = gst_plugin_feature_get_name (f1);
  rname2 = gst_plugin_feature_get_name (f2);

  diff = strcmp (rname2, rname1);

  return diff;
}

#if 0
static void
print_feature (GstPluginFeature * feature)
{
  const gchar *rname;

  rname = gst_plugin_feature_get_name (feature);

  GST_DEBUG ("%s", rname);
}
#endif

/* get a filtered feature list as a GValueArray */
static GValueArray *
get_feature_array (GstPluginFeatureFilter filter)
{
  GValueArray *result;
  GList *walk, *list;

  result = g_value_array_new (0);

  /* get the feature list using the filter */
  list = gst_default_registry_feature_filter (filter, FALSE, NULL);

  /* convert to an array */
  for (walk = list; walk; walk = g_list_next (walk)) {
    GstElementFactory *factory = GST_ELEMENT_FACTORY (walk->data);
    GValue val = { 0, };

    g_value_init (&val, G_TYPE_OBJECT);
    g_value_set_object (&val, factory);
    g_value_array_append (result, &val);
    g_value_unset (&val);
  }
  gst_plugin_feature_list_free (list);

  /* sort on rank and name */
  g_value_array_sort (result, (GCompareFunc) compare_ranks);

  return result;
}

/* the filter function for selecting the elements we can use in
 * autoplugging */
static gboolean
decoders_filter (GstPluginFeature * feature)
{
  guint rank;
  const gchar *klass;

  /* we only care about element factories */
  if (!GST_IS_ELEMENT_FACTORY (feature))
    return FALSE;

  klass = gst_element_factory_get_klass (GST_ELEMENT_FACTORY (feature));
  /* only demuxers, decoders, depayloaders and parsers can play */
  if (strstr (klass, "Demux") == NULL &&
      strstr (klass, "Decoder") == NULL &&
      strstr (klass, "Depayloader") == NULL &&
      strstr (klass, "Parse") == NULL) {
    return FALSE;
  }

  /* only select elements with autoplugging rank */
  rank = gst_plugin_feature_get_rank (feature);
  if (rank < GST_RANK_MARGINAL)
    return FALSE;

  return TRUE;
}

/* the filter function for selecting the elements we can use in
 * autoplugging */
static gboolean
sinks_filter (GstPluginFeature * feature)
{
  guint rank;
  const gchar *klass;

  /* we only care about element factories */
  if (!GST_IS_ELEMENT_FACTORY (feature))
    return FALSE;

  klass = gst_element_factory_get_klass (GST_ELEMENT_FACTORY (feature));
  /* only sinks can play */
  if (strstr (klass, "Sink") == NULL) {
    return FALSE;
  }

  /* must be audio or video sink */
  if (strstr (klass, "Audio") == NULL && strstr (klass, "Video") == NULL) {
    return FALSE;
  }

  /* only select elements with autoplugging rank */
  rank = gst_plugin_feature_get_rank (feature);
  if (rank < GST_RANK_MARGINAL)
    return FALSE;

  return TRUE;
}


/**
 * gst_factory_list_get_decoders:
 *
 * Get a sorted list of factories that can be used in decoding pipelines.
 *
 * Returns: a #GValueArray of #GstElementFactory elements. Use
 * g_value_array_free() after usage.
 */
GValueArray *
gst_factory_list_get_decoders (void)
{
  GValueArray *result;

  /* first filter out the interesting element factories */
  result = get_feature_array ((GstPluginFeatureFilter) decoders_filter);

  return result;
}

/**
 * gst_factory_list_get_sinks:
 *
 * Get a sorted list of factories that can be used as sinks in a decoding
 * pipeline.
 *
 * Returns: a #GValueArray of #GstElementFactory elements. Use
 * g_value_array_free() after usage.
 */
GValueArray *
gst_factory_list_get_sinks (void)
{
  GValueArray *result;

  /* first filter out the interesting element factories */
  result = get_feature_array ((GstPluginFeatureFilter) sinks_filter);

  return result;
}

/**
 * gst_factory_list_filter:
 * @array: a #GValueArray to filter
 * @caps: a #GstCaps
 *
 * Filter out all the elementfactories in @array that can handle @caps as
 * input.
 *
 * Returns: a #GValueArray of #GstElementFactory elements. Use
 * g_value_array_free() after usage.
 */
GValueArray *
gst_factory_list_filter (GValueArray * array, const GstCaps * caps)
{
  GValueArray *result;
  gint i;

  result = g_value_array_new (0);

  GST_DEBUG ("finding factories");

  /* loop over all the factories */
  for (i = 0; i < array->n_values; i++) {
    GValue *value;
    GstElementFactory *factory;
    const GList *templates;
    GList *walk;

    value = g_value_array_get_nth (array, i);
    factory = g_value_get_object (value);

    /* get the templates from the element factory */
    templates = gst_element_factory_get_static_pad_templates (factory);
    for (walk = (GList *) templates; walk; walk = g_list_next (walk)) {
      GstStaticPadTemplate *templ = walk->data;

      /* we only care about the sink templates */
      if (templ->direction == GST_PAD_SINK) {
        GstCaps *intersect;
        GstCaps *tmpl_caps;

        /* try to intersect the caps with the caps of the template */
        tmpl_caps = gst_static_caps_get (&templ->static_caps);

        /* FIXME, intersect is not the right method, we ideally want to check
         * for a subset here */
        intersect = gst_caps_intersect (caps, tmpl_caps);
        gst_caps_unref (tmpl_caps);

        /* check if the intersection is empty */
        if (!gst_caps_is_empty (intersect)) {
          /* non empty intersection, we can use this element */
          GValue resval = { 0, };
          g_value_init (&resval, G_TYPE_OBJECT);
          g_value_set_object (&resval, factory);
          g_value_array_append (result, &resval);
          g_value_unset (&resval);
          gst_caps_unref (intersect);
          break;
        }
        gst_caps_unref (intersect);
      }
    }
  }
  return result;
}