gstreamer/gst/gstprotection.c
Alex Ashley abdafb0d64 protection: add GstProtectionMeta to support protected content
In order to support some types of protected streams (such as those
protected using DASH Common Encryption) some per-buffer information
needs to be passed between elements.

This commit adds a GstMeta type called GstProtectionMeta that allows
protection specific information to be added to a GstBuffer. An example
of its usage is qtdemux providing information to each output sample
that enables a downstream element to decrypt it.

This commit adds a utility function to select a supported protection
system from the installed Decryption elements found in the registry.
The gst_protection_select_system function that takes an array of
identifiers and searches the registry for a element of klass Decryptor that
supports one or more of the supplied identifiers. If multiple elements
are found, the one with the highest rank is selected.

This commit adds a unit test for the gst_protection_select_system
function that adds a fake Decryptor element to the registry and then
checks that it can correctly be selected by the utility function.

This commit adds a unit test for GstProtectionMeta that creates
GstProtectionMeta and adds & removes it from a buffer and performs some
simple reference count checks.

API: gst_buffer_add_protection_meta()
API: gst_buffer_get_protection_meta()
API: gst_protection_select_system()
API: gst_protection_meta_api_get_type()
API: gst_protection_meta_get_info()

https://bugzilla.gnome.org/show_bug.cgi?id=705991
2015-04-18 12:24:06 +01:00

209 lines
6.5 KiB
C

/* GStreamer
* Copyright (C) <2013> YouView TV Ltd.
*
* 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., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
/**
* SECTION:gstprotection
* @short_description: Functions and classes to support encrypted streams.
*
* The GstProtectionMeta class enables the information needed to decrypt a
* #GstBuffer to be attached to that buffer.
*
* Typically, a demuxer element would attach GstProtectionMeta objects
* to the buffers that it pushes downstream. The demuxer would parse the
* protection information for a video/audio frame from its input data and use
* this information to populate the #GstStructure @info field,
* which is then encapsulated in a GstProtectionMeta object and attached to
* the corresponding output buffer using the gst_buffer_add_protection_meta()
* function. The information in this attached GstProtectionMeta would be
* used by a downstream decrypter element to recover the original unencrypted
* frame.
*
* Since: 1.6
*/
#include "gst_private.h"
#include "glib-compat-private.h"
#include "gstprotection.h"
#define GST_CAT_DEFAULT GST_CAT_PROTECTION
static gboolean gst_protection_meta_init (GstMeta * meta, gpointer params,
GstBuffer * buffer);
static void gst_protection_meta_free (GstMeta * meta, GstBuffer * buffer);
static const gchar *gst_protection_factory_check (GstElementFactory * fact,
const gchar ** system_identifiers);
GType
gst_protection_meta_api_get_type (void)
{
static volatile GType type;
static const gchar *tags[] = { NULL };
if (g_once_init_enter (&type)) {
GType _type = gst_meta_api_type_register ("GstProtectionMetaAPI", tags);
g_once_init_leave (&type, _type);
}
return type;
}
static gboolean
gst_protection_meta_init (GstMeta * meta, gpointer params, GstBuffer * buffer)
{
GstProtectionMeta *protection_meta = (GstProtectionMeta *) meta;
protection_meta->info = NULL;
return TRUE;
}
static void
gst_protection_meta_free (GstMeta * meta, GstBuffer * buffer)
{
GstProtectionMeta *protection_meta = (GstProtectionMeta *) meta;
if (protection_meta->info)
gst_structure_free (protection_meta->info);
}
const GstMetaInfo *
gst_protection_meta_get_info (void)
{
static const GstMetaInfo *protection_meta_info = NULL;
if (g_once_init_enter (&protection_meta_info)) {
const GstMetaInfo *meta =
gst_meta_register (GST_PROTECTION_META_API_TYPE, "GstProtectionMeta",
sizeof (GstProtectionMeta), gst_protection_meta_init,
gst_protection_meta_free,
(GstMetaTransformFunction) NULL);
g_once_init_leave (&protection_meta_info, meta);
}
return protection_meta_info;
}
/**
* gst_buffer_add_protection_meta:
* @buffer: #GstBuffer holding an encrypted sample, to which protection
* metadata should be added.
* @info: (transfer full): a #GstStructure holding cryptographic
* information relating to the sample contained in @buffer. This
* function takes ownership of @info.
*
* Attaches protection metadata to a #GstBuffer.
*
* Returns: a pointer to the added #GstProtectionMeta if successful; %NULL if
* unsuccessful.
*
* Since: 1.6
*/
GstProtectionMeta *
gst_buffer_add_protection_meta (GstBuffer * buffer, GstStructure * info)
{
GstProtectionMeta *meta;
g_return_val_if_fail (GST_IS_BUFFER (buffer), NULL);
g_return_val_if_fail (info != NULL, NULL);
meta =
(GstProtectionMeta *) gst_buffer_add_meta (buffer,
GST_PROTECTION_META_INFO, NULL);
meta->info = info;
return meta;
}
/**
* gst_protection_select_system:
* @system_identifiers: (transfer none): A null terminated array of strings
* that contains the UUID values of each protection system that is to be
* checked.
*
* Iterates the supplied list of UUIDs and checks the GstRegistry for
* an element that supports one of the supplied UUIDs. If more than one
* element matches, the system ID of the highest ranked element is selected.
*
* Returns: (transfer none): One of the strings from @system_identifiers that
* indicates the highest ranked element that implements the protection system
* indicated by that system ID, or %NULL if no element has been found.
*
* Since: 1.6
*/
const gchar *
gst_protection_select_system (const gchar ** system_identifiers)
{
GList *decryptors, *walk;
const gchar *retval = NULL;
decryptors =
gst_element_factory_list_get_elements (GST_ELEMENT_FACTORY_TYPE_DECRYPTOR,
GST_RANK_MARGINAL);
for (walk = decryptors; !retval && walk; walk = g_list_next (walk)) {
GstElementFactory *fact = (GstElementFactory *) walk->data;
retval = gst_protection_factory_check (fact, system_identifiers);
}
gst_plugin_feature_list_free (decryptors);
return retval;
}
static const gchar *
gst_protection_factory_check (GstElementFactory * fact,
const gchar ** system_identifiers)
{
const GList *template, *walk;
const gchar *retval = NULL;
template = gst_element_factory_get_static_pad_templates (fact);
for (walk = template; walk && !retval; walk = g_list_next (walk)) {
GstStaticPadTemplate *templ = walk->data;
GstCaps *caps = gst_static_pad_template_get_caps (templ);
guint leng = gst_caps_get_size (caps);
for (guint i = 0; !retval && i < leng; ++i) {
GstStructure *st;
st = gst_caps_get_structure (caps, i);
if (gst_structure_has_field_typed (st, PROTECTION_SYSTEM_ID_CAPS_FIELD,
G_TYPE_STRING)) {
const gchar *sys_id =
gst_structure_get_string (st, PROTECTION_SYSTEM_ID_CAPS_FIELD);
GST_DEBUG ("Found decryptor that supports protection system %s",
sys_id);
for (guint j = 0; !retval && system_identifiers[j]; ++j) {
GST_TRACE (" compare with %s", system_identifiers[j]);
if (g_ascii_strcasecmp (system_identifiers[j], sys_id) == 0) {
GST_DEBUG (" Selecting %s", system_identifiers[j]);
retval = system_identifiers[j];
}
}
}
}
gst_caps_unref (caps);
}
return retval;
}