gstreamer/subprojects/gst-plugins-base/gst-libs/gst/video/gstvideocodecalphameta.c

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/* GStreamer
* Copyright (C) 2021 Collabora Ltd.
* Author: Nicolas Dufresne <nicolas.dufresne@collabora.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., 51 Franklin St, Fifth Floor,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include "gstvideocodecalphameta.h"
/**
* SECTION:gstvideocodecalphameta
* @title: GstVideoCodecAlphaMeta
* @short_description: GstMeta that can carry an extra buffer holding an
* encoded a frame whith luma that can be used as an alpha channel.
*
* This meta is primarily for internal use in GStreamer elements to support
* VP8/VP9 transparent video stored into WebM or Matroska containers, or
* transparent static AV1 images. Nothing prevents you from using this meta
* for custom purposes, but it generally can't be used to easily to add support
* for alpha channels to CODECs or formats that don't support that out of the
* box.
*
* Since: 1.20
*/
/**
* gst_video_codec_alpha_meta_api_get_type:
*
* Returns: #GType for the #GstVideoCodecAlphaMeta structure.
*
* Since: 1.20
*/
GType
gst_video_codec_alpha_meta_api_get_type (void)
{
static GType type = 0;
static const gchar *tags[] = { GST_META_TAG_VIDEO_STR, NULL };
if (g_once_init_enter (&type)) {
GType _type =
gst_meta_api_type_register ("GstVideoCodecAlphaMetaAPI", tags);
g_once_init_leave (&type, _type);
}
return type;
}
static gboolean
gst_video_codec_alpha_meta_transform (GstBuffer * dest,
GstMeta * meta, GstBuffer * buffer, GQuark type, gpointer data)
{
GstVideoCodecAlphaMeta *dmeta, *smeta;
smeta = (GstVideoCodecAlphaMeta *) meta;
if (GST_META_TRANSFORM_IS_COPY (type)) {
dmeta =
(GstVideoCodecAlphaMeta *) gst_buffer_add_meta (dest,
GST_VIDEO_CODEC_ALPHA_META_INFO, NULL);
if (!dmeta)
return FALSE;
dmeta->buffer = gst_buffer_ref (smeta->buffer);
}
return TRUE;
}
static gboolean
gst_video_codec_alpha_meta_init (GstMeta * meta, gpointer params,
GstBuffer * buffer)
{
GstVideoCodecAlphaMeta *ca_meta = (GstVideoCodecAlphaMeta *) meta;
/* the buffer ownership is transfered to the Meta */
ca_meta->buffer = (GstBuffer *) params;
return TRUE;
}
static void
gst_video_codec_alpha_meta_free (GstMeta * meta, GstBuffer * buffer)
{
GstVideoCodecAlphaMeta *ca_meta = (GstVideoCodecAlphaMeta *) meta;
gst_clear_buffer (&ca_meta->buffer);
}
/**
* gst_video_codec_alpha_meta_get_info:
*
* Returns: #GstMetaInfo pointer that describes #GstVideoCodecAlphaMeta.
*
* Since: 1.20
*/
const GstMetaInfo *
gst_video_codec_alpha_meta_get_info (void)
{
static const GstMetaInfo *info = NULL;
if (g_once_init_enter ((GstMetaInfo **) & info)) {
const GstMetaInfo *meta =
gst_meta_register (GST_VIDEO_CODEC_ALPHA_META_API_TYPE,
"GstVideoCodecAlphaMeta",
sizeof (GstVideoCodecAlphaMeta),
gst_video_codec_alpha_meta_init,
gst_video_codec_alpha_meta_free,
gst_video_codec_alpha_meta_transform);
g_once_init_leave ((GstMetaInfo **) & info, (GstMetaInfo *) meta);
}
return info;
}
/**
* gst_buffer_add_video_codec_alpha_meta:
* @buffer: (transfer none): a #GstBuffer
* @alpha_buffer: (transfer full): a #GstBuffer
*
* Attaches a #GstVideoCodecAlphaMeta metadata to @buffer with
* the given alpha buffer.
*
* Returns: (transfer none): the #GstVideoCodecAlphaMeta on @buffer.
*
* Since: 1.20
*/
GstVideoCodecAlphaMeta *
gst_buffer_add_video_codec_alpha_meta (GstBuffer * buffer,
GstBuffer * alpha_buffer)
{
GstVideoCodecAlphaMeta *meta;
g_return_val_if_fail (buffer != NULL, NULL);
g_return_val_if_fail (alpha_buffer != NULL, NULL);
meta =
(GstVideoCodecAlphaMeta *) gst_buffer_add_meta (buffer,
GST_VIDEO_CODEC_ALPHA_META_INFO, alpha_buffer);
return meta;
}