alphadecodebin: Add wrappers to decode VP8/VP9 alpha

This includes base class with wrappers bin that will create a static
pipeline capable of handling the VP8/VP9 alpha channel decoding
using two instances of vp8/vp9dec element each.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gst-plugins-bad/-/merge_requests/2199>

gst/codecalpha/gstalphadecodebin.c

@@ -0,0 +1,219 @@
+/* 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 <gst/pbutils/pbutils.h>
+
+#include "gstalphadecodebin.h"
+
+GST_DEBUG_CATEGORY_STATIC (alphadecodebin_debug);
+#define GST_CAT_DEFAULT (alphadecodebin_debug)
+
+typedef struct
+{
+  GstBin parent;
+
+  gboolean constructed;
+  const gchar *missing_element;
+} GstAlphaDecodeBinPrivate;
+
+#define gst_alpha_decode_bin_parent_class parent_class
+G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GstAlphaDecodeBin, gst_alpha_decode_bin,
+    GST_TYPE_BIN,
+    G_ADD_PRIVATE (GstAlphaDecodeBin);
+    GST_DEBUG_CATEGORY_INIT (alphadecodebin_debug, "alphadecodebin", 0,
+        "alphadecodebin"));
+
+static GstStaticPadTemplate gst_alpha_decode_bin_src_template =
+GST_STATIC_PAD_TEMPLATE ("src",
+    GST_PAD_SRC,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("ANY")
+    );
+
+static gboolean
+gst_alpha_decode_bin_open (GstAlphaDecodeBin * self)
+{
+  GstAlphaDecodeBinPrivate *priv =
+      gst_alpha_decode_bin_get_instance_private (self);
+
+  if (priv->missing_element) {
+    gst_element_post_message (GST_ELEMENT (self),
+        gst_missing_element_message_new (GST_ELEMENT (self),
+            priv->missing_element));
+  } else if (!priv->constructed) {
+    GST_ELEMENT_ERROR (self, CORE, FAILED,
+        ("Failed to construct alpha decoder pipeline."), (NULL));
+  }
+
+  return priv->constructed;
+}
+
+static GstStateChangeReturn
+gst_alpha_decode_bin_change_state (GstElement * element,
+    GstStateChange transition)
+{
+  GstAlphaDecodeBin *self = GST_ALPHA_DECODE_BIN (element);
+
+  switch (transition) {
+    case GST_STATE_CHANGE_NULL_TO_READY:
+      if (!gst_alpha_decode_bin_open (self))
+        return GST_STATE_CHANGE_FAILURE;
+      break;
+    default:
+      break;
+  }
+
+  return GST_ELEMENT_CLASS (parent_class)->change_state (element, transition);
+}
+
+static void
+gst_alpha_decode_bin_constructed (GObject * obj)
+{
+  GstAlphaDecodeBin *self = GST_ALPHA_DECODE_BIN (obj);
+  GstAlphaDecodeBinPrivate *priv =
+      gst_alpha_decode_bin_get_instance_private (self);
+  GstAlphaDecodeBinClass *klass = GST_ALPHA_DECODE_BIN_GET_CLASS (self);
+  GstPad *src_gpad, *sink_gpad;
+  GstPad *src_pad = NULL, *sink_pad = NULL;
+  GstElement *alphademux = NULL;
+  GstElement *multiqueue = NULL;
+  GstElement *decoder = NULL;
+  GstElement *alpha_decoder = NULL;
+  GstElement *alphacombine = NULL;
+
+  /* setup ghost pads */
+  sink_gpad = gst_ghost_pad_new_no_target_from_template ("sink",
+      gst_element_class_get_pad_template (GST_ELEMENT_CLASS (klass), "sink"));
+  gst_element_add_pad (GST_ELEMENT (self), sink_gpad);
+
+  src_gpad = gst_ghost_pad_new_no_target_from_template ("src",
+      gst_element_class_get_pad_template (GST_ELEMENT_CLASS (klass), "src"));
+  gst_element_add_pad (GST_ELEMENT (self), src_gpad);
+
+  /* create elements */
+  alphademux = gst_element_factory_make ("codecalphademux", NULL);
+  if (!alphademux) {
+    priv->missing_element = "codecalphademux";
+    goto cleanup;
+  }
+
+  multiqueue = gst_element_factory_make ("multiqueue", NULL);
+  if (!multiqueue) {
+    priv->missing_element = "multiqueue";
+    goto cleanup;
+  }
+
+  decoder = gst_element_factory_make (klass->decoder_name, NULL);
+  if (!decoder) {
+    priv->missing_element = klass->decoder_name;
+    goto cleanup;
+  }
+
+  alpha_decoder = gst_element_factory_make (klass->decoder_name, NULL);
+  if (!alpha_decoder) {
+    priv->missing_element = klass->decoder_name;
+    goto cleanup;
+  }
+
+  alphacombine = gst_element_factory_make ("alphacombine", NULL);
+  if (!alphacombine) {
+    priv->missing_element = "alphacombine";
+    goto cleanup;
+  }
+
+  gst_bin_add_many (GST_BIN (self), alphademux, multiqueue, decoder,
+      alpha_decoder, alphacombine, NULL);
+
+  /* link elements */
+  sink_pad = gst_element_get_static_pad (alphademux, "sink");
+  gst_ghost_pad_set_target (GST_GHOST_PAD (sink_gpad), sink_pad);
+  gst_clear_object (&sink_pad);
+
+  sink_pad = gst_element_request_pad_simple (multiqueue, "sink_0");
+  src_pad = gst_element_get_static_pad (multiqueue, "src_0");
+  g_object_set (sink_pad, "group_id", 0, NULL);
+  g_object_set (src_pad, "group_id", 0, NULL);
+  gst_clear_object (&sink_pad);
+  gst_clear_object (&src_pad);
+  gst_element_link_pads (alphademux, "src", multiqueue, "sink_0");
+  gst_element_link_pads (multiqueue, "src_0", decoder, "sink");
+  gst_element_link_pads (decoder, "src", alphacombine, "sink");
+
+  sink_pad = gst_element_request_pad_simple (multiqueue, "sink_1");
+  src_pad = gst_element_get_static_pad (multiqueue, "src_1");
+  g_object_set (sink_pad, "group_id", 1, NULL);
+  g_object_set (src_pad, "group_id", 1, NULL);
+  gst_clear_object (&sink_pad);
+  gst_clear_object (&src_pad);
+  gst_element_link_pads (alphademux, "alpha", multiqueue, "sink_1");
+  gst_element_link_pads (multiqueue, "src_1", alpha_decoder, "sink");
+  gst_element_link_pads (alpha_decoder, "src", alphacombine, "alpha");
+
+  src_pad = gst_element_get_static_pad (alphacombine, "src");
+  gst_ghost_pad_set_target (GST_GHOST_PAD (src_gpad), src_pad);
+  gst_object_unref (src_pad);
+
+  gst_element_link_pads (alphademux, "alpha", multiqueue, "sink_0");
+
+  /* configure the elements */
+  g_object_set (multiqueue, "max-size-bytes", 0, "max-size-time", 0,
+      "max-size-buffers", 1, NULL);
+
+  /* signal success, we will handle this in NULL->READY transition */
+  priv->constructed = TRUE;
+  return;
+
+cleanup:
+  gst_clear_object (&alphademux);
+  gst_clear_object (&multiqueue);
+  gst_clear_object (&decoder);
+  gst_clear_object (&alpha_decoder);
+  gst_clear_object (&alphacombine);
+
+  G_OBJECT_CLASS (parent_class)->constructed (obj);
+}
+
+static void
+gst_alpha_decode_bin_class_init (GstAlphaDecodeBinClass * klass)
+{
+  GstElementClass *element_class = (GstElementClass *) klass;
+  GObjectClass *obj_class = (GObjectClass *) klass;
+
+  /* This is needed to access the subclass class instance, otherwise we cannot
+   * read the class parameters */
+  obj_class->constructed = gst_alpha_decode_bin_constructed;
+
+  gst_element_class_add_static_pad_template (element_class,
+      &gst_alpha_decode_bin_src_template);
+  element_class->change_state =
+      GST_DEBUG_FUNCPTR (gst_alpha_decode_bin_change_state);
+
+  /* let's make the doc generator happy */
+  gst_type_mark_as_plugin_api (GST_TYPE_ALPHA_DECODE_BIN, 0);
+}
+
+static void
+gst_alpha_decode_bin_init (GstAlphaDecodeBin * self)
+{
+}

gst/codecalpha/gstalphadecodebin.h

@@ -0,0 +1,48 @@
+/* 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.
+ */
+
+#ifndef __GST_ALPHA_DECODE_BIN_H__
+#define __GST_ALPHA_DECODE_BIN_H__
+
+#include <gst/gst.h>
+
+/* When wrapping, use the original rank plus this offset. The ad-hoc rules is
+ * that hardware implementation will use PRIMARY+1 or +2 to override the
+ * software decoder, so the offset must be large enough to jump over those.
+ * This should also be small enough so that a marginal (64) or secondary
+ * wrapper does not cross the PRIMARY line.
+ */
+#define GST_ALPHA_DECODE_BIN_RANK_OFFSET 10
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_ALPHA_DECODE_BIN (gst_alpha_decode_bin_get_type())
+G_DECLARE_DERIVABLE_TYPE (GstAlphaDecodeBin,
+    gst_alpha_decode_bin, GST, ALPHA_DECODE_BIN, GstBin);
+
+struct _GstAlphaDecodeBinClass
+{
+  GstBinClass parent_class;
+
+  const gchar *decoder_name;
+};
+
+G_END_DECLS
+#endif

gst/codecalpha/gstplugin.c

@@ -26,6 +26,16 @@
 
 #include "gstcodecalphademux.h"
 #include "gstalphacombine.h"
+#include "gstvp8alphadecodebin.h"
+#include "gstvp9alphadecodebin.h"
+
+/* When wrapping, use the original rank plus this offset. The ad-hoc rules is
+ * that hardware implementation will use PRIMARY+1 or +2 to override the
+ * software decoder, so the offset must be large enough to jump over those.
+ * This should also be small enough so that a marginal (64) or secondary
+ * wrapper does not cross the PRIMARY line.
+ */
+#define RANK_OFFSET 10
 
 static gboolean
 plugin_init (GstPlugin * plugin)
@@ -34,6 +44,8 @@ plugin_init (GstPlugin * plugin)
 
   ret |= GST_ELEMENT_REGISTER (codec_alpha_demux, plugin);
   ret |= GST_ELEMENT_REGISTER (alpha_combine, plugin);
+  ret |= GST_ELEMENT_REGISTER (vp8_alpha_decode_bin, plugin);
+  ret |= GST_ELEMENT_REGISTER (vp9_alpha_decode_bin, plugin);
 
   return ret;
 }

gst/codecalpha/gstvp8alphadecodebin.c

@@ -0,0 +1,73 @@
+/* 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.
+ */
+
+/**
+ * SECTION:element-vp8alphadecodebin
+ * @title: Wrapper to decode VP8 alpha using vp8dec
+ *
+ * Use two `vp8dec` instance in order to decode VP8 alpha channel.
+ *
+ * Since: 1.20
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstvp8alphadecodebin.h"
+
+static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("video/x-vp8, codec-alpha = (boolean) true")
+    );
+
+struct _GstVp8AlphaDecodeBin
+{
+  GstAlphaDecodeBin parent;
+};
+
+#define gst_vp8_alpha_decode_bin_parent_class parent_class
+G_DEFINE_TYPE (GstVp8AlphaDecodeBin, gst_vp8_alpha_decode_bin,
+    GST_TYPE_ALPHA_DECODE_BIN);
+
+GST_ELEMENT_REGISTER_DEFINE (vp8_alpha_decode_bin, "vp8alphadecodebin",
+    GST_RANK_PRIMARY + GST_ALPHA_DECODE_BIN_RANK_OFFSET,
+    GST_TYPE_VP8_ALPHA_DECODE_BIN);
+
+static void
+gst_vp8_alpha_decode_bin_class_init (GstVp8AlphaDecodeBinClass * klass)
+{
+  GstAlphaDecodeBinClass *adbin_class = (GstAlphaDecodeBinClass *) klass;
+  GstElementClass *element_class = (GstElementClass *) klass;
+
+  adbin_class->decoder_name = "vp8dec";
+  gst_element_class_add_static_pad_template (element_class, &sink_template);
+
+  gst_element_class_set_static_metadata (element_class,
+      "VP8 Alpha Decoder", "Codec/Decoder/Video",
+      "Wrapper bin to decode VP8 with alpha stream.",
+      "Nicolas Dufresne <nicolas.dufresne@collabora.com>");
+}
+
+static void
+gst_vp8_alpha_decode_bin_init (GstVp8AlphaDecodeBin * self)
+{
+}

gst/codecalpha/gstvp8alphadecodebin.h

@@ -0,0 +1,35 @@
+/* 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.
+ */
+
+#ifndef __GST_VP8_ALPHA_DECODE_BIN_H__
+#define __GST_VP8_ALPHA_DECODE_BIN_H__
+
+#include "gstalphadecodebin.h"
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_VP8_ALPHA_DECODE_BIN (gst_vp8_alpha_decode_bin_get_type())
+G_DECLARE_FINAL_TYPE (GstVp8AlphaDecodeBin, gst_vp8_alpha_decode_bin,
+    GST, VP8_ALPHA_DECODE_BIN, GstAlphaDecodeBin);
+
+GST_ELEMENT_REGISTER_DECLARE (vp8_alpha_decode_bin);
+
+G_END_DECLS
+#endif

gst/codecalpha/gstvp9alphadecodebin.c

@@ -0,0 +1,73 @@
+/* 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.
+ */
+
+/**
+ * SECTION:element-vp9alphadecodebin
+ * @title: Wrapper to decode VP9 alpha using vp9dec
+ *
+ * Use two `vp9dec` instance in order to decode VP9 alpha channel.
+ *
+ * Since: 1.20
+ */
+
+#ifdef HAVE_CONFIG_H
+#include "config.h"
+#endif
+
+#include "gstvp9alphadecodebin.h"
+
+static GstStaticPadTemplate sink_template = GST_STATIC_PAD_TEMPLATE ("sink",
+    GST_PAD_SINK,
+    GST_PAD_ALWAYS,
+    GST_STATIC_CAPS ("video/x-vp9, codec-alpha = (boolean) true")
+    );
+
+struct _GstVp9AlphaDecodeBin
+{
+  GstAlphaDecodeBin parent;
+};
+
+#define gst_vp9_alpha_decode_bin_parent_class parent_class
+G_DEFINE_TYPE (GstVp9AlphaDecodeBin, gst_vp9_alpha_decode_bin,
+    GST_TYPE_ALPHA_DECODE_BIN);
+
+GST_ELEMENT_REGISTER_DEFINE (vp9_alpha_decode_bin, "vp9alphadecodebin",
+    GST_RANK_PRIMARY + GST_ALPHA_DECODE_BIN_RANK_OFFSET,
+    GST_TYPE_VP9_ALPHA_DECODE_BIN);
+
+static void
+gst_vp9_alpha_decode_bin_class_init (GstVp9AlphaDecodeBinClass * klass)
+{
+  GstAlphaDecodeBinClass *adbin_class = (GstAlphaDecodeBinClass *) klass;
+  GstElementClass *element_class = (GstElementClass *) klass;
+
+  adbin_class->decoder_name = "vp9dec";
+  gst_element_class_add_static_pad_template (element_class, &sink_template);
+
+  gst_element_class_set_static_metadata (element_class,
+      "VP9 Alpha Decoder", "Codec/Decoder/Video",
+      "Wrapper bin to decode VP9 with alpha stream.",
+      "Nicolas Dufresne <nicolas.dufresne@collabora.com>");
+}
+
+static void
+gst_vp9_alpha_decode_bin_init (GstVp9AlphaDecodeBin * self)
+{
+}

gst/codecalpha/gstvp9alphadecodebin.h

@@ -0,0 +1,35 @@
+/* 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.
+ */
+
+#ifndef __GST_VP9_ALPHA_DECODE_BIN_H__
+#define __GST_VP9_ALPHA_DECODE_BIN_H__
+
+#include "gstalphadecodebin.h"
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_VP9_ALPHA_DECODE_BIN (gst_vp9_alpha_decode_bin_get_type())
+G_DECLARE_FINAL_TYPE (GstVp9AlphaDecodeBin,
+    gst_vp9_alpha_decode_bin, GST, VP9_ALPHA_DECODE_BIN, GstAlphaDecodeBin);
+
+GST_ELEMENT_REGISTER_DECLARE (vp9_alpha_decode_bin);
+
+G_END_DECLS
+#endif

gst/codecalpha/meson.build

@@ -1,6 +1,9 @@
 codecalpha_sources = [
   'gstplugin.c',
   'gstalphacombine.c',
+  'gstalphadecodebin.c',
+  'gstvp8alphadecodebin.c',
+  'gstvp9alphadecodebin.c',
   'gstcodecalphademux.c',
 ]
 
@@ -8,7 +11,7 @@ gstcodecalpha = library('gstcodecalpha',
   codecalpha_sources,
   c_args : gst_plugins_bad_args,
   include_directories : [configinc],
-  dependencies : [gstvideo_dep],
+  dependencies : [gstvideo_dep, gstpbutils_dep],
   install : true,
   install_dir : plugins_install_dir,
 )