va: Add codec alpha decode bin base class

A VA-API decoder bin base class for codecs with alpha channel support.

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8180>

subprojects/gst-plugins-bad/sys/va/gstvacodecalphadecodebin.c

@@ -0,0 +1,263 @@
+/* GStreamer
+ * Copyright (C) <2021> Collabora Ltd.
+ *   Author: Daniel Almeida <daniel.almeida@collabora.com>
+ * Copyright (C) <2024> Harmonic Inc.
+ *   Author: Cheung Yik Pang <pang.cheung@harmonicinc.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 "gstvacodecalphadecodebin.h"
+#include "gstvapluginutils.h"
+
+GST_DEBUG_CATEGORY_STATIC (va_codecalphadecodebin_debug);
+#define GST_CAT_DEFAULT (va_codecalphadecodebin_debug)
+
+typedef struct
+{
+  GstBin parent;
+
+  gboolean constructed;
+  const gchar *missing_element;
+} GstVaCodecAlphaDecodeBinPrivate;
+
+#define gst_va_codec_alpha_decode_bin_parent_class parent_class
+G_DEFINE_ABSTRACT_TYPE_WITH_CODE (GstVaCodecAlphaDecodeBin,
+    gst_va_codec_alpha_decode_bin, GST_TYPE_BIN,
+    G_ADD_PRIVATE (GstVaCodecAlphaDecodeBin);
+    GST_DEBUG_CATEGORY_INIT (va_codecalphadecodebin_debug,
+        "vacodecs-alphadecodebin", 0, "VA stateless alpha decode bin"));
+
+
+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_va_codec_alpha_decode_bin_open (GstVaCodecAlphaDecodeBin * self)
+{
+  GstVaCodecAlphaDecodeBinPrivate *priv =
+      gst_va_codec_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_va_codec_alpha_decode_bin_change_state (GstElement * element,
+    GstStateChange transition)
+{
+  GstVaCodecAlphaDecodeBin *self = GST_VA_CODEC_ALPHA_DECODE_BIN (element);
+
+  switch (transition) {
+    case GST_STATE_CHANGE_NULL_TO_READY:
+      if (!gst_va_codec_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_va_codec_alpha_decode_bin_constructed (GObject * obj)
+{
+  GstVaCodecAlphaDecodeBin *self = GST_VA_CODEC_ALPHA_DECODE_BIN (obj);
+  GstVaCodecAlphaDecodeBinPrivate *priv =
+      gst_va_codec_alpha_decode_bin_get_instance_private (self);
+  GstVaCodecAlphaDecodeBinClass *klass =
+      GST_VA_CODEC_ALPHA_DECODE_BIN_GET_CLASS (self);
+  GstPad *src_gpad, *sink_gpad;
+  GstPad *src_pad = NULL, *sink_pad = NULL;
+  GstElement *alphademux = NULL;
+  GstElement *queue = NULL;
+  GstElement *alpha_queue = 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;
+  }
+
+  queue = gst_element_factory_make ("queue", NULL);
+  alpha_queue = gst_element_factory_make ("queue", NULL);
+  if (!queue || !alpha_queue) {
+    priv->missing_element = "queue";
+    goto cleanup;
+  }
+
+  decoder = gst_element_factory_make (klass->decoder_name, "maindec");
+  if (!decoder) {
+    priv->missing_element = klass->decoder_name;
+    goto cleanup;
+  }
+
+  alpha_decoder = gst_element_factory_make (klass->decoder_name, "alphadec");
+  if (!alpha_decoder) {
+    priv->missing_element = klass->decoder_name;
+    goto cleanup;
+  }
+
+  /* We disable QoS on decoders because we need to maintain frame pairing in
+   * order for alphacombine to work. */
+  g_object_set (decoder, "qos", FALSE, NULL);
+  g_object_set (alpha_decoder, "qos", FALSE, NULL);
+
+  alphacombine = gst_element_factory_make ("alphacombine", NULL);
+  if (!alphacombine) {
+    priv->missing_element = "alphacombine";
+    goto cleanup;
+  }
+
+  gst_bin_add_many (GST_BIN (self), alphademux, queue, alpha_queue, 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);
+
+  gst_element_link_pads (alphademux, "src", queue, "sink");
+  gst_element_link_pads (queue, "src", decoder, "sink");
+  gst_element_link_pads (decoder, "src", alphacombine, "sink");
+
+  gst_element_link_pads (alphademux, "alpha", alpha_queue, "sink");
+  gst_element_link_pads (alpha_queue, "src", 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);
+
+  g_object_set (queue, "max-size-bytes", 0, "max-size-time",
+      G_GUINT64_CONSTANT (0), "max-size-buffers", 1, NULL);
+  g_object_set (alpha_queue, "max-size-bytes", 0, "max-size-time",
+      G_GUINT64_CONSTANT (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 (&queue);
+  gst_clear_object (&alpha_queue);
+  gst_clear_object (&decoder);
+  gst_clear_object (&alpha_decoder);
+  gst_clear_object (&alphacombine);
+
+  G_OBJECT_CLASS (parent_class)->constructed (obj);
+}
+
+static void
+gst_va_codec_alpha_decode_bin_class_init (GstVaCodecAlphaDecodeBinClass * 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_va_codec_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_va_codec_alpha_decode_bin_change_state);
+
+  /* let's make the doc generator happy */
+  gst_type_mark_as_plugin_api (GST_TYPE_VA_CODEC_ALPHA_DECODE_BIN, 0);
+}
+
+static void
+gst_va_codec_alpha_decode_bin_init (GstVaCodecAlphaDecodeBin * self)
+{
+}
+
+gboolean
+gst_va_codec_alpha_decode_bin_register (GstPlugin * plugin,
+    GClassInitFunc class_init,
+    gconstpointer class_data,
+    const gchar * type_name_default,
+    const gchar * type_name_templ,
+    const gchar * feature_name_default,
+    const gchar * feature_name_templ, GstVaDevice * device, guint rank)
+{
+  GTypeQuery type_query;
+  GTypeInfo type_info = { 0, };
+  GType subtype;
+  gchar *type_name, *feature_name, *description;
+  gboolean ret;
+
+  g_return_val_if_fail (GST_IS_PLUGIN (plugin), FALSE);
+  g_return_val_if_fail (GST_IS_VA_DEVICE (device), FALSE);
+
+  description = type_name = feature_name = NULL;
+
+  g_type_query (GST_TYPE_VA_CODEC_ALPHA_DECODE_BIN, &type_query);
+  memset (&type_info, 0, sizeof (type_info));
+  type_info.class_size = type_query.class_size;
+  type_info.instance_size = type_query.instance_size;
+  type_info.class_init = class_init;
+  type_info.class_data = class_data;
+
+  gst_va_create_feature_name (device, type_name_default, type_name_templ,
+      &type_name, feature_name_default, feature_name_templ, &feature_name,
+      &description, &rank);
+
+  subtype = g_type_register_static (GST_TYPE_VA_CODEC_ALPHA_DECODE_BIN,
+      type_name, &type_info, 0);
+
+  ret = gst_element_register (plugin, feature_name,
+      rank + GST_VA_CODEC_ALPHA_DECODE_BIN_RANK_OFFSET, subtype);
+
+  g_free (type_name);
+  g_free (feature_name);
+  g_free (description);
+
+  return ret;
+}

subprojects/gst-plugins-bad/sys/va/gstvacodecalphadecodebin.h

@@ -0,0 +1,60 @@
+/* GStreamer
+ * Copyright (C) <2021> Collabora Ltd.
+ *   Author: Daniel Almeida <daniel.almeida@collabora.com>
+ * Copyright (C) <2024> Harmonic Inc.
+ *   Author: Cheung Yik Pang <pang.cheung@harmonicinc.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_VA_CODEC_ALPHA_DECODE_BIN_H__
+#define __GST_VA_CODEC_ALPHA_DECODE_BIN_H__
+
+#include <gst/gst.h>
+#include <gstvadevice.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_VA_CODEC_ALPHA_DECODE_BIN_RANK_OFFSET 10
+
+G_BEGIN_DECLS
+
+#define GST_TYPE_VA_CODEC_ALPHA_DECODE_BIN (gst_va_codec_alpha_decode_bin_get_type())
+G_DECLARE_DERIVABLE_TYPE (GstVaCodecAlphaDecodeBin,
+    gst_va_codec_alpha_decode_bin, GST, VA_CODEC_ALPHA_DECODE_BIN, GstBin);
+
+struct _GstVaCodecAlphaDecodeBinClass
+{
+  GstBinClass parent_class;
+  gchar *decoder_name;
+};
+
+gboolean gst_va_codec_alpha_decode_bin_register (GstPlugin * plugin,
+                                                 GClassInitFunc class_init,
+                                                 gconstpointer class_data,
+                                                 const gchar * type_name_default,
+                                                 const gchar * type_name_templ,
+                                                 const gchar * feature_name_default,
+                                                 const gchar * feature_name_templ,
+                                                 GstVaDevice * device,
+                                                 guint rank);
+
+G_END_DECLS
+#endif /* __GST_VA_CODEC_ALPHA_DECODE_BIN_H__ */

subprojects/gst-plugins-bad/sys/va/meson.build

@@ -7,6 +7,7 @@ va_sources = [
   'gstvabaseenc.c',
   'gstvabasetransform.c',
   'gstvacaps.c',
+  'gstvacodecalphadecodebin.c',
   'gstvacompositor.c',
   'gstvadecoder.c',
   'gstvadeinterlace.c',
@@ -137,7 +138,7 @@ gstva = library('gstva',
   c_args : gst_plugins_bad_args + extra_args,
   cpp_args : gst_plugins_bad_args + extra_args,
   include_directories : [configinc, libsinc],
-  dependencies : [gstcodecs_dep, gstva_dep, libgudev_dep, libm] + extra_dep,
+  dependencies : [gstcodecs_dep, gstva_dep, libgudev_dep, libm, gstpbutils_dep] + extra_dep,
   override_options : c_std_arg,
   install : true,
   install_dir : plugins_install_dir,