examples: Add example for nvenc extern-cuda-bufferpool property

Part-of: <https://gitlab.freedesktop.org/gstreamer/gstreamer/-/merge_requests/8516>

subprojects/gst-plugins-bad/tests/examples/cuda/meson.build

@@ -84,3 +84,9 @@ executable('cudamemorypool', 'cudamemorypool.c',
   dependencies: [gst_dep, gstvideo_dep, gstcuda_dep],
   c_args : gst_plugins_bad_args + ['-DGST_USE_UNSTABLE_API'],
   install: false)
+
+executable('nvenc-extern-pool', 'nvenc-extern-pool.c',
+  include_directories : [configinc, cuda_stubinc],
+  dependencies: [gst_dep, gstvideo_dep, gstcuda_dep],
+  c_args : gst_plugins_bad_args + ['-DGST_USE_UNSTABLE_API'],
+  install: false)

subprojects/gst-plugins-bad/tests/examples/cuda/nvenc-extern-pool.c

@@ -0,0 +1,211 @@
+/*
+ * GStreamer
+ * Copyright (C) 2025 Seungha Yang <seungha@centricular.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/gst.h>
+#include <gst/cuda/gstcuda.h>
+#include <gst/video/video.h>
+
+static GstBusSyncReply
+bus_sync_handler (GstBus * bus, GstMessage * msg, GstCudaContext * cuda_ctx)
+{
+  switch (GST_MESSAGE_TYPE (msg)) {
+    case GST_MESSAGE_NEED_CONTEXT:
+    {
+      const gchar *ctx_type;
+      gst_message_parse_context_type (msg, &ctx_type);
+      gst_println ("Got need-context %s", ctx_type);
+      if (g_strcmp0 (ctx_type, GST_CUDA_CONTEXT_TYPE) == 0) {
+        GstContext *gst_ctx = gst_context_new_cuda_context (cuda_ctx);
+        GstElement *src = GST_ELEMENT (msg->src);
+        gst_element_set_context (src, gst_ctx);
+        gst_context_unref (gst_ctx);
+      }
+      break;
+    }
+    default:
+      break;
+  }
+
+  return GST_BUS_PASS;
+}
+
+static gboolean
+bus_handler (GstBus * bus, GstMessage * msg, GMainLoop * loop)
+{
+  switch (GST_MESSAGE_TYPE (msg)) {
+    case GST_MESSAGE_EOS:
+      gst_println ("Got EOS");
+      g_main_loop_quit (loop);
+      break;
+    case GST_MESSAGE_ERROR:
+    {
+      GError *err = NULL;
+      gchar *name, *debug = NULL;
+
+      name = gst_object_get_path_string (msg->src);
+      gst_message_parse_error (msg, &err, &debug);
+
+      gst_printerrln ("ERROR: from element %s: %s", name, err->message);
+      if (debug != NULL)
+        gst_printerrln ("Additional debug info:\n%s", debug);
+
+      g_clear_error (&err);
+      g_free (debug);
+      g_free (name);
+
+      g_main_loop_quit (loop);
+      break;
+    }
+    default:
+      break;
+  }
+
+  return G_SOURCE_CONTINUE;
+}
+
+gint
+main (gint argc, gchar ** argv)
+{
+  GstCudaContext *context;
+  GstBufferPool *pool;
+  GstStructure *config;
+  GstCaps *caps;
+  GstVideoInfo info;
+  guint i;
+  GstBuffer *prealloc[16];
+  GstElement *pipeline;
+  GstElement *element;
+  GstBus *bus;
+  GMainLoop *loop;
+
+  /* Set environment to enable stream-ordered-allocation by default */
+  g_setenv ("GST_CUDA_ENABLE_STREAM_ORDERED_ALLOC", "1", TRUE);
+
+  loop = g_main_loop_new (NULL, FALSE);
+
+  gst_init (NULL, NULL);
+
+  if (!gst_cuda_load_library ()) {
+    gst_println ("Couldn't load cuda library");
+    return 0;
+  }
+
+  context = gst_cuda_context_new (0);
+  if (!context) {
+    gst_println ("Couldn't create cuda context");
+    return 0;
+  }
+
+  /* Prepares bufferpool */
+  gst_video_info_set_format (&info, GST_VIDEO_FORMAT_NV12, 1280, 720);
+  caps = gst_video_info_to_caps (&info);
+  pool = gst_cuda_buffer_pool_new (context);
+  config = gst_buffer_pool_get_config (pool);
+
+  gst_buffer_pool_config_set_params (config, caps, info.size, 0, 0);
+  gst_caps_unref (caps);
+
+  /* Because NVENC does not support stream-ordered allocated CUDA memory,
+   * we need to explicitly disable it for this buffer pool */
+  gst_buffer_pool_config_set_cuda_stream_ordered_alloc (config, FALSE);
+
+  if (!gst_buffer_pool_set_config (pool, config)) {
+    gst_printerrln ("Set config failed");
+    return 0;
+  }
+
+  if (!gst_buffer_pool_set_active (pool, TRUE)) {
+    gst_printerrln ("Set active failed");
+    return 0;
+  }
+
+  /* Preallocate buffers. Note that GstCudaBufferPool will do pre-allocation
+   * by itself even if min_buffers are set */
+  for (i = 0; i < G_N_ELEMENTS (prealloc); i++) {
+    GstBuffer *buf;
+    if (gst_buffer_pool_acquire_buffer (pool, &buf, NULL) != GST_FLOW_OK) {
+      gst_printerrln ("Couldn't allocate memory");
+      return 0;
+    }
+
+    prealloc[i] = buf;
+  }
+
+  /* Return buffers to pool */
+  for (i = 0; i < G_N_ELEMENTS (prealloc); i++)
+    gst_buffer_unref (prealloc[i]);
+
+  /* Constructs pipeline with 2 encoders. Single pool can be shared
+   * by multiple encoders if the size of pool is not smaller than encoded stream
+   * resolution */
+  pipeline = gst_parse_launch ("videotestsrc num-buffers=100 ! "
+      "video/x-raw,format=NV12,width=640,height=480 ! cudaupload ! tee name=t ! "
+      "queue ! cudascale ! "
+      "video/x-raw(memory:CUDAMemory),width=1280,height=720 ! nvh264enc name=enc0 ! "
+      "queue ! nvh264dec ! queue ! videoconvert ! autovideosink "
+      "t. ! queue ! "
+      "video/x-raw(memory:CUDAMemory),width=640,height=480 ! nvh264enc name=enc1 ! "
+      "queue ! nvh264dec ! queue ! videoconvert ! autovideosink", NULL);
+
+  if (!pipeline) {
+    gst_printerrln ("Couldn't construct pipeline");
+    return 0;
+  }
+
+  /* Pass our pool to encoders */
+  element = gst_bin_get_by_name (GST_BIN (pipeline), "enc0");
+  g_object_set (element, "extern-cuda-bufferpool", pool, NULL);
+  gst_object_unref (element);
+
+  element = gst_bin_get_by_name (GST_BIN (pipeline), "enc1");
+  g_object_set (element, "extern-cuda-bufferpool", pool, NULL);
+  gst_object_unref (element);
+
+  /* Configure bus to pass our GstCudaContext to pipeline */
+  bus = gst_element_get_bus (pipeline);
+  gst_bus_set_sync_handler (bus, (GstBusSyncHandler) bus_sync_handler,
+      context, NULL);
+
+  /* And bus watch to detect EOS or pipeline error */
+  gst_bus_add_watch (bus, (GstBusFunc) bus_handler, loop);
+
+  gst_element_set_state (pipeline, GST_STATE_PLAYING);
+  g_main_loop_run (loop);
+
+  /* Cleanup pipeline */
+  gst_element_set_state (pipeline, GST_STATE_NULL);
+  gst_bus_remove_watch (bus);
+  gst_object_unref (bus);
+  gst_object_unref (pipeline);
+
+  /* Destroy pool */
+  gst_buffer_pool_set_active (pool, FALSE);
+  gst_object_unref (pool);
+
+  gst_object_unref (context);
+
+  gst_deinit ();
+
+  return 0;
+}