plugins: add gst_vaapi_copy_va_buffer()

This helper function aims to copy buffers with VA memory to dumb
buffers, when GstVideoMeta is not available dowstream.

https://bugzilla.gnome.org/show_bug.cgi?id=785054

gst/vaapi/gstvaapipluginbase.c

@@ -34,6 +34,7 @@
 # include <gst/gl/gl.h>
 #endif
 
+GST_DEBUG_CATEGORY_STATIC (CAT_PERFORMANCE);
 /* Default debug category is from the subclass */
 #define GST_CAT_DEFAULT (plugin->debug_category)
 
@@ -1374,3 +1375,68 @@ gst_vaapi_plugin_base_set_srcpad_can_dmabuf (GstVaapiPluginBase * plugin,
           "EGL_EXT_image_dma_buf_import"));
 #endif
 }
+
+static void
+_init_performance_debug (void)
+{
+#ifndef GST_DISABLE_GST_DEBUG
+  static volatile gsize _init = 0;
+
+  if (g_once_init_enter (&_init)) {
+    GST_DEBUG_CATEGORY_GET (CAT_PERFORMANCE, "GST_PERFORMANCE");
+    g_once_init_leave (&_init, 1);
+  }
+#endif
+}
+
+/**
+ * gst_vaapi_plugin_copy_va_buffer:
+ * @plugin: a #GstVaapiPluginBase
+ * @inbuf: a #GstBuffer with VA memory type
+ * @outbuf: a #GstBuffer with system allocated memory
+ *
+ * Copy @inbuf to @outbuf. This if required when downstream doesn't
+ * support GstVideoMeta, and since VA memory may have custom strides a
+ * frame copy is required.
+ *
+ * Returns: %FALSE if the copy failed, otherwise %TRUE. Also returns
+ *          %TRUE if it is not required to do the copy
+ **/
+gboolean
+gst_vaapi_plugin_copy_va_buffer (GstVaapiPluginBase * plugin,
+    GstBuffer * inbuf, GstBuffer * outbuf)
+{
+  GstVideoMeta *vmeta;
+  GstVideoFrame src_frame, dst_frame;
+  gboolean success;
+
+  if (!plugin->copy_output_frame)
+    return TRUE;
+
+  /* inbuf shall have video meta */
+  vmeta = gst_buffer_get_video_meta (inbuf);
+  if (!vmeta)
+    return FALSE;
+
+  _init_performance_debug ();
+  GST_CAT_INFO (CAT_PERFORMANCE, "copying VA buffer to system memory buffer");
+
+  if (!gst_video_frame_map (&src_frame, &plugin->srcpad_info, inbuf,
+          GST_MAP_READ))
+    return FALSE;
+  if (!gst_video_frame_map (&dst_frame, &plugin->srcpad_info, outbuf,
+          GST_MAP_WRITE)) {
+    gst_video_frame_unmap (&src_frame);
+    return FALSE;
+  }
+  success = gst_video_frame_copy (&dst_frame, &src_frame);
+  gst_video_frame_unmap (&dst_frame);
+  gst_video_frame_unmap (&src_frame);
+
+  if (success) {
+    gst_buffer_copy_into (outbuf, inbuf, GST_BUFFER_COPY_TIMESTAMPS
+        | GST_BUFFER_COPY_FLAGS, 0, -1);
+  }
+
+  return success;
+}

gst/vaapi/gstvaapipluginbase.h

@@ -258,6 +258,12 @@ void
 gst_vaapi_plugin_base_set_srcpad_can_dmabuf (GstVaapiPluginBase * plugin,
     GstObject * object);
 
+G_GNUC_INTERNAL
+gboolean
+gst_vaapi_plugin_copy_va_buffer (GstVaapiPluginBase * plugin,
+    GstBuffer * inbuf, GstBuffer * outbuf);
+
+
 G_END_DECLS
 
 #endif /* GST_VAAPI_PLUGIN_BASE_H */