gl: add a sync meta for synchronizing across GL contexts

A context can create a GLsync object that can be waited on in order
to ensure that GL resources created in one context are able to be
used in another shared context without any chance of reading invalid
data.

This meta would be placed on buffers that are known to cross from
one context to another.  The receiving element would then wait
on the sync object to ensure that the data to be used is complete.

diff --git a/ext/gl/gstglmixer.c b/ext/gl/gstglmixer.c
index bd63c75a1fbb463b87ba85c3bdfb45624bade646..e245bc29fefd2b88637117aa585de23f0b4ac186 100644 (file)
--- a/ext/gl/gstglmixer.c
+++ b/ext/gl/gstglmixer.c
@@ -223,6 +223,8 @@ gst_gl_mixer_propose_allocation (GstGLMixer * mix,
 
   /* we also support various metadata */
   gst_query_add_allocation_meta (query, GST_VIDEO_META_API_TYPE, 0);
+  if (mix->context->gl_vtable->FenceSync)
+    gst_query_add_allocation_meta (query, GST_GL_SYNC_META_API_TYPE, 0);
 
   gl_apis = gst_gl_api_to_string (gst_gl_context_get_gl_api (mix->context));
   platform =
@@ -778,6 +780,7 @@ gst_gl_mixer_decide_allocation (GstGLMixer * mix, GstQuery * query)
   guint out_width, out_height;
   GstGLContext *other_context = NULL;
   GstVideoAggregator *vagg = GST_VIDEO_AGGREGATOR (mix);
+  gboolean same_downstream_gl_context = FALSE;
 
   if (!gst_gl_ensure_element_data (mix, &mix->display, &mix->other_context))
     return FALSE;
@@ -799,6 +802,7 @@ gst_gl_mixer_decide_allocation (GstGLMixer * mix, GstQuery * query)
         mix->context = context;
         if (old)
           gst_object_unref (old);
+        same_downstream_gl_context = TRUE;
       } else if (gst_structure_get (upload_meta_params, "gst.gl.context.handle",
               G_TYPE_POINTER, &handle, "gst.gl.context.type", G_TYPE_STRING,
               &type, "gst.gl.context.apis", G_TYPE_STRING, &apis, NULL)
@@ -882,13 +886,23 @@ gst_gl_mixer_decide_allocation (GstGLMixer * mix, GstQuery * query)
     update_pool = FALSE;
   }
 
-  if (!pool)
+  if (!pool || (!same_downstream_gl_context
+          && gst_query_find_allocation_meta (query, GST_GL_SYNC_META_API_TYPE,
+              NULL)
+          && !gst_buffer_pool_has_option (pool,
+              GST_BUFFER_POOL_OPTION_GL_SYNC_META))) {
+    /* can't use this pool */
+    if (pool)
+      gst_object_unref (pool);
     pool = gst_gl_buffer_pool_new (mix->context);
-
+  }
   config = gst_buffer_pool_get_config (pool);
-  gst_buffer_pool_config_set_params (config, caps, size, min, max);
 
+  gst_buffer_pool_config_set_params (config, caps, size, min, max);
   gst_buffer_pool_config_add_option (config, GST_BUFFER_POOL_OPTION_VIDEO_META);
+  if (gst_query_find_allocation_meta (query, GST_GL_SYNC_META_API_TYPE, NULL))
+    gst_buffer_pool_config_add_option (config,
+        GST_BUFFER_POOL_OPTION_GL_SYNC_META);
   gst_buffer_pool_config_add_option (config,
       GST_BUFFER_POOL_OPTION_VIDEO_GL_TEXTURE_UPLOAD_META);
 
@@ -1075,6 +1089,7 @@ gst_gl_mixer_process_textures (GstGLMixer * mix, GstBuffer * outbuf)
       GstCapsFeatures *gl_features;
       GstVideoInfo gl_info;
       GstVideoFrame gl_frame;
+      GstGLSyncMeta *sync_meta;
 
       gst_video_info_set_format (&gl_info,
           GST_VIDEO_FORMAT_RGBA,
@@ -1096,6 +1111,10 @@ gst_gl_mixer_process_textures (GstGLMixer * mix, GstBuffer * outbuf)
         gst_caps_unref (in_caps);
       }
 
+      sync_meta = gst_buffer_get_gl_sync_meta (vaggpad->buffer);
+      if (sync_meta)
+        gst_gl_sync_meta_wait (sync_meta);
+
       if (!gst_gl_upload_perform_with_buffer (pad->upload,
               vaggpad->buffer, &gl_buf)) {
         ++array_index;
@@ -1207,12 +1226,17 @@ gst_gl_mixer_aggregate_frames (GstVideoAggregator * vagg, GstBuffer * outbuf)
   gboolean res = FALSE;
   GstGLMixer *mix = GST_GL_MIXER (vagg);
   GstGLMixerClass *mix_class = GST_GL_MIXER_GET_CLASS (vagg);
+  GstGLSyncMeta *sync_meta;
 
   if (mix_class->process_buffers)
     res = gst_gl_mixer_process_buffers (mix, outbuf);
   else if (mix_class->process_textures)
     res = gst_gl_mixer_process_textures (mix, outbuf);
 
+  sync_meta = gst_buffer_get_gl_sync_meta (outbuf);
+  if (sync_meta)
+    gst_gl_sync_meta_set_sync_point (sync_meta, mix->context);
+
   return res ? GST_FLOW_OK : GST_FLOW_ERROR;
 }