make the datasets compatible with pyrception - manually transferred the code from branch fod_generator_randomization_changes commit fce50a

com.unity.perception/Runtime/GroundTruth/DatasetCapture.cs

             return ego;
         }
 
+        public static void AddMetadata(string key, object value)
+        {
+            SimulationState.AddMetadata(key, value);
+        }
+
         /// <summary>
         /// Register a new sensor under the given ego.
         /// </summary>

com.unity.perception/Runtime/GroundTruth/PerceptionCamera.cs

                 inMatrix[2,0],inMatrix[2,1], inMatrix[2,2]);
         }
 
+        int m_CaptureCount = 0;
+
         void CaptureRgbData(Camera cam)
         {
             if (!captureRgbImages)
 #else
             CaptureCamera.Capture(cam, colorFunctor, flipY: flipY);
 #endif
+            DatasetCapture.AddMetadata("image_width", attachedCamera.pixelWidth);
+            DatasetCapture.AddMetadata("image_height", attachedCamera.pixelHeight);
+            DatasetCapture.AddMetadata("dataset_size", ++m_CaptureCount);
+
             Profiler.EndSample();
         }
 

com.unity.perception/Runtime/GroundTruth/SimulationState.cs

         Dictionary<SensorHandle, SensorData> m_Sensors = new Dictionary<SensorHandle, SensorData>();
         HashSet<EgoHandle> m_Egos = new HashSet<EgoHandle>();
         HashSet<Guid> m_Ids = new HashSet<Guid>();
+        Dictionary<string, object> m_Metadata = new Dictionary<string, object>();
         Guid m_SequenceId = Guid.NewGuid();
 
         // Always use the property SequenceTimeMs instead
             m_Ids.Add(egoHandle.Id);
         }
 
+        public void AddMetadata(string key, object value)
+        {
+            if (!m_Metadata.ContainsKey(key)) m_Metadata[key] = null;
+            m_Metadata[key] = value;
+        }
 
         public bool IsEnabled(SensorHandle sensorHandle) => m_ActiveSensors.Contains(sensorHandle);
 
                 Debug.LogError($"Simulation ended with pending metrics: {string.Join(", ", m_PendingMetrics.Select(c => $"id:{c.MetricId} step:{c.Step}"))}");
 
             WriteReferences();
+
+            // TODO write metadata here
+            WriteMetadata();
+
             Time.captureDeltaTime = 0;
             IsRunning = false;
         }

com.unity.perception/Runtime/GroundTruth/SimulationState_Json.cs

     {
         const Formatting k_Formatting = Formatting.Indented;
 
+        public void WriteMetadata()
+        {
+            var metadata = new JObject();
+            metadata["version"] = DatasetCapture.SchemaVersion;
+            metadata["per_file_size"] = k_MinPendingMetricsBeforeWrite;
+
+            foreach (var md in m_Metadata)
+            {
+                metadata[md.Key] = JToken.FromObject(md.Value);
+            }
+
+
+            //metadata["dataset_size"] = 500;
+            //metadata["per_file_size"] = 150;
+            //metadata["image_width"] = 1024;
+            //metadata["image_height"] = 768;
+            WriteJObjectToFile(metadata, "metadata.json");
+        }
+
         /// <summary>
         /// Writes sensors.json, egos.json, metric_definitions.json, and annotation_definitions.json
         /// </summary>