Make missing annotations None instead of empty dict

bob/bio/video/annotator/FailSafeVideo.py

@@ -41,7 +41,7 @@ class FailSafeVideo(Base):
     if isinstance(frames, utils.FrameContainer):
       frames = frames.as_array()
     annotations = OrderedDict()
-    current = {}
+    current = None
     age = 0
     for i, frame in enumerate(frames):
       for annotator in self.annotators:
@@ -54,7 +54,7 @@ class FailSafeVideo(Base):
           age += 1
           break
         else:  # no detections and age is larger than maximum allowed
-          current = {}
+          current = None
 
         if current is not annot:
           logger.debug("Annotator `%s' failed.", annotator)

bob/bio/video/annotator/__init__.py

@@ -28,7 +28,7 @@ def normalize_annotations(annotations, validator, max_age=-1):
         The corrected annotations of the frame.
     """
     # the annotations for the current frame
-    current = {}
+    current = None
     age = 0
 
     for k, annot in annotations.items():
@@ -38,7 +38,7 @@ def normalize_annotations(annotations, validator, max_age=-1):
         elif max_age < 0 or age < max_age:
             age += 1
         else:  # no detections and age is larger than maximum allowed
-            current = {}
+            current = None
 
         yield k, current