Fix: correctly handle buffering of filter computations (not relying on parent stream buffered data)

bob/io/stream/stream.py

@@ -249,7 +249,8 @@ def stream_filter(name):
 class StreamFilter(Stream):
     def __init__(self, name, parent):
         super().__init__(name=name, parent=parent)
-        pass
+        self.__loaded = None
+        self.__data = None
 
     def get_frame_indices(self, index):
         return super().get_frame_indices(index)
@@ -264,15 +265,13 @@ class StreamFilter(Stream):
     # load one or several frames
     def load(self, index=None):
         indices = self.get_frame_indices(index)
-        # return buffered data OR load from file OR process data
-        if self._Stream__loaded == indices and self._Stream__data is not None:
-            # print('loaded', self.name)
+        # if data is buffered, do not do processing again !
+        if self.__loaded == indices and self.__data is not None:
             pass
         else:
             self.__data = self.process(self.parent.load(indices), indices)
+            self.__loaded = indices
 
-        # buffer and return data
-        self.__loaded = indices
         return self.__data
 
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