New version of loading video files

Now, the frame_selector is actually used inside the preprocessor.Wrapper class.

bob/bio/video/database/database.py

@@ -3,12 +3,8 @@
 # Tiago de Freitas Pereira <tiago.pereira@idiap.ch>
 # Wed 20 July 14:43:22 CEST 2016
 
-"""
-  Verification API for bob.db.voxforge
-"""
-
 from bob.bio.base.database.file import BioFile
-from bob.bio.video.utils.FrameSelector import FrameSelector
+from ..utils import FrameSelector
 
 
 class VideoBioFile(BioFile):
@@ -19,8 +15,5 @@ class VideoBioFile(BioFile):
         """
         super(VideoBioFile, self).__init__(client_id=client_id, path=path, file_id=file_id)
 
-    def load(self, directory=None, extension='.avi'):
-        return FrameSelector()(self.make_path(directory, extension))
-
-
-
+    def load(self, directory=None, extension='.avi', frame_selector = FrameSelector()):
+        return frame_selector(self.make_path(directory, extension))

[Amir MOHAMMADI]

frame_selector = FrameSelector() This is a very common python bug. You have to write it like this:

    def load(self, directory=None, extension='.avi', frame_selector=None):
        if frame_selector is None:
            frame_selector = FrameSelector()

[Manuel Günther]

What is wrong in my implementation? When I do not specify the frame_selector, I want to have the default one. I know that this uses the same frame_selector object by default, but I don't see why this should not work...

[Amir MOHAMMADI]

http://effbot.org/zone/default-values.htm

[Manuel Günther]

I know this effect, and I am making use of that here. In the FrameSelector (https://gitlab.idiap.ch/bob/bob.bio.video/blob/master/bob/bio/video/utils/FrameSelector.py) class there is no internal variables other than the ones specified in the constructor. Hence, calling one of its functions does not modify the object. Therefore, it is safe to use the same object each time, there is no need to create a new object, i.e., when None is passed.