Tools suitable for semi-automatic video labeling? So far I have been using labelme to label objects in videos I use for training, but it is quite time consuming. 

Are there good tools to help with that? 

I was thinking about a tool where I label some frames, and the tool would then match the labelled areas in the next frames. Note that a simple interpolation would not be enough.
You could use some tracking lib. Adrian Rosebrock gives nice overview on his blog.