first of all, I want to say that the program is amazing. I have been looking for a long time for an open source program to analyse sport clips.   

So now my question: I am a swim coach and for me it is necessary to define a scale (e.g. Pixel to cm) to measure length and to calculate the velocity. I know it is not so easy because of the perspective, but if I have my reference scale more or less in the same "depth layer" so it is nearly correct.

Is there an option to define a reference and to measure length etc.? Otherwise would it be possible to add this as a new feature? I guess it is not so complicated to create an Interface to define the reference scale, right?

Thanks for this great program.
Daniel

PS. I hope, my English isn't too bad and you can understand me