Traincascade and symmetric images
I've searched, but couldn't find any reference. Has the newer "traincascade" any concern about the symmetric images? For example logos can't be mirrored, but faces yes and thus the detection could be improved. I know that about the "haartraining" that it has any, but the "traincascade"?
If you mean that mirroring your training data on over the y axis to improve your detection rate, then yes traincascade will improve, especially if your head is not 100% aligned correctly, since you will have slightly different training samples. However, do use enough samples in order to avoid overfitting by this measurement.
Yes, I meant that, but I thought, that I can solve it automatically either with traincascade or createsamples.
Nope it isn't integrated to do that automatically. Just write a small script to double your training set by flipping them all. That is what I do most of the times.