I have created a deep learning model to classify activities, it classifes known (labelled) activites well, however when i attempt to classify new data the trained model has not seen beofre i want it to classify it as 'unknow'. Is there a method that can do this? The problem i have is that the number of possible classes is infinate and i am oinly intreasted in the main classes.
I have tried using the confidence scores to say, if confidence score mean is <= xx for all know activites then classify as "unknow", however with little sucess. Are there any other methods i could try?