It is not advised to just extract some data and feeding it to the network which most people do. In practical, success and performance of a neural network depends on the Pre-processing and choosing of right features. The ANN is made for fixed feature vector length so you won't be able to use it.But you may use other classifiers such as random forest which uses a small no. of random features and creates hundreds of decision trees or can also try other solutions like using the Dynamic Time Wrapping or the interpolation.