What are some good approaches that I can use to count the no. of people in a crowd. Tracking each person individually is obviously not an option. Any good approaches or some references to research papers would be very helpful.
Here a convolutional neural network (cNN) based approach is presented: Image Crowd Counting Using Convolutional Neural Network and Markov Random Field
This blog post has more of a tutorial character and also present an approach based on CNNs Counting Crowds and Lines