In this paper a new and original technique to animate a crowd of human beings is presented. Following the success of data-driven animation models (such as motion capture) in the context of articulated figures control, we propose to derivate a similar type of approach for crowd motions. In our framework, the motion of the crowds are represented as a time series of velocity fields estimated from a video of a real crowd. This time series is used as an input of a simple animation model that ”advect” people along this timevarying flow. We demonstrate the power of our technique on both synthetic and real examples of crowd videos. We also introduce the notions of crowd motion editing and present possible extensions to our work.