Detection of Video Double Encoding with GOP Size Estimation

Video forensics is an emerging discipline that aims at inferring information about the processing history undergone by a digital video in a blind fashion. In this paper, the authors introduce a new forensic footprint and, based on it, propose a method for detecting whether a video has been encoded twice; if this is the case, they also estimate the size of the Group Of Pictures (GOP) employed during the first encoding. As shown in the experiments, the footprint proves to be very robust even in realistic settings (i.e., when encoding is carried out using typical compression rates), that are rarely addressed by existing techniques.