Improving Video Deepfake Detection: A DCT-Based Approach with Patch-Level Analysis

The term deepfake refers to all those multimedia contents that were synthetically altered or created from scratch through the use of generative models. This phenomenon has become widespread due to the use of increasingly accurate and efficient architectures capable of rendering manipulated content indistinguishable from real content. In order to fight the illicit use of this powerful technology, it has become necessary to develop algorithms able to distinguish synthetic content from real ones. In this study, a new algorithm for the detection of deepfakes in digital videos is presented, focusing on the main goal of creating a fast and explainable method from a forensic perspective. To achieve this goal, the I-frames were extracted in order to provide faster computation and analysis than approaches described in literature. In addition, to identify the most discriminating regions within individual video frames, the entire frame, background, face, eyes, nose, mouth, and face frame were analyzed separately. From the Discrete Cosine Transform (DCT), the Beta components were extracted from the AC coefficients and used as input to standard classifiers (e.g., k-NN, SVM, and others) in order to identify those frequencies most discriminative for solving the task in question. Experimental results obtained on the Faceforensics++ and Celeb-DF (v2) datasets show that the eye and mouth regions are those most discriminative and able to determine the nature of the video with greater reliability than the analysis of the whole frame. The method proposed in this study is analytical, fast and does not require much computational power.