Physiological Signal
Definition
A biological process visible in video, such as eye blinking, rPPG (remote photoplethysmography), and head micro-motion from the cardiac cycle, that deepfake generators typically fail to replicate accurately.
- Examples
- Eye blinking, rPPG, cardiac-cycle micro-motion
- rPPG meaning
- Remote photoplethysmography
- Weakness exploited
- Deepfake generators typically fail to replicate it
- Field
- Deepfake and video forgery detection
Common questions
How does remote photoplethysmography help detect a deepfake video?+
rPPG measures subtle colour changes in skin caused by blood flow with each heartbeat. A real face on video shows a consistent, physiologically plausible pulse signal, while a synthetic face generated frame by frame often lacks this signal or produces one that is inconsistent or physiologically implausible.
Why do physiological signals remain harder for deepfake generators to fake than facial appearance?+
Generators are typically trained to reproduce visible appearance and motion, not the underlying biological processes like blood flow or the natural rhythm of blinking, so these signals were not directly optimised for during training and tend to look subtly wrong or absent even when the visual likeness is convincing.
Related terms
- CLIP-Based Detection
- Detection approach using OpenAI CLIP or similar vision-language foundation models as a feature extractor. The broad pre-training enables generalisation to generation methods...
- CNN Residual Detector
- A convolutional neural network trained on the high-frequency residual image, the difference between the original and a de-noised version, to classify whether...
- Detection Generalisation
- The capacity of a trained detector to correctly identify deepfakes produced by generators not seen during training. Low generalisation is the central...
- FaceForensics++
- A video dataset released by Rossler et al. (2019) containing 1000+ YouTube videos manipulated by four methods: DeepFakes, Face2Face, FaceSwap, and NeuralTextures....
- Frequency-Domain Analysis
- Detection approach that transforms image patches into the frequency domain (DCT or FFT) to expose periodic artifacts introduced by upsampling layers in...
- Frequency-Domain Artefact
- A periodic or statistical anomaly in the Fourier spectrum of an image or audio signal introduced by the generation pipeline's upsampling, filter,...
- Generalisation Gap
- The drop in detection accuracy when a classifier trained on one generation method is applied to a different method. Caused by learning...
- Noiseprint
- A CNN-based camera-model fingerprint extractor by Cozzolino and Verdoliva. Applied to deepfakes, it reveals inconsistency between the camera fingerprint in the genuine...
- Remote Photoplethysmography (rPPG)
- A technique that detects the pulse-driven skin-colour variation in a face video without contact sensors. In real video, this signal is present...
- rPPG
- Remote photoplethysmography. A technique for measuring heart rate from subtle periodic colour changes in facial skin caused by blood-volume pulses. Authentic video...
- XceptionNet
- A depthwise-separable convolutional architecture proposed by Rossler et al. as the baseline binary classifier in FaceForensics++. Trained to distinguish real from manipulated...