1. Introduction
Deepfakes are manipulated images or videos that usually are an attempt to affect the image or reputation of an individual, or deepfakes are used to spread disinformation. There are times when the creation of deepfakes is for good-faith intentions, such as when MIT created a deepfake video of a speech by President Nixon alleging a failed Apollo-11 mission [
1], or when American director Jordan Peele impersonated President Obama [
2] to present a speech that seemed out of character. The altered, hyper-realistic images and videos are enough to convince people of their legitimacy. Nicolas Cage appears in a collection of videos [
3] where the actor appears in movies that he was never cast in. Deepfake creation stems from machine learning methods [
4] that have been improved upon to now using advanced deep learning techniques involving convolutional neural networks (CNN) [
5], which are deep learning models that consist of convolutional layers. These layers are able to learn patterns, or features, in images based on sub-groupings of pixels within a larger image. These feature detectors are called filters, or kernels, and are "activated" when the layer receives input from an image containing similar pixel structures. This essentially is a form of learning the contents of images, and these filters can be used with other images to detect if they contain similar pixel patterns. Since these filters are learned by the deep learning model, these models then have the ability to recreate images that would activate the filters, thus creating a deepfake [
5,
6,
7].
In recent years, there has been an increase in image and video data that only shows the periocular region instead of the entire face. This is largely due to the increase in people wearing masks because of the COVID-19 pandemic. The less-revealing faces already inhibit facial inter-personal facial recognition, but this lowered recognition also makes it easier for a deepfake to pass as realistic to a human observer. Deepfake creators that rely on face swapping and mimicry focus on prominent facial features to manipulate, such as the eyes, nose, and mouth [
5]. These features along with their expected, artifact-free observation, allow people to discern a manipulated image yet when most of the face is covered or hidden, people have less information in front of them to make that decision. Although deepfake periocular image data can be created, the process to create them still is believed to generate artifacts and inconsistencies within the created images that can be detected not only by human eyes, but also with deep learning models.
Deep learning methods have been used before to detect deepfakes, such as CNN and long short-term memory (LSTM) but there has been a lack of combining various computer vision algorithms with deep learning models. Deep learning models alone tend to perform well, that including other feature extraction methods can incur unneeded overhead without increasing performance. For example, feature extraction using scale-invariant feature transform takes a long time to extract a smaller set of features than compared to histogram of oriented gradients. Both computer vision methods can be used for object and edge detection, although the quality of the extracted features may differ significantly.
Compared to CNN, many of these computer vision methods are able to perform feature extraction at a much faster rate while using fewer resources, although classification performance is poorer. This research intends to combine feature extraction and CNN for deepfake detection, and to compare the performance of these combined models. As of this paper, there have not been significant strides made in the deep learning field for periocular-based deepfake detection. This paper will show that deep learning models using different computer vision feature extraction methods, along with combining these various models, can detect deepfakes at a significantly higher accuracy focusing only on the periocular region. Models designed around smaller smaller amounts of information are useful when only these smaller pools of data are available.
A simple example of a CNN is a model that can distinguish pictures containing cats from pictures containing dogs, or even being able to count the number of cats and dogs in a picture, along with their breed. More robust CNN are able to generate new images containing a cat or dog, to further the example. Common methods of deepfake generation involve cutting and pasting [
5], or called swapping [
8,
9,
10], the face of one person onto another. This swapping leaves artifacts in the produced image that may be noticeable to the human eye but smaller details can be detected by a machine [
9,
11]. In order to increase realism in the manipulated images, smoothing and brushing techniques are used along the bounding box of the swapped face, with key facial landmarks mapped to match the movement of the actor on the original image. The bounding box has been a focus of research [
5,
8] in detecting deepfakes since using a mask to swap a face naturally creates edges, making edge detection possible [
12]. Alterations within the swapped face are less likely to produce consistent edges since their creation is based on image augmentation [
13], as opposed to image masking.
In this paper, the dataset DeepFakeDetection [
14,
15] is used for performance evaluation. These models may then be used on other datasets from the FaceForensics++ [
14] collection to compare their results for a more general evaluation. DeepFakeDetection consists of one thousand unaltered videos, and three thousand manipulated videos based on the original videos. Since the source is video data, and frames will need to be extracted to have image data, a substantially large portion of the dataset would look similar, in that each frame of a video is only slightly different from the neighboring frame in most cases, in some cases, the neighboring frame is the exact same.
The use of CNNs for image, or image-like, learning is widely employed since the convolutional process creates smaller, stacked regions of learnable features while preserving input data. This process is performed within layers called . Between convolutions, the feature map, or activation map, will become more dense, or deeper, while the two-dimensional nature of the image data at most remains the same, while in many cases, decreases as the number of filters increase across layers. These filters activate when a learned feature is passed through them. This means that we can have many trainable filters, trained on smaller, deeper dimensions of image data to detect features that would indicate if an image is original, unaltered media, or if it has been altered and could be a deepfake.
Along with using convolutional layers, we explore some other methods that can be used to extract features from image data for deepfake classification. These methods are Scale-Invariant Feature Transform [
11,
16] (SIFT) and Histogram of Oriented Gradients [
17] (HOG). SIFT features are useful in that the features, when clustered together, are used to represent objects and biological markers within an image. These objects and markers are able to be mapped across various images, regardless of changes in scale or orientation. This presents a useful tool for object detection that can be used to detect distinguishing features in deepfake images. HOG features, when seen as in image, is more akin to edge detection and contour detection. HOG features represent changes in angle gradients, or slopes, and contrast across pixel data using Gaussian derivatives. When the image data is viewed, it is shown as a collection of angled vectors that outline the various objects in the image.
Ensemble models offer a relatively simple way to include multiple different features as input for the same process. Typically, deep neural networks have a single set of features, or a batch of similar features, for learning. These more complex models allow a single input, such as an image, to be represented by different types of features. In the case of this article, the different type of features are convolutional features, SIFT features, and HOG features. Since these features are extracted using different processes, one set of features may contain unique data that can be used effectively to distinguish original media from deepfakes. In this article, we describe how an ensemble model can be used with various feature extraction tools to accurately detect deepfakes with high performance. We will also explain the construction of the model and their performance on different datasets.