Face verification remains a challenging problem in very complex conditions with large variations such as pose, illumination, expression, and occlusions. This problem is exacerbated when we rely unrealistically on a single training data source, which is often insufficient to cover the intrinsically complex face variations. This paper proposes a principled multi-task learning approach based on Discriminative Gaussian Process Latent Variable Model, named GaussianFace, to enrich the diversity of training data. In comparison to existing methods, our model exploits additional data from multiple source-domains to improve the generalization performance of face verification in an unknown target-domain. Importantly, our model can adapt automatically to complex data distributions, and therefore can well capture complex face variations inherent in multiple sources. Extensive experiments demonstrate the effectiveness of the proposed model in learning from diverse data sources and generalize to unseen domain. Specifically, the accuracy of our algorithm achieves an impressive accuracy rate of 98.52% on the well-known and challenging Labeled Faces in the Wild (LFW) benchmark. For the first time, the human-level performance in face verification (97.53%) on LFW is surpassed.
There is an implicit belief among many psychologists and computer scientists that human face verification abilities are currently beyond existing computer-based face verification algorithms [39]. This belief, however, is supported more by anecdotal impression than by scientific evidence. By contrast, there have already been a number of papers comparing human and computer-based face verification performance [2, 54, 40, 41, 38, 8]. It has been shown that the best current face verification algorithms perform better than humans in the good and moderate conditions. So, it is really not that difficult to beat human performance in some specific scenarios.
9. Conclusion and Future Work
This paper presents a principled Multi-Task Learning approach based on Discriminative Gaussian Process Latent Variable Model, named GaussianFace, for face verification by including a computationally more efficient equivalent form of KFDA and the multi-task learning constraint to the DGPLVM model. We use Gaussian Processes approximation and anchor graphs to speed up the inference and prediction of our model. Based on the GaussianFace model, we propose two different approaches for face verification. Extensive experiments on challenging datasets validate the efficacy of our model. The GaussianFace model finally surpassed human-level face verification accuracy, thanks to exploiting additional data from multiple source-domains to improve the generalization performance of face verification in the target-domain and adapting automatically to complex face variations. Although several techniques such as the Laplace approximation and anchor graph are introduced to speed up the process of inference and prediction in our GaussianFace model, it still takes a long time to train our model for the high performance. In addition, large memory is also necessary. Therefore, for specific application, one needs to balance the three dimensions: memory, running time, and performance. Generally speaking, higher performance requires more memory and more running time. In the future, the issue of running time can be further addressed by the distributed parallel algorithm or the GPU implementation of large matrix inversion. To address the issue of memory, some online algorithms for training need to be developed. Another more intuitive method is to seek a more efficient sparse representation for the large covariance matrix.