Exploiting image translations via ensemble self-supervised learning for Unsupervised Domain Adaptation

Unsupervised Domain Adaptation (UDA) aims to improve the generalization capacity of models when they are tested on a real-world target domain by learning a model on a source labeled domain. Recently, a UDA method was proposed that addresses the adaptation problem by combining ensemble learning with self-supervised learning. However, this method uses only the source domain to pretrain the model and employs a limited amount of classifiers to create target pseudo labels. To mitigate these deficiencies, in this work, we explore the usage of image translations in combination with ensemble learning and self-supervised learning. To increase the model’s exposure to more variable pretraining data, our method creates multiple diverse image translations, which encourages the learning of domain-invariant features, desired to increase generalization. With these image translations, we are able to learn translation-specific classifiers, which also allows to maximize the amount of ensemble’s classifiers resulting in more robust target pseudo labels. In addition, we propose to use the target domain in pretraining stage to mitigate source domain bias in the network. We evaluate our method on the standard UDA benchmarks, i.e., adapting GTA V and Synthia to Cityscapes, and achieve state-of-the-art results on the mIoU metric. Extensive ablation experiments are reported to highlight the advantageous properties of our UDA strategy.