A Comparative Study of Attention-Based Encoder-Decoder Approaches to Natural Scene Text Recognition

Attention-based encoder-decoder approaches have shown promising results in scene text recognition. In the literature, models with different encoders, decoders and attention mechanisms have been proposed and compared on isolated word recognition tasks, where the models are trained on either synthetic word images or a small set of real-world images. In this paper, we investigate different components of the attention based framework and compare its performance with a CNN-DBLSTM-CTC based approach on large-scale real-world scene text sentence recognition tasks. We train character models by using more than 1.6M real-world text lines and compare their performance on test sets collected from a variety of real-world scenarios. Our results show that (1) attention on a two-dimensional feature map can yield better performance than one-dimensional one and an RNN based decoder performs better than CNN based one; (2) attention-based approaches can achieve higher recognition accuracy than CNN-DBLSTM-CTC based approaches on isolated word recognition tasks, but perform worse on sentence recognition tasks; (3) it is more effective and efficient for CNN-DBLSTM-CTC based approaches to leverage an explicit language model to boost recognition accuracy.