SqueezedText: A Real-Time Scene Text Recognition by Binary Convolutional Encoder-Decoder Network

A new approach for real-time scene text recognition is proposed in this paper. A novel binary convolutional encoderdecoder network (B-CEDNet) together with a bidirectional recurrent neural network (Bi-RNN). The B-CEDNet is engaged as a visual front-end to provide elaborated character detection, and a back-end Bi-RNN performs characterlevel sequential correction and classification based on learned contextual knowledge. The front-end B-CEDNet can process multiple regions containing characters using a one-off forward operation, and is trained under binary constraints with significant compression. Hence it leads to both remarkable inference run-time speedup as well as memory usage reduction. With the elaborated character detection, the back-end Bi-RNN merely processes a low dimension feature sequence with category and spatial information of extracted characters for sequence correction and classification. By training with over 1,000,000 synthetic scene text images, the B-CEDNet achieves a recall rate of 0.86, precision of 0.88 and F-score of 0.87 on ICDAR-03 and ICDAR-13. With the correction and classification by Bi-RNN, the proposed real-time scene text recognition achieves state-of-the-art accuracy while only consumes less than 1-ms inference run-time. The flow processing flow is realized on GPU with a small network size of 1.01 MB for B-CEDNet and 3.23 MB for Bi-RNN, which is much faster and smaller than the existing solutions. Introduction The success of convolutional neural network (CNN) has resulted in a potential general machine learning engine for various computer vision applications (LeCun et al. 1998; Krizhevsky, Sutskever, and Hinton 2012), such as text detection, recognition and interpretation from images. Applications, such as Advanced Driver Assistance System (ADAS) for road signs with text, however, require a real-time processing capability that is beyond the existing approaches (Jaderberg et al. 2014; Jaderberg, Vedaldi, and Zisserman 2014) in terms of processing functionality, efficiency and latency. For a real-time scene text recognition application, one needs a method with memory efficiency and fast processing time. In this paper, we reveal that binary features (Courbariaux and Bengio 2016) can effectively and efficiently Copyright c © 2018, Association for the Advancement of Artificial Intelligence (www.aaai.org). All rights reserved. represent the scene text image. Combining with deconvolution technique, we introduce a binary convolutional encoderdecoder network (B-CEDNet) for real-time one-shot character detection and recognition. The scene text recognition is further enhanced with a back-end character-level sequential correction and classification, based on a bidirectional recurrent neural network (Bi-RNN). Instead of detecting characters sequentially (Bissacco et al. 2013; Wang et al. 2012; Shi, Bai, and Yao 2015), our proposed method, called SqueezedText, can detect multiple characters simultaneously and extracts a length-variable character sequence with corresponding spatial information. This sequence will be subsequently fed into a Bi-RNN, which then learns the detection error characteristics from the previous stage to provides characterlevel correction and classification based on the spatial and contextual cues. By training with over 1,000,000 synthetic scene text images, the proposed SqueezedText can achieve recall rate of 0.86, precision of 0.88 and F-score of 0.87 on ICDAR-03 (Lucas et al. 2003) dataset. More importantly, it achieves state-of-the-art accuracy of 93.8%, 92.7%, 94.3% 96.1% and 83.6% on ICDAR-03, ICDAR-13, IIIT5K, STV and Synthe90K datasets. SqueezedText is realized on GPU with a small network size of 1.01 MB for B-CEDNet and 3.23 MB for Bi-RNN; and consumes less than 1 ms inference runtime on average. It is up to 4× faster and 6× smaller than state-of-the-art work. The contributions of this paper are summarized as follows: • We propose a novel binary convolutional encoder-decoder neural network model, which acts as a visual front-end module to provide unconstrained scene text detection and recognition. It effectively detects individual character with high recall rate, realizing an extremely fast run-time speed and small memory consumption. • We reveal that the text features can be learned and encoded in binary format without loss of discriminative information. This information can be further decoded and recovered to perform multi-character detection and recognition in parallel. • We further design a back-end bidirectional RNN (BiRNN) to provide fast and robust scene text recognition with correction and classification.