Context Perception Parallel Decoder for Scene Text Recognition.

Scene text recognition (STR) methods have struggled to attain high accuracy and fast inference speed. Auto-Regressive (AR)-based models implement the recognition in a character-by-character manner, showing superiority in accuracy but with slow inference speed. Alternatively, Parallel Decoding (PD)-based models infer all characters in a single decoding pass, offering faster inference speed but generally worse accuracy. To realize the dual goals of "AR-level accuracy and PD-level speed", we propose a Context Perception Parallel Decoder (CPPD) to perceive the related context and predict the character sequence in a PD pass. CPPD devises a character counting module to infer the occurrence count of each character, and a character ordering module to deduce the content-free reading order and positions. Meanwhile, the character prediction task associates the positions with characters. They together build a comprehensive recognition context, which benefits the decoder to focus accurately on characters with the attention mechanism, thereby improving the recognition accuracy. We construct a series of CPPD models and also plug the proposed modules into existing STR decoders. Experiments on both English and Chinese benchmarks demonstrate that the CPPD models achieve highly competitive accuracy while running much faster than existing leading models. Moreover, the plugged models achieve significant accuracy improvements.