Julius is an open source speech recognition engine. Julius is a high-performance, two-pass large vocabulary continuous speech recognition (LVCSR) decoder software for speech-related researchers and developers. Based on word 3-gram and context-dependent HMM, it can perform almost real-time decoding on most current PCs in 20k word dictation task. Major search techniques are fully incorporated. It is also modularized carefully to be independent from model structures, and various HMM types are supported such as shared-state triphones and tied-mixture models, with any number of mixtures, states, or phones. Standard formats are adopted to cope with other free modeling toolkit. The main platform is Linux and other Unix workstations, and also works on Windows. Julius is open source and distributed with a revised BSD style license. Julius has been developed as part of a free software toolkit for Japanese LVCSR research since 1997, and the work has been continued at Continuous Speech Recognition Consortium (CSRC), Japan from 2000 to 2003. From rev.3.4, a grammar-based recognition parser named "Julian" is integrated into Julius. Julian is a modified version of Julius that uses hand-designed DFA grammar as a language model. It can be used to build a kind of voice command system of small vocabulary, or various spoken dialogue tasks.
About Models
To run the Julius recognizer, you need a language model and an acoustic model for your language. Julius adopts acoustic models in HTK ASCII format, pronunciation dictionary in HTK-like format, and word 3-gram language models in ARPA standard format (forward 2-gram and reverse 3-gram as trained from speech corpus with reversed word order). Although Julius is only distributed with Japanese models, the VoxForge project is working on creating English acoustic models for use with the Julius Speech Recognition Engine.
