Janus Recognition Toolkit

The Janus Recognition Toolkit (JRTk) is a general-purpose speech recognition toolkit developed at the Interactive Systems Labs at Carnegie Mellon University and Karlsruhe Institute of Technology. Commercial and research liscenses are available.


The Janus Recognition Toolkit (JRTk) is a general-purpose speech recognition toolkit useful for both research and application development and is part of the JANUS speech-to-speech translation system.

The JRTk provides a flexible Tcl/Tk script based environment which enables researchers to build state-of-the-art speech recognizers and allows them to develop, implement, and evaluate new methods. It implements an object oriented approach that unlike other toolkits is not a set of libraries and precompiled modules but a programmable shell with transparent, yet efficient objects.


Since version 5 JRTk features the IBIS decoder, a one-pass decoder that is based on a re-entrant single pronunciation prefix tree and makes use of the concept of linguistic context polymorphism. It is therefore able to incorporate full linguistic knowledge at an early stage. It is possible to decode in one pass, using the same engine in combination with a statistical n-gram language model as well as context- free grammars. It is also possible to use the decoder to rescore lattices in a very efficient way.



JRTk features state-of-the art techniques for pre-processing, acoustic modeling, and search.


Acoustic Pre-Processing

  • Processing of various, frequent audio formats
  • Flexible short-term fourier analysis
  • Flexibly configurable Mel-frequency scaled cepstral coefficients calculation
  • Minimimum variance distortion response processing
  • LPC processing
  • Mean and variance normalization

Acoustic Modeling

  • EM Training, label training, Viterbi training
  • incremental growing of Gaussians
  • Semi-tied covariances
  • MMIE training, bMMIE training
  • Speaker adaptive training


  • Single pass decoder
  • Flexible language model interface for n-gram language models and grammars
  • lattice generation and manipulation
  • lattice rescoring
  • consensus decoding
  • confusion network combination


The JRTk is used for speech recognition in many on-going projects as well as past ones.

Current Projects


Past Projects


License Information

The JRTk is liscensed by Carnegie Mellon University. Commercial as well as research liscenses are available. Terms and conditions as well as further information can be inquired by contacting Prof. Alex Waibel at ahw∂cs.cmu.edu.



JRTk Articles
Title Author Source

Hagen Soltau, Florian Metze, Christian Fügen, Alex Waibel

Automatic Speech Recognition and Understanding Workshop 2001, ASRU 2001, Trento, Italy, 25. October 2011

Monika Woszczyna, N. Aoki-Waibel, Finn Dag Buø, Noah Coccaro, Keiko Horiguchi, Thomas Kemp, Alon Lavie, Arthur McNair, Thomas Polzin, Ivica Rogina, Carolyn Rose, Tanja Schultz, Bernhard Suhm, M. Tomita, Alex Waibel 

International Conference on Acoustics, Speech, and Signal Processing 1994, ICASSP 1994, Adelaide, Australia, 01. April 1994