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An Open Source WFST based Speech Recognition Decoder

OpenDcd - An Open Source WFST based Speech Recognition Decoder

OpenDcd a lightweight and portable WFST based speech decoding toolkit written in C++. OpenDcd provides a set of tools for decoding, cascade construction and hypothesis post- processing. The focus of the toolkit is to provide a foundation for research into new decoding methods that can be deployed. Through the use of C++ templates the core decoder can be configured and extended in many ways. For example selecting different on-the-fly composition or lattice generation strategies. The core engine has detailed profiling, logging and analysis methods that make it highly for deployement in production systems. The toolkit makes used of OpenFst for representing and manipulating the models. It is distributed as an open source project with an Apache Licence.

For more information see the main documentation site, and the tutorial for installing the OpenDcd and decoding using the Librispeech corpus and models from kaldi-asr.og.

Quick Installation Guide

    git clone
    cd src/bin

Kaldi Conversion Quick Start

For Kaldi model converion and decoding a working Kaldi installation and set of acoustic and language models and features from generated from a Kaldi egs/s5 script are required. The following example is based on the output of Kaldi WSJ training run.

Graph construction, the scripts directory contains The Kaldi language directory, we re-use the existing Kaldi lexicon and LM.

    cd $OPENDCD/scripts
    export KALDI_ROOT=/home/opendcd/tools/kaldi-trunk
    ./ \
    $KALDI_ROOT/egs/wsj/s5/data/lang_test_bg_5k \
    $KALDI_ROOT/egs/wsj/s5/exp/tri2a \
    $KALDI_ROOT/egs/wsj/s5/exp/ocd_tri2a \

See egs directory contains example script for showing how to convert a Kaldi WSJ setup

Brief Overview

The first release includes the following features:


Cascde construction:

Results post-processing:

Kaldi Interoperability:

More Information