ForcedAlignerGrammar.java

/*
 * Copyright 1999-2002 Carnegie Mellon University.  
 * Portions Copyright 2002 Sun Microsystems, Inc.  
 * Portions Copyright 2002 Mitsubishi Electric Research Laboratories.
 * All Rights Reserved.  Use is subject to license terms.
 * 
 * See the file "license.terms" for information on usage and
 * redistribution of this file, and for a DISCLAIMER OF ALL 
 * WARRANTIES.
 *
 */

package edu.cmu.sphinx.linguist.language.grammar;

import edu.cmu.sphinx.util.LogMath;
import edu.cmu.sphinx.linguist.dictionary.Dictionary;

import java.util.StringTokenizer;

/**
 * Creates a grammar from a reference sentence. It is a constrained grammar that represents the sentence only.
 * <p>
 * Note that all grammar probabilities are maintained in the LogMath log base
 */

public class ForcedAlignerGrammar extends Grammar {

    protected GrammarNode finalNode;

    public ForcedAlignerGrammar(boolean showGrammar, boolean optimizeGrammar, boolean addSilenceWords, boolean addFillerWords, Dictionary dictionary) {
        super(showGrammar,optimizeGrammar,addSilenceWords,addFillerWords,dictionary);
    }

    public ForcedAlignerGrammar() {

    }


    /** Create class from reference text (not implemented). */
    @Override
    protected GrammarNode createGrammar() {
        throw new Error("Not implemented");
    }


    /** Creates the grammar */
    @Override
    protected GrammarNode createGrammar(String referenceText)
            throws NoSuchMethodException {

        initialNode = createGrammarNode(false);
        finalNode = createGrammarNode(true);
        createForcedAlignerGrammar(initialNode, finalNode, referenceText);

        return initialNode;
    }


    /**
     * Create a branch of the grammar that corresponds to a transcript.  For each word create a node, and link the nodes
     * with arcs.  The branch is connected to the initial node iNode, and the final node fNode.
     *
     * @param iNode initial node
     * @param fNode final node
     * @param transcript transcript
     * @return the first node of this branch
     */
    protected GrammarNode createForcedAlignerGrammar(GrammarNode iNode, GrammarNode fNode, String transcript) {
        final float logArcProbability = LogMath.LOG_ONE;

        StringTokenizer tok = new StringTokenizer(transcript);

        GrammarNode firstNode = null;
        GrammarNode lastNode = null;

        while (tok.hasMoreTokens()) {

            String token;
            token = tok.nextToken();

            GrammarNode prevNode = lastNode;
            lastNode = createGrammarNode(token);
            if (firstNode == null) firstNode = lastNode;

            if (prevNode != null) {
                prevNode.add(lastNode, logArcProbability);
            }
        }

        iNode.add(firstNode, logArcProbability);
        lastNode.add(fNode, logArcProbability);

        return firstNode;
    }
}