lm.c

WinCE平台上的语音识别程序

/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */
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 * This work was supported in part by funding from the Defense Advanced 
 * Research Projects Agency and the National Science Foundation of the 
 * United States of America, and the CMU Sphinx Speech Consortium.
 *
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/*
 * lm.c -- Interpolation of various language models.
 *
 * HISTORY
 * 
 * 01-Apr-97	M K Ravishankar (rkm@cs) at Carnegie Mellon University
 * 		Started, based on earlier FBS6 version.
 */


/* Currently, interpolation of dynamic cache LM and static trigram LM */

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>

#include "s2types.h"
#include "basic_types.h"
#include "list.h"
#include "lmclass.h"
#include "lm_3g.h"
#include "lm.h"
#include "cache_lm.h"
#include "search_const.h"
#include "msd.h"
#include "dict.h"
#include "kb.h"
#include "err.h"
#include "log.h"

static cache_lm_t *clm = NULL;

int32
lm_tg_score(int32 w1, int32 w2, int32 w3)
{
    int32 cscr, tscr, remwt;
    lm_t *lm3g;

    if (!clm)
        return (lm3g_tg_score(w1, w2, w3));

    lm3g = lm_get_current();

    /* Get cache LM score and apply language weight */
    cscr = cache_lm_score(clm, w2, w3, &remwt);
    cscr = LWMUL(cscr, lm3g->lw);

    /* Get static trigram LM score, apply remaining weight */
    tscr = lm3g_tg_score(w1, w2, w3);
    tscr += LWMUL(remwt, lm3g->lw);

    /* Return MAX of static trigram LM and dynamic cache LM scores (approx to sum) */
    return (cscr > tscr) ? cscr : tscr;
}

int32
lm_bg_score(int32 w1, int32 w2)
{
    int32 cscr, tscr, remwt;
    lm_t *lm3g;

    if (!clm)
        return (lm3g_bg_score(w1, w2));

    lm3g = lm_get_current();

    /* Get cache LM score and apply language weight */
    cscr = cache_lm_score(clm, w1, w2, &remwt);
    cscr = LWMUL(cscr, lm3g->lw);

    /* Get static trigram LM score, apply remaining weight */
    tscr = lm3g_bg_score(w1, w2);
    tscr += LWMUL(remwt, lm3g->lw);

    /* Return MAX of static trigram LM and dynamic cache LM scores (approx to sum) */
    return (cscr > tscr) ? cscr : tscr;
}

int32
lm_ug_score(int32 w)
{
    return (lm3g_ug_score(w));
}

void
lm_cache_lm_init(void)
{
    if (clm)
        return;

    /* Hack!!  Hardwired parameters to cache_lm_init */
    clm = cache_lm_init(0.0001, 0.001, 0.04, 100, 0.07);
}

void
lm_cache_lm_add_ug(int32 w)
{
    int32 ugscr;
    lm_t *lm3g;

    if (!clm)
        return;

    lm3g = lm_get_current();
    ugscr = lm3g_ug_score(w);
    ugscr = LWMUL(ugscr, lm3g->invlw);
    if (ugscr >= clm->ugprob_thresh)
        return;
#if 0
    E_INFO("Adding unigram %s (scr %d, thresh %d) to cache LM\n",
           kb_get_word_str(w), ugscr, clm->ugprob_thresh);
#endif
    cache_lm_add_ug(clm, w);
}

void
lm_cache_lm_add_bg(int32 w1, int32 w2)
{
    if (!clm)
        return;
#if 0
    E_INFO("Adding bigram %s,%s to cache LM\n",
           kb_get_word_str(w1), kb_get_word_str(w2));
#endif
    cache_lm_add_bg(clm, w1, w2);
}

void
lm_cache_lm_dump(char *file)
{
    if (!clm)
        return;
    cache_lm_dump(clm, file);
}

void
lm_cache_lm_load(char *file)
{
    if (!clm)
        return;
    cache_lm_load(clm, file);
}