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446 lines
13 KiB
C
446 lines
13 KiB
C
/* -*- c-basic-offset: 4; indent-tabs-mode: nil -*- */
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/* ====================================================================
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* Copyright (c) 2008 Carnegie Mellon University. All rights
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* reserved.
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*
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* Redistribution and use in source and binary forms, with or without
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* modification, are permitted provided that the following conditions
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* are met:
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*
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* 1. Redistributions of source code must retain the above copyright
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* notice, this list of conditions and the following disclaimer.
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*
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* 2. Redistributions in binary form must reproduce the above copyright
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* notice, this list of conditions and the following disclaimer in
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* the documentation and/or other materials provided with the
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* distribution.
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*
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* This work was supported in part by funding from the Defense Advanced
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* Research Projects Agency and the National Science Foundation of the
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* United States of America, and the CMU Sphinx Speech Consortium.
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*
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* THIS SOFTWARE IS PROVIDED BY CARNEGIE MELLON UNIVERSITY ``AS IS'' AND
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* ANY EXPRESSED OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO,
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* THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
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* PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL CARNEGIE MELLON UNIVERSITY
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* NOR ITS EMPLOYEES BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
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* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
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* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
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* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
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* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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*
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* ====================================================================
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*
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*/
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/**
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* @file ps_lattice.h Word graph search
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*/
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#ifndef __PS_LATTICE_H__
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#define __PS_LATTICE_H__
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/* SphinxBase headers. */
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#include <sphinxbase/prim_type.h>
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#include <sphinxbase/ngram_model.h>
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/* PocketSphinx headers. */
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#include <pocketsphinx_export.h>
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/**
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* Word graph structure used in bestpath/nbest search.
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*/
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typedef struct ps_lattice_s ps_lattice_t;
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/**
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* DAG nodes.
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*
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* A node corresponds to a number of hypothesized instances of a word
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* which all share the same starting point.
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*/
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typedef struct ps_latnode_s ps_latnode_t;
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/**
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* Iterator over DAG nodes.
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*/
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typedef struct ps_latnode_s ps_latnode_iter_t; /* pay no attention to the man behind the curtain */
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/**
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* Links between DAG nodes.
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*
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* A link corresponds to a single hypothesized instance of a word with
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* a given start and end point.
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*/
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typedef struct ps_latlink_s ps_latlink_t;
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/**
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* Iterator over DAG links.
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*/
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typedef struct latlink_list_s ps_latlink_iter_t;
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/* Forward declaration needed to avoid circular includes */
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struct ps_decoder_s;
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/**
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* Read a lattice from a file on disk.
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*
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* @param ps Decoder to use for processing this lattice, or NULL.
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* @param file Path to lattice file.
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* @return Newly created lattice, or NULL for failure.
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*/
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POCKETSPHINX_EXPORT
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ps_lattice_t *ps_lattice_read(struct ps_decoder_s *ps,
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char const *file);
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/**
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* Retain a lattice.
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*
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* This function retains ownership of a lattice for the caller,
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* preventing it from being freed automatically. You must call
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* ps_lattice_free() to free it after having called this function.
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*
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* @return pointer to the retained lattice.
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*/
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POCKETSPHINX_EXPORT
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ps_lattice_t *ps_lattice_retain(ps_lattice_t *dag);
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/**
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* Free a lattice.
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*
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* @return new reference count (0 if dag was freed)
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*/
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POCKETSPHINX_EXPORT
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int ps_lattice_free(ps_lattice_t *dag);
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/**
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* Write a lattice to disk.
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*
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* @return 0 for success, <0 on failure.
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*/
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POCKETSPHINX_EXPORT
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int ps_lattice_write(ps_lattice_t *dag, char const *filename);
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/**
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* Write a lattice to disk in HTK format
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*
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* @return 0 for success, <0 on failure.
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*/
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POCKETSPHINX_EXPORT
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int ps_lattice_write_htk(ps_lattice_t *dag, char const *filename);
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/**
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* Get the log-math computation object for this lattice
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*
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* @return The log-math object for this lattice. The lattice retains
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* ownership of this pointer, so you should not attempt to
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* free it manually. Use logmath_retain() if you wish to
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* reuse it elsewhere.
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*/
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POCKETSPHINX_EXPORT
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logmath_t *ps_lattice_get_logmath(ps_lattice_t *dag);
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/**
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* Start iterating over nodes in the lattice.
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*
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* @note No particular order of traversal is guaranteed, and you
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* should not depend on this.
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*
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* @param dag Lattice to iterate over.
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* @return Iterator over lattice nodes.
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*/
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POCKETSPHINX_EXPORT
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ps_latnode_iter_t *ps_latnode_iter(ps_lattice_t *dag);
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/**
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* Move to next node in iteration.
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* @param itor Node iterator.
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* @return Updated node iterator, or NULL if finished
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*/
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POCKETSPHINX_EXPORT
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ps_latnode_iter_t *ps_latnode_iter_next(ps_latnode_iter_t *itor);
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/**
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* Stop iterating over nodes.
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* @param itor Node iterator.
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*/
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POCKETSPHINX_EXPORT
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void ps_latnode_iter_free(ps_latnode_iter_t *itor);
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/**
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* Get node from iterator.
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*/
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POCKETSPHINX_EXPORT
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ps_latnode_t *ps_latnode_iter_node(ps_latnode_iter_t *itor);
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/**
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* Get start and end time range for a node.
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*
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* @param node Node inquired about.
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* @param out_fef Output: End frame of first exit from this node.
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* @param out_lef Output: End frame of last exit from this node.
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* @return Start frame for all edges exiting this node.
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*/
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POCKETSPHINX_EXPORT
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int ps_latnode_times(ps_latnode_t *node, int16 *out_fef, int16 *out_lef);
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/**
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* Get word string for this node.
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*
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* @param dag Lattice to which node belongs.
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* @param node Node inquired about.
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* @return Word string for this node (possibly a pronunciation variant).
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*/
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POCKETSPHINX_EXPORT
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char const *ps_latnode_word(ps_lattice_t *dag, ps_latnode_t *node);
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/**
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* Get base word string for this node.
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*
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* @param dag Lattice to which node belongs.
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* @param node Node inquired about.
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* @return Base word string for this node.
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*/
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POCKETSPHINX_EXPORT
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char const *ps_latnode_baseword(ps_lattice_t *dag, ps_latnode_t *node);
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/**
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* Iterate over exits from this node.
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*
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* @param node Node inquired about.
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* @return Iterator over exit links from this node.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_iter_t *ps_latnode_exits(ps_latnode_t *node);
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/**
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* Iterate over entries to this node.
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*
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* @param node Node inquired about.
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* @return Iterator over entry links to this node.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_iter_t *ps_latnode_entries(ps_latnode_t *node);
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/**
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* Get best posterior probability and associated acoustic score from a lattice node.
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*
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* @param dag Lattice to which node belongs.
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* @param node Node inquired about.
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* @param out_link Output: exit link with highest posterior probability
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* @return Posterior probability of the best link exiting this node.
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* Log is expressed in the log-base used in the decoder. To
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* convert to linear floating-point, use
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* logmath_exp(ps_lattice_get_logmath(), pprob).
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*/
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POCKETSPHINX_EXPORT
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int32 ps_latnode_prob(ps_lattice_t *dag, ps_latnode_t *node,
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ps_latlink_t **out_link);
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/**
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* Get next link from a lattice link iterator.
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*
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* @param itor Iterator.
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* @return Updated iterator, or NULL if finished.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_iter_t *ps_latlink_iter_next(ps_latlink_iter_t *itor);
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/**
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* Stop iterating over links.
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* @param itor Link iterator.
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*/
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POCKETSPHINX_EXPORT
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void ps_latlink_iter_free(ps_latlink_iter_t *itor);
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/**
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* Get link from iterator.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_latlink_iter_link(ps_latlink_iter_t *itor);
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/**
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* Get start and end times from a lattice link.
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*
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* @note these are <strong>inclusive</strong> - i.e. the last frame of
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* this word is ef, not ef-1.
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*
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* @param link Link inquired about.
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* @param out_sf Output: (optional) start frame of this link.
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* @return End frame of this link.
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*/
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POCKETSPHINX_EXPORT
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int ps_latlink_times(ps_latlink_t *link, int16 *out_sf);
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/**
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* Get destination and source nodes from a lattice link
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*
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* @param link Link inquired about
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* @param out_src Output: (optional) source node.
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* @return destination node
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*/
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POCKETSPHINX_EXPORT
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ps_latnode_t *ps_latlink_nodes(ps_latlink_t *link, ps_latnode_t **out_src);
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/**
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* Get word string from a lattice link.
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*
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* @param dag Lattice to which node belongs.
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* @param link Link inquired about
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* @return Word string for this link (possibly a pronunciation variant).
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*/
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POCKETSPHINX_EXPORT
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char const *ps_latlink_word(ps_lattice_t *dag, ps_latlink_t *link);
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/**
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* Get base word string from a lattice link.
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*
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* @param dag Lattice to which node belongs.
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* @param link Link inquired about
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* @return Base word string for this link
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*/
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POCKETSPHINX_EXPORT
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char const *ps_latlink_baseword(ps_lattice_t *dag, ps_latlink_t *link);
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/**
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* Get predecessor link in best path.
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*
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* @param link Link inquired about
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* @return Best previous link from bestpath search, if any. Otherwise NULL
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_latlink_pred(ps_latlink_t *link);
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/**
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* Get acoustic score and posterior probability from a lattice link.
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*
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* @param dag Lattice to which node belongs.
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* @param link Link inquired about
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* @param out_ascr Output: (optional) acoustic score.
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* @return Posterior probability for this link. Log is expressed in
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* the log-base used in the decoder. To convert to linear
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* floating-point, use logmath_exp(ps_lattice_get_logmath(), pprob).
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*/
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POCKETSPHINX_EXPORT
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int32 ps_latlink_prob(ps_lattice_t *dag, ps_latlink_t *link, int32 *out_ascr);
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/**
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* Create a directed link between "from" and "to" nodes, but if a link already exists,
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* choose one with the best link_scr.
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*/
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POCKETSPHINX_EXPORT
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void ps_lattice_link(ps_lattice_t *dag, ps_latnode_t *from, ps_latnode_t *to,
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int32 score, int32 ef);
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/**
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* Start a forward traversal of edges in a word graph.
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*
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* @note A keen eye will notice an inconsistency in this API versus
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* other types of iterators in PocketSphinx. The reason for this is
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* that the traversal algorithm is much more efficient when it is able
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* to modify the lattice structure. Therefore, to avoid giving the
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* impression that multiple traversals are possible at once, no
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* separate iterator structure is provided.
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*
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* @param dag Lattice to be traversed.
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* @param start Start node (source) of traversal.
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* @param end End node (goal) of traversal.
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* @return First link in traversal.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_lattice_traverse_edges(ps_lattice_t *dag, ps_latnode_t *start, ps_latnode_t *end);
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/**
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* Get the next link in forward traversal.
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*
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* @param dag Lattice to be traversed.
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* @param end End node (goal) of traversal.
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* @return Next link in traversal.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_lattice_traverse_next(ps_lattice_t *dag, ps_latnode_t *end);
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/**
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* Start a reverse traversal of edges in a word graph.
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*
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* @note See ps_lattice_traverse_edges() for why this API is the way it is.
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*
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* @param dag Lattice to be traversed.
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* @param start Start node (goal) of traversal.
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* @param end End node (source) of traversal.
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* @return First link in traversal.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_lattice_reverse_edges(ps_lattice_t *dag, ps_latnode_t *start, ps_latnode_t *end);
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/**
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* Get the next link in reverse traversal.
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*
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* @param dag Lattice to be traversed.
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* @param start Start node (goal) of traversal.
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* @return Next link in traversal.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_lattice_reverse_next(ps_lattice_t *dag, ps_latnode_t *start);
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/**
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* Do N-Gram based best-path search on a word graph.
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*
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* This function calculates both the best path as well as the forward
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* probability used in confidence estimation.
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*
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* @return Final link in best path, NULL on error.
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*/
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POCKETSPHINX_EXPORT
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ps_latlink_t *ps_lattice_bestpath(ps_lattice_t *dag, ngram_model_t *lmset,
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float32 lwf, float32 ascale);
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/**
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* Calculate link posterior probabilities on a word graph.
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*
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* This function assumes that bestpath search has already been done.
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*
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* @return Posterior probability of the utterance as a whole.
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*/
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POCKETSPHINX_EXPORT
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int32 ps_lattice_posterior(ps_lattice_t *dag, ngram_model_t *lmset,
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float32 ascale);
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/**
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* Prune all links (and associated nodes) below a certain posterior probability.
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*
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* This function assumes that ps_lattice_posterior() has already been called.
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*
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* @param beam Minimum posterior probability for links. This is
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* expressed in the log-base used in the decoder. To convert
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* from linear floating-point, use
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* logmath_log(ps_lattice_get_logmath(), prob).
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* @return number of arcs removed.
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*/
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POCKETSPHINX_EXPORT
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int32 ps_lattice_posterior_prune(ps_lattice_t *dag, int32 beam);
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#ifdef NOT_IMPLEMENTED_YET
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/**
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* Expand lattice using an N-gram language model.
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*
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* This function expands the lattice such that each node represents a
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* unique N-gram history, and adds language model scores to the links.
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*/
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POCKETSPHINX_EXPORT
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int32 ps_lattice_ngram_expand(ps_lattice_t *dag, ngram_model_t *lm);
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#endif
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/**
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* Get the number of frames in the lattice.
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*
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* @param dag The lattice in question.
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* @return Number of frames in this lattice.
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*/
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POCKETSPHINX_EXPORT
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int ps_lattice_n_frames(ps_lattice_t *dag);
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#endif /* __PS_LATTICE_H__ */
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