In file ../include/EST_viterbi.h:

class EST_Viterbi_Decoder

A class that offers a generalised Viterbi decoder.

Public Fields

EST_Features

f For holding vlaues to pass to user called functions

Public Methods

	EST_Viterbi_Decoder (uclist_f_t a, unpath_f_t b) Construct a decoder with given candidate function and join function, as number of states is given this implies a beam search
	EST_Viterbi_Decoder (uclist_f_t a, unpath_f_t b, int num_states) Construct a decoder with given candidate function and join function with a state size as specified
	~EST_Viterbi_Decoder ()
void	set_beam_width (int w) Only for use in beam search mode: number of paths to consider
void	set_cand_width (int w) Only for use in beam search mode: number of condidates to consider
void	set_debug (int d) Output some debugging information
void	set_big_is_good (int flag) Define is good scores are bigger or smaller.
EST_VTCandidate*	add_cand_prune (EST_VTCandidate* newcand, EST_VTCandidate* allcands) Add a new candidtate to list if better than others, pruning the list if required
void	initialise (EST_Relation* r) Build the initial table from a EST_Relation
void	set_pruning_parameters (float beam, float ob_beam) set beam widths for pruning
void	search (void) Do the the actual search
bool	result (const EST_String &n) Extract the result from the table and store it as a feature on the related EST_Item in the given EST_Relation named as n.
void	copy_feature (const EST_String &n) Copy named feature from the best path to related stream item

Public

	Unfortunately using MAX_DOUBLE doesn't do the right thing
	(eg.

Documentation

A class that offers a generalised Viterbi decoder.

This class can be used to find the best path through a set of candidates based on liklihoods of the candidates and some combination function. The candidate list and joining are not included in the decoder itself but are user defined functions that are specified as construction time.

Those functions need to return a list of candidates and score a join of a path to a candidate and (optionally define a state).

Although this offers a full Viterbi search it may also be used as a generalised beam search.

See viterbi_main.cc for an example of using this.

EST_Features f

For holding vlaues to pass to user called functions

Unfortunately using MAX_DOUBLE doesn't do the right thing

Unfortunately using MAX_DOUBLE doesn't do the right thing

(eg.

(eg. comparison don't work with MAX_DOUBLE on alphas), so

EST_Viterbi_Decoder(uclist_f_t a, unpath_f_t b)

Construct a decoder with given candidate function and join function, as number of states is given this implies a beam search

EST_Viterbi_Decoder(uclist_f_t a, unpath_f_t b, int num_states)

Construct a decoder with given candidate function and join function with a state size as specified

~EST_Viterbi_Decoder()

void set_beam_width(int w)

Only for use in beam search mode: number of paths to consider

void set_cand_width(int w)

Only for use in beam search mode: number of condidates to consider

void set_debug(int d)

Output some debugging information

void set_big_is_good(int flag)

Define is good scores are bigger or smaller. This allows the search to work for likelihoods probabailities, scores or whatever

EST_VTCandidate* add_cand_prune(EST_VTCandidate* newcand, EST_VTCandidate* allcands)

Add a new candidtate to list if better than others, pruning the list if required

void initialise(EST_Relation* r)

Build the initial table from a EST_Relation

void set_pruning_parameters(float beam, float ob_beam)

set beam widths for pruning

void search(void)

Do the the actual search

bool result(const EST_String &n)

Extract the result from the table and store it as a feature on the related EST_Item in the given EST_Relation named as n. Return FALSE if no path is found.

void copy_feature(const EST_String &n)

Copy named feature from the best path to related stream item

This class has no child classes.

Author:

Alan W Black (awb@cstr.ed.ac.uk): July 1996

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This page is part of the Edinburgh Speech Tools Library documentation
Copyright University of Edinburgh 1997
Contact: speech_tools@cstr.ed.ac.uk