outprob_style.c File Reference

Compute output probability of a state on lexicon tree. More...

#include <julius.h>

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Functions
void	outprob_style_cache_init (WCHMM_INFO *wchmm)
LOGPROB	outprob_style (WCHMM_INFO *wchmm, int node, int last_wid, int t, HTK_Param *param)
void	error_missing_right_triphone (HMM_Logical *base, char *rc_name)
void	error_missing_left_triphone (HMM_Logical *base, char *lc_name)
Variables
static char	rbuf [MAX_HMMNAME_LEN]
	Local workarea for HMM name conversion.

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Detailed Description

Compute output probability of a state on lexicon tree.

Author:

Akinobu Lee

Date:

Mon Aug 22 17:14:26 2005

These functions compute the output probability of an input vector from a state on the lexicon tree.

When using triphone acoustic model, the cross-word triphone handling is done here. The head and tail phoneme of every words has corresponding pseudo phone set on the tree lexicon, so the actual likelihood computation will be done as the following:

1. word-internal: compute as normal.
2. Word head phone: the correct triphone phone, according to the last word information on the passing token, will be dynamically assigned to compute the cross-word dependency.
3. Word tail phone: all the states in the pseudo phone set (they are states of triphones that has the same left context as the word end) will be computed, and use
   • maximum value if "-iwcd1 max" specified, or
   • average value if "-iwcd1 avg" specified, or
   • average of best N states if "-iwcd1 best N" specified (default: 3) the actual pseudo phoneset computation will be done in outprob_cd().
4. word with only one state: both of above should be considered.

To denote which operation to do for a state, AS_Style ID is assigned to each state.

The triphone transformation, that will be performed on the state of 2 and 4 above, will be cached on the tree lxicon by each state per frame, to suppress computation overhead.

Revision

1.1.1.1

Definition in file outprob_style.c.

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Function Documentation

void outprob_style_cache_init (  WCHMM_INFO *  wchmm  )

Initialize cache for triphone alternation on word head. Parameters: wchmm  [i/o] tree lexicon Definition at line 99 of file outprob_style.c. Referenced by init_nodescore().

LOGPROB outprob_style (  WCHMM_INFO *  wchmm, int  node, int  last_wid, int  t, HTK_Param *  param )

Calculate output log probability of an input vector on time frame t in input paramter param at a node on tree lexicon. Parameters: wchmm  [in] tree lexicon structure node  [in] node ID to compute the output probability last_wid  [in] word ID of last word hypothesis (used when the node is within the word beginning phone and triphone is used. t  [in] time frame of input vector in param to compute. param  [in] input parameter structure Returns: the computed log probability. Definition at line 383 of file outprob_style.c. Referenced by bt_discount_pescore(), get_back_trellis_proceed(), and init_nodescore().

void error_missing_right_triphone (  HMM_Logical *  base, char *  rc_name )

Output error message when a triphone with the specified right context is not defined. Parameters: base  [in] base triphone rc_name  [in] name of right context phone Definition at line 542 of file outprob_style.c. Referenced by next_word(), and scan_word().

void error_missing_left_triphone (  HMM_Logical *  base, char *  lc_name )

Output error message when a triphone with the specified right context is not defined. Parameters: base  [in] base triphone lc_name  [in] name of left context phone Definition at line 567 of file outprob_style.c. Referenced by outprob_style(), and scan_word().

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