RESPITE: The CASA Toolkit Page: Documentation: Block Library Index:HMMDecoderMD


The HMMDecoderMD is an extended version of the previously described HMMDecoderStandard that has been adapted to handle missing data. As well as an input stream of feature vectors, it also accepts a `missing data mask' (in2) and optional lower and upper bound values (in3 and in4). The vectors composing the mask and the bounds should have the same width as the feature vectors. The missing data mask should be a vector of boolean values. Each boolean element dictates whether the corresponding feature vector element is to be considered to be present (i.e. to contain reliable data) or to be missing (i.e. to contain unreliable data). Present values are indicated by 1's, and missing values by 0's.

The HMMDecoderMD has the same parameters as the HMMDecoderStandard, plus the two additional parameters that are described below:

As with HMMDecoderStandard, the missing data decoder outputs a stream of state-likelihood frames and a stream of mixture labels. Each state-likelihood frame consists of the likelihood of each model state having generated the corresponding input feature frame. Within these frames the state likelihoods occur in the same order in which the states are defined in the HMM definition file. (The mixture label frames (out2) indicate the integer label of the winning mixture for each state).

Inputs Meaning Sample 1-D frame $\ge$2-D frame
in1 feature vectors No Yes No
in2 missing data mask No Yes No
(in3) lower bound No Yes No
(in4) upper bound No Yes No

Outputs Meaning
out1state likelihoods
out2state max mixture label

Parameters Type Default Meaning
LOG_FILE String - Name of an optional log file
LOG_FILE_2 String - Name of additional detailed log file
WORD_PENALTY Float 0.0 The creation penalty
HMM_FILE String - Name of the HMM file list
GRAMMAR_FILE String - File storing the grammar
LABEL_FILE String - File storing HMM NAME-> HMM LABEL mapping
FIRST_TOKEN String - Label of a fixed first token
FINAL_TOKEN String - Label of a fixed final token
TRANSCRIPTION String - The correct transcription
SILENCE String "" The silence label(s)
MAX_APPROX Boolean False Use max mixture approximation
NBEST Int 1 Return best N hypotheses
STATE_PATH Boolean False Record HMM state path
HAS_DELTAS Boolean 0 Models have delta parameters
USE_DELTAS Boolean - Models have delta parameters
HYPOTHESIS FILTER String "" Regular expression for filtering hypotheses
OUTPUT_CONFUSIONS Boolean 0 Output confusion matrix
DUMP_PARAMETERS Boolean 0 Write parameters to log file
USE_BOUNDS Boolean False Use bounded marginalisation (static features)
USE_DELTA_BOUNDS Boolean False Use bounded marginalisation (delta features)

Documentation for CTKv1.1.4 - Last modified: Mon Jul 2 18:19:02 BST 2001