The HTK Book Steve Young Gunnar Evermann Dan Kershaw ...
Share Embed Flag
Download ePaper

The HTK Book Steve Young Gunnar Evermann Dan Kershaw ...

The HTK Book Steve Young Gunnar Evermann Dan Kershaw ... The HTK Book Steve Young Gunnar Evermann Dan Kershaw ...

old.site.clsp.jhu.edu
from old.site.clsp.jhu.edu More from this publisher
12.07.2015 Views

17.17 HRest 27717.17 HRest17.17.1 FunctionHRest performs basic Baum-Welch re-estimation of the parameters of a single HMM using a setof observation sequences. HRest can be used for normal isolated word training in which theobservation sequences are realisations of the corresponding vocabulary word.Alternatively, HRest can be used to generate seed HMMs for phoneme-based recognition. Inthis latter case, the observation sequences will consist of segments of continuously spoken trainingmaterial. HRest will cut these out of the training data automatically by simply giving it a segmentlabel.In both of the above applications, HRest is intended to operate on HMMs with initial parametervalues estimated by HInit.HRest supports multiple mixture components, multiple streams, parameter tying within asingle model, full or diagonal covariance matrices, tied-mixture models and discrete models. Theoutputs of HRest are often further processed by HERest.Like all re-estimation tools, HRest allows a floor to be set on each individual variance bydefining a variance floor macro for each data stream (see chapter 8). If any diagonal covariancecomponent falls below 0.00001, then the corresponding mixture weight is set to zero. A warning isissued if the number of mixtures is greater than one, otherwise an error occurs. Applying a variancefloor via the -v option or a variance floor macro can be used to prevent this.17.17.2 UseHRest is invoked via the command lineHRest [options] hmm trainFiles ...This causes the parameters of the given hmm to be re-estimated repeatedly using the data intrainFiles until either a maximum iteration limit is reached or the re-estimation converges. TheHMM definition can be contained within one or more macro files loaded via the standard -H option.Otherwise, the definition will be read from a file called hmm. The list of train files can be stored ina script file if required.The detailed operation of HRest is controlled by the following command line options-c f Set the threshold for tied-mixture observation pruning to f. When all mixtures of all modelsare tied to create a full tied-mixture system, the calculation of output probabilities is treated asa special case. Only those mixture component probabilities which fall within f of the maximummixture component probability are used in calculating the state output probabilities (default10.0).-e f This sets the convergence factor to the real value f. The convergence factor is the relativechange between successive values of P (O|λ) (default value 0.0001).-i N This sets the maximum number of re-estimation cycles to N (default value 20).-l s The string s must be the name of a segment label. When this option is used, HRest searchesthrough all of the training files and cuts out all segments with the given label. When thisoption is not used, HRest assumes that each training file is a single token.-m N Sets the minimum number of training examples to be N. If fewer than N examples are suppliedthen an error is reported (default value 3).-t Normally, training sequences are rejected if they have fewer frames than the number of emittingstates in the HMM. Setting this switch disables this reject mechanism 13 .-u flags By default, HRest updates all of the HMM parameters, that is, means, variances,mixture weights and transition probabilities. This option causes just the parameters indicatedby the flags argument to be updated, this argument is a string containing one or more ofthe letters m (mean), v (variance), t (transition) and w (mixture weight). The presence of aletter enables the updating of the corresponding parameter set.13 Using this option only makes sense if the HMM has skip transitions

17.17 HRest 278-v f This sets the minimum variance (i.e. diagonal element of the covariance matrix) to the realvalue f. This is ignored if an explicit variance floor macro is defined. The default value is 0.0.-w f Any mixture weight or discrete observation probability which falls below the global constantMINMIX is treated as being zero. When this parameter is set, all mixture weights are flooredto f * MINMIX.-B Output HMM definition files in binary format.-F fmt Set the source data format to fmt.-G fmt Set the label file format to fmt.-H mmf Load HMM macro model file mmf. This option may be repeated to load multiple MMFs.-I mlf This loads the master label file mlf. This option may be repeated to load several MLFs.-L dir Search directory dir for label files (default is to search current directory).-M dir Store output HMM macro model files in the directory dir. If this option is not given, thenew HMM definition will overwrite the existing one.-X ext Set label file extension to ext (default is lab).HRest also supports the standard options -A, -C, -D, -S, -T, and -V as described in section 4.4.17.17.3 TracingHRest supports the following trace options where each trace flag is given using an octal base000001 basic progress reporting.000002 output information on the training data loaded.000004 the observation probabilities.000010 the alpha matrices.000020 the beta matrices.000040 the occupation counters.000100 the transition counters.000200 the mean counters.000400 the variance counters.001000 the mixture weight counters.002000 the re-estimated transition matrix.004000 the re-estimated mixture weights.010000 the re-estimated means.020000 the re-estimated variances.Trace flags are set using the -T option or the TRACE configuration variable.

17.17 HRest 278-v f This sets the minimum variance (i.e. diagonal element of the covariance matrix) to the realvalue f. This is ignored if an explicit variance floor macro is defined. <strong>The</strong> default value is 0.0.-w f Any mixture weight or discrete observation probability which falls below the global constantMINMIX is treated as being zero. When this parameter is set, all mixture weights are flooredto f * MINMIX.-B Output HMM definition files in binary format.-F fmt Set the source data format to fmt.-G fmt Set the label file format to fmt.-H mmf Load HMM macro model file mmf. This option may be repeated to load multiple MMFs.-I mlf This loads the master label file mlf. This option may be repeated to load several MLFs.-L dir Search directory dir for label files (default is to search current directory).-M dir Store output HMM macro model files in the directory dir. If this option is not given, thenew HMM definition will overwrite the existing one.-X ext Set label file extension to ext (default is lab).HRest also supports the standard options -A, -C, -D, -S, -T, and -V as described in section 4.4.17.17.3 TracingHRest supports the following trace options where each trace flag is given using an octal base000001 basic progress reporting.000002 output information on the training data loaded.000004 the observation probabilities.000010 the alpha matrices.000020 the beta matrices.000040 the occupation counters.000100 the transition counters.000200 the mean counters.000400 the variance counters.001000 the mixture weight counters.002000 the re-estimated transition matrix.004000 the re-estimated mixture weights.010000 the re-estimated means.020000 the re-estimated variances.Trace flags are set using the -T option or the TRACE configuration variable.

logo

products

Resources

Company

Terms of service
Privacy policy
Cookie policy
Cookie settings
Imprint
Change language
Made with love in Switzerland
© 2024 Yumpu.com all rights reserved

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!