Hidden Markov Models

Warning

Still under construction, I hope to fill these sections out as I have time.

Standard topology

Kaldi topology reference

See also

• https://kaldi-asr.org/doc/hmm.html

• https://kaldi-asr.org/doc/tree_internals.html

• https://kaldi-asr.org/doc/tree_externals.html

MFA topology

MFA uses a variable 5-state topology for modeling phones. Each state has a likelihood to transition to the final state in addition to the next state. What this is means is that each phone has a minimum duration of 10ms (corresponding to the default time step for MFCC generation), rather than 30ms for a more standard 3-state HMM. Having a shorter minimum duration reduces alignment errors from short or dropped phones, i.e., American English flaps or schwas, or accommodate for dictionary errors (though these should still be fixed).