Definition and construction of HMM model
Recognition of vowel sequence based on HMM - part II
Computation of emitted probabilities and passing likelihood
through whole HMM model
Tasks to do:
- Definition of HMM-model transient matrix, computation of emitted
probabilities in HMM states
- Determine parameters of HMM transient matrix for the
supposed utterance in the following form - duration of each
vowel same as separation pause is 1s. Save parameters into the
structure variable hmm.a in the related HMM
model. Order of the matrix A
should be hmm.states+1, i.e. it is necessary to take
into the account also the leaving of the last HMM state.
- Compute the matrix of all emitted log-probabilities (with
suitable thresholding) for all states of given HMM model. This
matrix should have the number of rows related to the number of
states in HMM model and number of columns related to the number of
feature vectors (short-time frames) in analyzed utterance.
- 1st checked result (1 point): Display for
the utternaces P0, P1
- Computed emitted log-probabilities for all states (use
function pcolor followed by shading interp).
- Display in command prompt (or variable space) matrix of
transient probabilities A.
- Computation of likelihood of passing through HMM using Viterbi algorithm
- Create function myviterbi for the computation of likelihood
of passing through HMM model based on Viterbi algorithm. Input of
this function should be matrix of feature vectors (cepstra) and
chosen HMM model. Output should be the final likelihood of passing
through HMM model.
- Determine optimum path using backtracing of passing through HMM model.
- Determine boundaries of particular vowels in utterances P0, P1
- 2nd checked result (1 point): Display for
test utterances P0, P1
- Likelihoods of passing through HMM model AEIOU for these 3
possible sequences, i.e. AEIOU, UOIEA, IUAOE.
- Display also the line representing the optimum path into the
plot with emitted probabilities in all states
(previous checked result).
- Waveform and spectrogram with determined phone boudaries for
correct utterance P0.
- On the bsais of known boundaries, precise transient matrix A and
compute on more time likelihoods of passing through HMM model with
corrected transient probabilities.