You can choose this command after selecting two objects with cepstral coefficients (two MFCC's or LFCC's). With this command you perform dynamic time warping.

Algorithm

First we calculate the distance matrix D of all the distances between the cepstral frames of the two objects. This matrix has n₁ rows, the number of frames in the first object, and n₂ columns, the number of frames in the second object.

The elements of D are the distances d_ij between frame i (from the first object) and frame j (from the second one). The d_ij are composed of three parts:

where w₁, w₂ and w₃ are user-supplied weights and

d₁ = ∑^N_k=1 (c_ik - c_jk)²),

the sum of the squared distances between the N cepstral coefficients of the two frames.

d₂ = (c_i0 - c_j0)²

the difference between the average 'power' of the two frames.

d₃ = ∑^N_k=1 (r_ik - r_jk)²),

in which r_ik is the regression coefficient of the cepstral coefficient k, calculated from the frames within a time span of T seconds, the regression window length, around the centre of frame i.

After calculation of all the frame distances d_ij, we find the optimal path through the distance matrix D with a Viterbi-algorithm.

Links to this page

• DTW