I am working on a speech synthesis model and I am looking to evaluate my synthesized speech. I found that most people use the Mel Cepstral Distortion (MCD) which can be calculated by the formula:
I have ground-truth speech and the synthesised version so I calculate the MFCCs for both (taking 25 coefficients) and then apply the formula. The result I get is around 300, which seems orders of magnitude larger than what I should get. I tried doing cepstral mean normalization which brings the number down to around 30 but I notice that most of the time this number is <10. The speech I synthesize is not so bad so I must be doing something wrong. Does anyone have any ideas?
P.S. The way I produce the speech ensures that it be aligned with the original(more or less). I wonder if a slight misalignment could cause this issue and if so should I use DTW to align the audios?
Edit Also If anyone knows of a library that calculated MCD when given an audio file then I could use that to compare my results.