Frankly, both papers you linked give no justification for using the mel filterbank instead of any other filtering/frequency reduction before doing the IDCT to g

Frankly, both papers you linked give no justification for using the mel filterbank instead of any other filtering/frequency reduction before doing the IDCT to get the cepstrum. This is what I mean! Why take a filterbank designed for audio and apply it to images except to use the buzzwords? In any case, at least I know it is used by researchers (even if I don't agree with the why). Thanks!