What is the behaviour of the preemphasis (preemph) parameter in python_speech_features MFCC?

[joelle-o-world]

python function, fbank, shows that preemphasis is applied before the signal is divided into frames.

[joelle-o-world]

def preemphasis(signal, coeff=0.95):
    """perform preemphasis on the input signal.
    :param signal: The signal to filter.
    :param coeff: The preemphasis coefficient. 0 is no filter, default is 0.95.
    :returns: the filtered signal.
    """
    return numpy.append(signal[0], signal[1:] - coeff * signal[:-1])

[joelle-o-world]

js translation:

function preemphasis(signal, coeff=0.95){
   let arr = [signal[0]];
   for(let i=1; i<signal.length; ++i)
      arr.push( signal[i] - coeff * signal[i-1] );

   return arr
}

[joelle-o-world]

Tentatively closing this issue having added a Preemphasis transform stream....