Pseudo-Cepstrum: Pitch Modification for Mel-based Neural Vocoders

Nikolaos Ellinas, Alexandra Vioni, Panos Kakoulidis, Georgios Vamvoukakis, Myrsini Christidou, Konstantinos Markopoulos, Junkwang Oh, Gunu Jho, Inchul Hwang, Aimilios Chalamandaris and Pirros Tsiakoulis

Abstract: This paper introduces a cepstrum-based pitch modification method that can be applied to any mel-spectrogram representation. As a result, this method is compatible with any mel-based vocoder without requiring any additional training or changes to the model. This is achieved by directly modifying the cepstrum feature space in order to shift the harmonic structure to the desired target. The spectrogram magnitude is computed via the pseudo-inverse mel transform, then converted to the cepstrum by applying DCT. In this domain, the cepstral peak is shifted without having to estimate its position and the modified mel is recomputed by applying IDCT and mel-filterbank. These pitch-shifted mel-spectrogram features can be converted to speech with any compatible vocoder. The proposed method is validated experimentally with objective and subjective metrics on various state-of-the-art neural vocoders as well as in comparison with traditional pitch modification methods.

Pseudo-Cepstrum method

Pseudo-Cepstrum Cepstrum example

Pitch modification in semitone steps

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Otherwise he would have been stripped of his clothes. End quote.
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Upon the 29th July the same year,
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John Williams, a young fellow only twenty-three years of age, awaited execution in 1827 for stealing in a dwelling-house.
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Wash out the bowl with a little lukewarm water and add this to the dough. If it should prove too soft, work in, cautiously, a little more flour.
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Working through vast agencies of commerce and employing great masses of men in movements of production
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And every day that passes offers more chances to work for those who want to work.
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Enclosing and protecting the nervous centers (cerebrospinal axis).
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Most remarkable of all the principles which have been discovered by embryologists is the "Recapitulation Doctrine"
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And decorated here and there with large reliefs representing bulls and lions and dragons,
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And no written description of the role the local police were expected to perform.
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