ControlVC: Zero-Shot Voice Conversion with Time-Varying Controls on Pitch and Speed

TL;DR

ControlVC is a neural voice conversion system that enables time-varying control over pitch and speed, improving speech quality and controllability in zero-shot, non-parallel scenarios.

Contribution

It introduces the first neural VC system with interpretable, time-varying control over pitch and speed using pre-trained encoders and a vocoder.

Findings

Outperforms baselines in speech quality

Successfully achieves time-varying pitch control

Effective in zero-shot, non-parallel conversion

Abstract

Recent developments in neural speech synthesis and vocoding have sparked a renewed interest in voice conversion (VC). Beyond timbre transfer, achieving controllability on para-linguistic parameters such as pitch and Speed is critical in deploying VC systems in many application scenarios. Existing studies, however, either only provide utterance-level global control or lack interpretability on the controls. In this paper, we propose ControlVC, the first neural voice conversion system that achieves time-varying controls on pitch and speed. ControlVC uses pre-trained encoders to compute pitch and linguistic embeddings from the source utterance and speaker embeddings from the target utterance. These embeddings are then concatenated and converted to speech using a vocoder. It achieves speed control through TD-PSOLA pre-processing on the source utterance, and achieves pitch control by manipulating the pitch contour before feeding it to the pitch encoder. Systematic subjective and objective evaluations are conducted to assess the speech quality and controllability. Results show that, on non-parallel and zero-shot conversion tasks, ControlVC significantly outperforms two other self-constructed baselines on speech quality, and it can successfully achieve time-varying pitch and speed control.