CASC-XVC: Zero-Shot Cross-Lingual Voice Conversion with Content Accordant and Speaker Contrastive Losses

Cross-lingual voice conversion (XVC) is a technology that modifies speaker identity while preserving linguistic content in scenarios where the source and target speakers use different languages. Previous non-parallel disentanglement-based methods face severe training-testing inconsistency issues in XVC tasks due to language mismatch and the lack of multilingual parallel data, which inevitably compromise the quality of the synthesized speech. In this paper, we propose CASC-XVC, a zero-shot XVC method incorporating with content accordant (CA) and speaker contrastive (SC) losses. Specifically, this method adopts the framework of FreeVC-s as the backbone. We design a cross-lingual fine-tuning process employing pairs of utterances from speakers in different languages to update the modules used in the inference stage. A CA loss and an SC loss are introduced to deal with the lack of true parallel targets in the fine-tuning process. Moreover, we use shared self-supervised learning (SSL) representations across different languages along with information perturbation for content disentanglement. Both subjective and objective results on a bilingual (English and Chinese) dataset demonstrate that our approach achieves significant improvements in XVC tasks.