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The paper introduces HoliTok, a continuous speech tokenizer that encodes 48kHz speech into a compact 25Hz sequence of 128-dimensional latents. HoliTok is trained with a progressive strategy to jointly preserve signal fidelity, incorporate semantic information, and maintain latent learnability. Experiments using a unified AR+DiT model demonstrate that HoliTok achieves competitive reconstruction fidelity and robust performance in both speech synthesis and recognition tasks without additional optimization tricks, suggesting its effectiveness as a foundational representation for unified spoken language modeling.
Finally, a speech tokenizer that doesn't require extra optimization tricks to work robustly for both generation and understanding tasks in a unified architecture.
Unified speech foundation models require a holistic tokenization space that is both learnable by language models and decodable into high-quality waveforms. Existing speech tokenizers, however, often fail to satisfy these requirements simultaneously, leading to increased architectural complexity and more involved training designs. We propose HoliTok, a continuous Holistic speech Tokenization model designed for unified generation-understanding modeling. HoliTok encodes 48~kHz speech into a compact 25~Hz sequence of 128-dimensional latents. It is trained with a progressive strategy that jointly preserves signal-level fidelity, incorporates semantic information, and maintains strong latent learnability. Based on this tokenization, we build a unified AR+DiT model for speech synthesis and recognition, where the same latent sequence supports both generation-specific and unified generation-understanding tasks. Experiments show that HoliTok achieves competitive reconstruction fidelity, improves generative learnability for high-quality and controllable synthesis, and, among the evaluated representations, is the only one that operates robustly in our unified generation-understanding architecture without additional optimization tricks. These results suggest that HoliTok serves as an effective speech tokenizer and a foundational representation interface for unified spoken language modeling. The code is available at: https://github.com/bovod-sjtu/HoliTok.