Title: Self-Guidance: Training VQ-VAE Decoders to be Robust to Quantization Artifacts for High-Fidelity Neural Speech Codec
Primary area: applications to computer vision, audio, language, and other modalities
Keywords: neural speech codec, VQ-VAE, speech large language models

Abstract: Neural speech codecs, predominantly based on Vector-Quantized Variational Autoencoders (VQ-VAEs), serve as fundamental audio tokenizers for speech large language models (SLLMs). However, their reconstruction fidelity is limited by quantization errors introduced during latent space discretization. Existing solutions typically increase model complexity through larger codebooks or hierarchical quantization, which subsequently intensify the modeling challenge for downstream SLLMs. Inspired by the key insight that the codec decoder produces superior output from continuous pre-quantize embeddings, we propose a novel self-guided training mechanism that addresses this problem by enhancing decoder robustness rather than modifying the quantization process. Our method introduces an additional training objective that aligns the decoder's intermediate features when processing both quantized tokens and continuous pre-quantized embeddings through a feature-mapping loss. Extensive experiments on XCodec2 demonstrate that self-guidance consistently improves reconstruction quality across various codebook sizes and quantization techniques (FSQ, SimVQ), achieving state-of-the-art performance for low-bitrate speech codecs. The method requires minimal additional training cost and no inference-time modifications, offering an efficient solution for high-fidelity neural audio coding. Remarkably, our approach enables a 4× reduction in codebook size while maintaining comparable fidelity. Downstream text-to-speech experiments confirm that this reduction significantly improves LLM-based synthesis performance by simplifying the token modeling space.

TL;DR: We train neural speech codecs to be robust to compression artifacts by having the decoder learn to mimic its own high-quality output from uncompressed features, enabling better quality with smaller codebooks.