Addressing Representation Collapse in Vector Quantized Models with One Linear Layer

Vector Quantization (VQ) is essential for discretizing continuous representations in unsupervised learning but suffers from representation collapse, causing low codebook utilization and limiting scalability. Existing solutions often rely on complex optimizations or reduce latent dimensionality, which compromises model capacity and fails to fully solve the problem. We identify the root cause as disjoint codebook optimization, where only a few code vectors are updated via gradient descent. To fix this, we propose $\mathbf{\text{Sim}}$ple$\mathbf{\text{VQ}}$, which reparameterizes code vectors through a learnable linear transformation layer over a latent basis, optimizing the $\mathit{\text{entire}}\mathit{\text{linear}}\mathit{\text{space}}$ rather than nearest $\mathit{\text{individual}}\mathit{\text{code}}\mathit{\text{vectors}}$. Although the multiplication of two linear matrices is equivalent to applying a single linear layer, this simple approach effectively prevents collapse. Extensive experiments on image and audio tasks demonstrate that SimVQ improves codebook usage, is easy to implement, and generalizes well across modalities and architectures. The code is available at https://github.com/youngsheen/SimVQ.