arXiv:2601.17124cs.CV2026-01被引 5

仅改一行代码,让图像生成的离散量化更高效。

iFSQ: Improving FSQ for Image Generation with 1 Line of Code

  • 用分布匹配映射替换原激活函数,解决量化崩溃问题。
  • 4比特/维度是离散与连续表示的最佳平衡点。
  • 验证了自回归模型收敛快但上限低,适合快速生成场景。

当前图像生成领域分为基于离散标记的自回归模型和基于连续潜在变量的扩散模型,二者分立源于VQ-VAE与VAE的差异,阻碍了统一建模与公平比较。有限标量量化(FSQ)理论上可弥合此鸿沟,但原始FSQ因等间隔量化导致激活崩溃,造成重建保真度与信息效率的权衡。本文提出iFSQ,仅通过将原FSQ中的激活函数替换为分布匹配映射,即可在数学上保证最优区间利用率与重建精度。该方法仅需一行代码,且作为可控基准,揭示两个关键发现:(1) 离散与连续表示的理想平衡点约为4比特/维度;(2) 在相同重建约束下,自回归模型初始收敛更快,而扩散模型达到更高性能上限,暗示严格序列依赖可能限制生成质量上限。最后,将表示对齐(REPA)引入自回归模型,构建LlamaGen-REPA。代码已开源。

原文摘要 · Abstract (English)

The field of image generation is currently bifurcated into autoregressive (AR) models operating on discrete tokens and diffusion models utilizing continuous latents. This divide, rooted in the distinction between VQ-VAEs and VAEs, hinders unified modeling and fair benchmarking. Finite Scalar Quantization (FSQ) offers a theoretical bridge, yet vanilla FSQ suffers from a critical flaw: its equal-interval quantization can cause activation collapse. This mismatch forces a trade-off between reconstruction fidelity and information efficiency. In this work, we resolve this dilemma by simply replacing the activation function in original FSQ with a distribution-matching mapping to enforce a uniform prior. Termed iFSQ, this simple strategy requires just one line of code yet mathematically guarantees both optimal bin utilization and reconstruction precision. Leveraging iFSQ as a controlled benchmark, we uncover two key insights: (1) The optimal equilibrium between discrete and continuous representations lies at approximately 4 bits per dimension. (2) Under identical reconstruction constraints, AR models exhibit rapid initial convergence, whereas diffusion models achieve a superior performance ceiling, suggesting that strict sequential ordering may limit the upper bounds of generation quality. Finally, we extend our analysis by adapting Representation Alignment (REPA) to AR models, yielding LlamaGen-REPA. Codes is available at https://github.com/Tencent-Hunyuan/iFSQ

图像生成量化自回归扩散模型

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