AnyFlow让视频生成模型任意步数都能稳定高效,突破了传统方法的性能瓶颈。
AnyFlow: Any-Step Video Diffusion Model with On-Policy Flow Map Distillation

- 通过学习任意时间间隔的流图转移,替代固定步数的终点对齐。
- 在1.3B到14B参数模型上,少步生成性能超越或持平现有方法,且支持多步扩展。
- 适用于需要灵活采样步数的视频生成场景,尤其适合大模型部署。
少步视频生成已因一致性蒸馏取得显著进展。然而,一致性蒸馏模型在测试时增加采样步数后性能常下降,限制了其在任意步视频扩散中的应用。这源于一致性蒸馏将原概率流ODE轨迹替换为一致性采样轨迹,削弱了ODE采样在测试时的可扩展性。为此,我们提出AnyFlow,首个基于流图的任意步视频扩散蒸馏框架。不同于仅针对少数固定步数的蒸馏,AnyFlow优化完整的ODE采样轨迹。我们将其蒸馏目标从端点一致性映射(zₜ→z₀)转为任意时间区间内的流图转移学习(zₜ→zᵣ)。进一步提出流图反向模拟,将完整欧拉滚动分解为快捷流图转移,实现高效的在线策略蒸馏,降低测试时误差(即少步采样的离散化误差与因果生成中的暴露偏差)。在双向与因果架构上,覆盖1.3B至14B参数规模的大量实验表明,AnyFlow在少步条件下性能达到或超越现有基于一致性的方法,同时具备随采样步数预算增长而提升的能力。
原文摘要 · Abstract (English)
Few-step video generation has been significantly advanced by consistency distillation. However, the performance of consistency-distilled models often degrades as more sampling steps are allocated at test time, limiting their effectiveness for any-step video diffusion. This limitation arises because consistency distillation replaces the original probability-flow ODE trajectory with a consistency-sampling trajectory, weakening the desirable test-time scaling behavior of ODE sampling. To address this limitation, we introduce AnyFlow, the first any-step video diffusion distillation framework based on flow maps. Instead of distilling a model for only a few fixed sampling steps, AnyFlow optimizes the full ODE sampling trajectory. To this end, we shift the distillation target from endpoint consistency mapping $(z_{t}\rightarrow z_{0})$ to flow-map transition learning $(z_{t}\rightarrow z_{r})$ over arbitrary time intervals. We further propose Flow Map Backward Simulation, which decomposes a full Euler rollout into shortcut flow-map transitions, enabling efficient on-policy distillation that reduces test-time errors (i.e., discretization error in few-step sampling and exposure bias in causal generation). Extensive experiments across both bidirectional and causal architectures, at scales ranging from 1.3B to 14B parameters, demonstrate that AnyFlow achieves performance matches or surpasses consistency-based counterparts in the few-step regime, while scaling with sampling step budgets.
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