arXiv:2604.20902cs.LGcs.AI2026-04

用轻量波浪包变换引导图像生成,先粗后细提升质量

Frequency-Forcing: From Scaling-as-Time to Soft Frequency Guidance

  • 用自学习的低频信号软性引导像素生成顺序
  • 在ImageNet-256上显著优于主流像素与潜在空间基线
  • 无需预训练编码器,适配数据分布且可融合语义流

标准流匹配模型均匀传输噪声,而显式建立粗略到精细的生成顺序对合成自然图像极为有效。两种近期方法提供不同范式:K-Flow通过将频率缩放变量重解为流时间,以硬性频率约束运行于变换幅度空间;Latent Forcing则通过异步时间调度耦合像素流与辅助语义潜流,实现软性排序,保持像素插值路径不变。我们观察到,通过早期成熟辅助流引导生成,是一种兼容性强、无需重写核心流坐标的尺度有序生成路径。基于此,提出Frequency-Forcing,以软机制实现K-Flow的频率排序:标准像素流由更早成熟的辅助低频流引导。不同于依赖重型预训练编码器(如DINO)的原始潜流,我们的频率‘草稿’来自数据本身的轻量可学习小波包变换,称为自强迫信号。该信号避免外部依赖,且学习到的基底比固定基更适应数据统计。在ImageNet-256上,Frequency-Forcing持续优于强像素与潜空间基线,并可自然与语义流结合获得进一步增益,表明基于强迫的尺度排序是硬频率流的通用、路径保留型替代方案。

原文摘要 · Abstract (English)

While standard flow-matching models transport noise to data uniformly, incorporating an explicit generation order - specifically, establishing coarse, low-frequency structure before fine detail - has proven highly effective for synthesizing natural images. Two recent works offer distinct paradigms for this. K-Flow imposes a hard frequency constraint by reinterpreting a frequency scaling variable as flow time, running the trajectory inside a transformed amplitude space. Latent Forcing provides a soft ordering mechanism by coupling the pixel flow with an auxiliary semantic latent flow via asynchronous time schedules, leaving the pixel interpolation path itself untouched. Viewed from the angle of improving pixel generation, we observe that forcing - guiding generation with an earlier-maturing auxiliary stream - offers a highly compatible route to scale-ordered generation without rewriting the core flow coordinate. Building on this, we propose Frequency-Forcing, which realizes K-Flow's frequency ordering through Latent Forcing's soft mechanism: a standard pixel flow is guided by an auxiliary low-frequency stream that matures earlier in time. Unlike Latent Forcing, whose scratchpad relies on a heavy pretrained encoder (e.g., DINO), our frequency scratchpad is derived from the data itself via a lightweight learnable wavelet packet transform. We term this a self-forcing signal, which avoids external dependencies while learning a basis better adapted to data statistics than the fixed bases used in hard frequency flows. On ImageNet-256, Frequency-Forcing consistently improves FID over strong pixel- and latent-space baselines, and naturally composes with a semantic stream to yield further gains. This illustrates that forcing-based scale ordering is a versatile, path-preserving alternative to hard frequency flows.

图像生成流匹配频率引导自强迫

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