ComfyUI custom node for SPEED — Spectral Progressive Diffusion for faster sampling. Progressively expands the latent resolution during denoising, reducing computation while preserving visual quality.
Official code: https://github.com/howardhx/speed
Key references:
- Project page: https://howardxiao.ca/speed/
- Paper (PDF): https://howardxiao.ca/speed/paper/paper.pdf
- arXiv: https://arxiv.org/abs/2605.18736
Workflow:
| SPEED sampler (this node) | Baseline (euler sampler) |
|---|---|
mode=delta_optimal model_preset=flux scales=0.5,1.0 delta=0.01 transform=dct base_sampler=euler 20s 1.33x faster |
 26.5s 1.00x |
- Place this folder under your ComfyUI
custom_nodesdirectory, then restart ComfyUI. - Connect the Sampler SPEED (Spectral Progressive Diffusion) output to SamplerCustomAdvanced.
| Input | Type | Default | Description |
|---|---|---|---|
base_sampler |
combo | euler |
Underlying ODE solver. Any comfy.k_diffusion.sampling sampler supported. |
transform |
combo | dct |
Spectral basis for expansion: dct (any ratio), dwt (2× only), fft (any ratio). |
mode |
combo | delta_optimal |
delta_optimal computes transitions from the power-spectrum preset. manual uses user-specified sigma thresholds. |
model_preset |
combo | flux |
Power-spectrum preset: flux, wan21, or custom (use spectrum_A / spectrum_beta). |
scales |
string | 0.5,1.0 |
Comma-separated resolution fractions ending at 1.0. e.g. 0.25,0.5,1.0. |
delta |
float | 0.01 |
Noise-dominated tolerance (Eq. 9). Smaller values delay transitions. |
manual_sigmas |
string | 0.85 |
Comma-separated sigma thresholds (one per transition). Used in manual mode. |
spectrum_A |
float | 203.615 |
Power-law amplitude (used when model_preset=custom). |
spectrum_beta |
float | 1.915 |
Power-law decay exponent (used when model_preset=custom). |
seed |
int | 0 |
Seed for spectral-noise padding at each transition. |
Set model_preset to flux or wan21 and adjust scales and delta. Transition timing is computed automatically from the VAE power spectrum using Eq. 9 and Eq. 10 of the paper.
Set mode=manual and supply comma-separated sigma thresholds in manual_sigmas (one per transition between adjacent scales). Sigma decreases as denoising progresses, so the first threshold should be larger than the last (e.g. 0.95,0.85 for three scales).
This implementation is based on and derived from the official SPEED repository by Howard Xiao et al.:
- Official code: https://github.com/howardhx/speed (BSD 3-Clause)
- Paper: Xiao, H., Chao, B., Yariv, L., & Wetzstein, G. (2026). Spectral Progressive Diffusion for Efficient Image and Video Generation.
Please see the original project page and repository for full authorship, details, and license information.
@article{xiao2026spectral,
author = {Xiao, Howard and Chao, Brian and Yariv, Lior and Wetzstein, Gordon},
title = {Spectral Progressive Diffusion for Efficient Image and Video Generation},
year = {2026},
}