ComfyUI-Cadence-Retime: Twixtor-Style Speed Ramps for MiniMax H3

Hud224 released ComfyUI-Cadence-Retime (GitHub), a ComfyUI node pack that analyzes uneven video cadence and applies variable, fractional frame remaps directly to an IMAGE batch. It brings Twixtor-style speed ramps and motion linearization into ComfyUI — no After Effects, no external video decoder, no CSV round trip.

The pack was built for MiniMax H3 workflows, where the model's baked-in speed ramps are a common complaint: H3 clips often start slow, speed up, then settle. Cadence Retime normalizes that motion into constant screen travel, or lets you draw your own speed curve over the shot.

The Cadence Retime nodes: motion analysis, map builders, and apply nodes under the Cadence: prefix.

What it does

• Linearize uneven motion — in-memory optical-flow analysis measures screen displacement from the loaded IMAGE batch and builds a monotonic, fractional source-frame map. gentle, standard and strong modes progressively approach constant screen travel.
• Build creative retimes — three map builders: Retime Preset (linear, ease-in/out, slow-middle), Source-Time Curve (direct output-time → source-time mapping), and Speed Curve (editable 0.25×–4× playback-speed graph, logarithmic scale).
• Sample exact frames — whole-frame positions always come from the untouched source batch; only fractional positions sample an optional dense RIFE/GMFSS interpolation batch, so unretimed frames stay sharp.
• Keep audio synchronized — Cadence: Apply Retime + Audio retimes the audio track with the same picture map using synchronized varispeed (pitch follows speed), or passes audio through untouched.
• Import legacy frame maps — text, JSON, CSV content, local CSV paths, or a direct CADENCE_MAP connection.

The interactive speed-curve editor: above the center line plays faster, below plays slower.

Recommended workflow

For a typical H3 clip, the compact Normalize Motion node is the fastest path:

1. Load the untouched video as an IMAGE batch and connect it to source_images.
2. Optionally run the same source through RIFE or GMFSS at ×4 and connect it to motion_interpolated_images.
3. Send retimed_images to Video Combine, wiring output_fps to its frame-rate input.

Recommended first-pass settings: strength: standard, analysis_resolution: 256, minimum_static_frames: 3, motion_multiplier: 0 (automatic) or 4 with an explicit ×4 VFI branch. ×4 interpolation is the normal working setting; ×8 only for difficult parallax or large corrections. protect_static_edges stays off for full-move linearization, and can be enabled to preserve an intentional static start or end settle.

Context

The daily summary on the Banodoco Discord featured the release on August 21 (announcement): run a ×4 interpolation pass, then the node pulls fractional frames on demand and refreshes in about a second — matching the "render small, retime later" style huddadudd uses in After Effects, now inside ComfyUI.

Installation

Clone into ComfyUI/custom_nodes/ and restart ComfyUI; no extra Python packages are required. The nodes appear under the Cadence Retime menu with Analysis, Maps and Apply subcategories, and a test suite ships with the repo (python -m unittest discover -s tests).