MiniMaxH3_LatentUpscaler

ComfyUI custom node for latent spatial upscaling between MiniMax H3 samplers.

Not a learned AI upscaler. Stock LatentUpscaleBy / AddNoise break on MiniMax’s ComfyUI NestedTensor AV latents (video [B,24,T,H/16,W/16] + audio [B,32,2,T_audio]).

MiniMax H3 Latent Upscale Combined (latent/minimax_h3)

Required inputs: LATENT, scale_by, method, MODEL, NOISE, SIGMAS
Optional inputs: positive, negative (CONDITIONING)
Outputs: latent, positive, negative

Does:

1. Upscale NestedTensor video H,W via F.interpolate (audio tensor passed through)
2. Re-noise video at sigmas[0] (noise_scaling + inverse_noise_scaling)
3. audio_denoise (0–1): how much to re-noise audio for pass 2
   • 0 = lock pass-1 audio
   • 1 = full remix so sampler 2 can improve audio
   • 0.25–0.5 = light polish
4. If CONDITIONING is connected: spatially upscale minimax_refs / minimax_keyframes visual latents and sync latent_h / latent_w
5. Park LATENT on CPU + soft_empty_cache (no model unload)

1. SamplerCustomAdvanced #1 → high/majority σ at low res
2. Take denoised_output
3. MiniMax H3 Latent Upscale Combined
   • latent = denoised_output
   • positive/negative = same cond used for pass 1
   • RandomNoise + low sigmas + model
   • audio_denoise = 1.0 (or 0.35 for gentler audio edits)
4. Build a new Guider from Combined’s returned positive / negative
5. SamplerCustomAdvanced #2 — DisableNoise + low sigmas + Combined latent + new Guider

If audio garbles with audio_denoise>0, run more of the schedule in pass 1 (audio settles late) or lower audio_denoise.

minimax_refs packs each ref with its own latent + latent_h/latent_w. After the target canvas grows 2×, refs sized for the 0.5MP “match” canvas sit at the wrong relative scale and RoPE row layout vs the new target — classic identity warp. Combined doubles ref visual latents and metadata together.

Avoid Easy-Use Empty Cache / force-unload between passes (especially with --disable-dynamic-vram + quantized MiniMax + SageAttention).

ComfyUI/custom_nodes/MiniMaxH3_LatentUpscaler/ — restart or reload custom nodes.