---
title: Video Replace Background
emoji: 🎬
colorFrom: indigo
colorTo: green
sdk: gradio
sdk_version: 6.29.1
app_file: app.py
pinned: false
short_description: replace video background with LTX alpha LoRA + H3 inpainting
suggested_hardware: zero-a10g
---

# Subject on a New Background

Put a video subject on a new, generated background, by chaining two models:

1. **Lift the subject** with the LTX-2.5 Alpha-Gen matte LoRA (`hugging-apps/ltx-2-5-alpha-matte`), called over the
   gradio API: video in, alpha matte + green-screen out.
2. **Regenerate the background** with MiniMax-H3 ref2va inpainting, held in this Space. The subject is handed to H3
   as conditioning; the inverted matte marks the background as the region to repaint. Text encoding runs on the
   `qwen3vl-conditioner` Space, so this one never loads a 60 GiB encoder.

Upload a clip, describe the background, and press **Replace background** - or click one of the examples. **Relight
strength** is the quality lever: at 0 the subject is held exactly (best when the new background's light matches the
original); turn it up and H3 lights the subject into the new scene so it does not read as a cutout, while keeping
identity.

Runs on ZeroGPU with the ref2v turbo LoRA at 8 steps. The matte and conditioner calls bill the caller's ZeroGPU
quota, same as the denoise.