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How to swap a cast member in an existing source video with Mini Max H3 Director Cut Studio

Replace a person in a source video shot by shot using the Character-Swap LoRA, the H3 Relay and SAM3.1 masks.

  • Content
  • Advanced
  • 4 hours
  • From the README
  • Any agent

Voice cloning. The swap replaces a real person's appearance in footage, so you need permission from the performer and the source video owner before using the output.

Who it is forA video editor or creator who has a source clip and needs to replace one actor with a reference image, and has the Character-Swap models installed.

The problemRe-shooting a scene to change one performer is costly, and simple masking leaves ghosting or edge artifacts when the new person has a different body or pose.

The outcomeA shot-level cast remake of the source video where the selected roles are swapped and the rest of the frame is kept, with dirty segments regenerated.

What you need first

  • A Windows PC with ComfyUI installed, plus a high-VRAM machine if you want to run the local server roles described in the README
  • Completed Step 1 deployment (Studio Runtime, Qwen3-TTS and VoxCPM2) from the README's step1.md
  • The model files listed in the README, saved under the exact file names it gives
  • Model and source-footage licenses checked by you; the README says weights are not included in the source code

Steps

  1. Install the akatz-ai/h3-relay custom node into ComfyUI/custom_nodes/h3-relay/ and place every Character-Swap model listed in the README, including sam3.1_multiplex_fp16.safetensors for multi-character swaps.
  2. Confirm ffmpeg and ffprobe run from the PATH on the server.
  3. Optionally run install_h3_cache_status_server.bat on the ComfyUI host to show cache, VRAM and GPU status in Studio and the Windows Tray. (inferred, check the README)
  4. Start the studio with .\run_h3_prompt_studio.bat, choose Source Video Cast Remake H3, and open the Shot Visual Editor.
  5. Check the roles to swap, choose a P Picture for each, leave other people on KEEP V1, click SAVE SHOT, then click REGENERATE DIRTY.

Prompt for your agent

Using the repo karuvanan/MiniMax-H3-Director-Cut-Studio, set up the Source Video Cast Remake H3 path for the source clip <source video path> and swap the role named <role name> with the reference image <P picture path>. Expected output: a regenerated shot in the studio with the swap applied to that role only. Verify that LabsH3PrepareVideo, H3RelayWindowedEdit, SAM3_VideoTrack and SAM3_TrackToMask appear in ComfyUI without IMPORT FAILED.

Caveat. The README lists many separate model files, a custom node and system ffmpeg that must all be in place before the Character-Swap path runs, and the source footage license must be checked separately.

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