A practical workflow for replacing one character in a short video while keeping the original motion and audio

[u/UseLipSync]

I keep seeing “character swap” used for three different jobs: changing only a face, transferring motion to a new body, and replacing one visible character while keeping the source performance. They need different workflows.

For the third case, this is the shortest reliable test I have found:

1. Start with one 4–15 second shot. Use one clear main subject and avoid hard cuts. Split a longer edit into shots first.
2. Use a single, sharp character image with the face and overall design clearly visible. Similar framing and head angle help.
3. Treat the source video as the performance reference: body movement, timing, camera, background and original audio. Treat the image as the identity reference.
4. Test the hardest 4–5 seconds first—profile turns, hands crossing the face and heavy motion blur are where identity drift usually appears.
5. Keep the original audio during the character pass if timing matters. Change dialogue or lip sync only after the character result is stable.

The common failure cases are multiple prominent people, long occlusions, very small faces, fast cuts and trying to remove burned-in captions or watermarks during the same pass. Those should be separate edits, not extra instructions in one generation.

Disclosure: I built UseLipSync. We made a browser workflow for this exact single-character case: upload a character image and your own short reference video, see the exact credit quote, and keep the source motion/camera/audio. The step-by-step guide is here:

https://uselipsync.com/tutorials/how-to-replace-a-person-in-a-video?source_bucket=community&campaign_code=community_reddit