Video Background Replacement Workflow & Testing

Need background replacing workflow and example video processing. ATTENTION: Bidding is 50(!) usd MAX. You will need to do manual testing and processing, so Claude/GPT instructions copy-paste will not work at all, you will just waste your time and receive extra bad rating if no processing results will be present. I already have partial workflow which needs some enhancements. Details and test video will be shared in the chat. Basically it consists of: 0) “ffmpeg -i input.mp4 -q:v 2 01_%04d.jpg” 1) batch_mask_generation which automates birefnet_mask_workflow and produces masks files of video characters
2) batch_background_removal which produces cutout files 3) background generation (will be discussed) and merging with background video ffmpeg -i “back2x.mp4” -framerate 60 -i “cutout_%05d_.png” -filter_complex “[1:v]format=rgba[char];[0:v][char]overlay=0:0:shortest=1” -c:v libx264 -pix_fmt yuv420p output.mp4 4) put frames back to mp4:
ffmpeg -i cutout\filled\cutout_%05d_.png -c:v libx264 -pix_fmt yuv420p output.mp4