Hi V2EX,
If you have scrolled TikTok or Reels this October, you have probably seen the Bulin 47 freestyle: Dominican dembow artist Bulin 47 gets stopped outside a venue in Madrid by creator Kevin Wai, who holds up a portable speaker, and he drops an improvised freestyle on the spot. Within days people started remixing it with AI — same scene, same crowd, same beat, but a different person in the lead.
I built a small web tool for exactly that:
Bulin 47 AI — https://bulin47ai-video.com
Upload one photo → get the original Bulin 47 freestyle with you as the lead performer. No prompt, no editing, no app.
Under the hood it uses a video-edit model with the original clip as the reference, so the venue, the red-lit staircase, the speaker holder, the crowd reactions, the camera moves and the beat all stay the same — only the performer is swapped for the person in your photo.
I looked at most of the Bulin 47 generators that popped up this month before building this. These are the things that bugged me as a user, and what I did instead:
1. 720P HD by default — not a 480P upsell Every video is 720P HD, 15 seconds, with the original sound. There is no cheap low-res tier that you only discover after paying. Faces and hand gestures hold up noticeably better at 720P, which matters for a clip where the whole point is that your friends recognise you.
2. Honest per-video pricing
One credit = one full 15-second 720P video. Some sites advertise a low "per clip" price that is actually calculated for a 5-second 480P clip, while the full-length video costs about three times as many credits — and their entry pack sometimes can't even make one full video. I didn't want to do that.
3. No subscription, credits never expire One-time payments through Stripe. Unused videos stay in your balance.
4. Automatic refunds If a render fails, times out, or is blocked by the model's safety filter, the video goes straight back to your balance. No support ticket.
5. You can close the tab Rendering takes a few minutes. Jobs keep running server-side, and a background job finishes or refunds them even if you leave — the result waits in "My Videos".
6. Friendly on mobile The whole flow works in a phone browser. Photos are resized in the browser before upload so it's fast on mobile data, and if you start before signing in, your photo and settings are kept through the Google sign-in.
7. Private by default Your photos and videos are visible only to you, are not used for ads, and you can delete them anytime.
8. English and Spanish The trend is huge in Latin America and Spain, so the whole site is also available in Spanish: https://bulin47ai-video.com/es/
Guides if you want the background on the trend:
Feedback is very welcome — especially on result quality and anything confusing in the flow. Thanks for reading!
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