DEV Community 1h ago

I've Been Trying to Write AI Video Prompts for Months. They All Sucked Until I Found a Formula.

The Problem Nobody Talks About

Everyone's posting AI-generated videos - characters speaking with lip-sync, manga panels coming alive, virtual idols dancing. The pitch: "just describe what you want." I tried. For months. Here's what I got:

Character's face morphed by frame 2
"Slowly looks up" became "violent head shake"
Voice-over sounded like Google Translate
Same prompt, 3 runs, 3 completely different results
No idea what to include or how long the prompt should be

Tutorials were either too vague ("be detailed") or too technical (parameter tuning from line 1). The real issue: video prompts are structurally different from text/image prompts. You need to simultaneously control visuals, motion, audio, camera, and consistency constraints - in the right order, at the right length.

What I Found

A Skill in the Model Studio official repo called happyhorse-prompt-studio. It doesn't teach you theory - it asks you questions and assembles the prompt for you.

4-Phase Flow

1. Inspiration Menu
Shows you 4 "flavors" of what HappyHorse can do:

Flavor	What it does
A · Voiced Manga Drama	Characters talk to each other, with voice + lip-sync
B · Character Voice PV	Single character self-introduction, 8-10 sec
C · Manga Panel Motion	Static manga panel starts breathing
D · Virtual Idol MV	Idol performance with choreography

2. Discovery
Asks you conversationally: character appearance, scene, emotion, dialogue, voice type, art style, camera.

3. Prompt Assembly
Assembles using the HappyHorse Formula: Scene + Subject + Motion + Audio + Quality

Key techniques:

@「Image n」 syntax locks character identity across shots
Dialogue ≤15 characters (split shots if longer)
Japanese prompts work best (HappyHorse is JP-optimized)
Always end with キャラの顔・髪・衣装が変わらない (face/hair/outfit stays unchanged)

4. Quality Check
Auto-reviews: completeness, compliance, cost estimate, optimization tips.

Before vs. After

Dimension	Writing myself	With Prompt Studio
Attempts needed	10-20 before one usable	2-3 to satisfaction
Time per prompt	1-2 hours (research + trial)	5-10 minutes
Character consistency	Collapsed by frame 2	R2V syntax locks it
Common pitfalls	Learned by failing	Built-in troubleshooting

Honest Limitations

No guarantee of perfection on first try (AI video has inherent randomness)
Can't replace your creativity (character design is still yours)
Max ~30 seconds per generation
Requires API key (free tier available)
Japanese prompts get best results; CN/EN work but JP is optimized

Setup

npx skills add modelstudioai/skills --skill happyhorse-prompt-studio -g

Then tell your AI assistant: "I want to make a video with HappyHorse"

Execute the assembled prompt:

bl video generate --image ./char.png --prompt "[assembled prompt]" --download output.mp4