app.py

"""
Visual Chronometer + NexaAPI: AI Video Generation Demo
Based on arXiv:2603.14375

HuggingFace Space: visual-chronometer-via-nexaapi
"""

import gradio as gr
import os
import requests
from nexaapi import NexaAPI

# Initialize NexaAPI client
# Get your API key at: https://nexa-api.com or https://rapidapi.com/user/nexaquency
client = NexaAPI(api_key=os.environ.get('NEXA_API_KEY', ''))

AVAILABLE_MODELS = [
    'veo-3',
    'kling-v3-pro',
    'sora',
    'wan',
]

# Example prompts inspired by Visual Chronometer paper's test cases
EXAMPLE_PROMPTS = [
    "A hummingbird hovering near a flower, natural wing speed, photorealistic",
    "A person walking naturally at normal speed through a park",
    "Water flowing over rocks in a stream, natural flow rate",
    "A cat jumping from a table to the floor, natural gravity",
    "A person falling onto a soft bed, natural gravity speed",
]


def generate_video(api_key: str, prompt: str, model: str, duration: int) -> tuple:
    """
    Generate a video using NexaAPI.
    
    Returns:
        (video_url, status_message)
    """
    if not api_key:
        return None, "❌ Please enter your NexaAPI key. Get one at https://nexa-api.com"
    
    if not prompt:
        return None, "❌ Please enter a prompt"
    
    try:
        # Use provided API key
        local_client = NexaAPI(api_key=api_key)
        
        result = local_client.generate(
            model=model,
            prompt=prompt,
            duration=duration,
            aspect_ratio='16:9',
        )
        
        status = f"""✅ Video generated successfully!
        
📹 Model: {model}
⏱️ Duration: {duration}s
💰 Estimated cost: ~$0.05

🔗 Links:
  • NexaAPI: https://nexa-api.com
  • RapidAPI: https://rapidapi.com/user/nexaquency
  • pip install nexaapi: https://pypi.org/project/nexaapi
  • Paper: https://huggingface.co/papers/2603.14375
        """
        
        return result.url, status
        
    except Exception as e:
        return None, f"❌ Error: {str(e)}\n\nGet your API key at: https://nexa-api.com"


# Build Gradio interface
with gr.Blocks(title="Visual Chronometer + NexaAPI") as demo:
    gr.Markdown("""
    # 🎬 Visual Chronometer + NexaAPI: AI Video Generation Demo
    
    Based on the research paper: **["The Pulse of Motion: Measuring Physical Frame Rate from Visual Dynamics"](https://huggingface.co/papers/2603.14375)** (arXiv:2603.14375)
    
    The paper reveals that AI video generators suffer from **"Chronometric Hallucination"** — physically incorrect motion speeds.
    This demo lets you generate videos via **[NexaAPI](https://nexa-api.com)** (50+ models, 5× cheaper than official pricing).
    """)
    
    with gr.Row():
        with gr.Column():
            api_key = gr.Textbox(
                label="NexaAPI Key",
                placeholder="Get your key at https://nexa-api.com or https://rapidapi.com/user/nexaquency",
                type="password"
            )
            prompt = gr.Textbox(
                label="Prompt",
                placeholder="Describe the video you want to generate...",
                lines=3
            )
            model = gr.Dropdown(
                label="Model",
                choices=AVAILABLE_MODELS,
                value='veo-3'
            )
            duration = gr.Slider(
                label="Duration (seconds)",
                minimum=3,
                maximum=10,
                value=5,
                step=1
            )
            generate_btn = gr.Button("🎬 Generate Video", variant="primary")
        
        with gr.Column():
            video_url = gr.Textbox(label="Generated Video URL")
            status = gr.Textbox(label="Status", lines=10)
    
    gr.Examples(
        examples=[[p] for p in EXAMPLE_PROMPTS],
        inputs=[prompt],
        label="Example Prompts (from Visual Chronometer paper)"
    )
    
    generate_btn.click(
        fn=generate_video,
        inputs=[api_key, prompt, model, duration],
        outputs=[video_url, status]
    )
    
    gr.Markdown("""
    ---
    ## Links
    
    | Resource | Link |
    |---|---|
    | 🌐 NexaAPI | [nexa-api.com](https://nexa-api.com) |
    | 🚀 RapidAPI | [rapidapi.com/user/nexaquency](https://rapidapi.com/user/nexaquency) |
    | 🐍 Python SDK | `pip install nexaapi` |
    | 📦 Node.js SDK | `npm install nexaapi` |
    | 📄 Paper | [arXiv:2603.14375](https://huggingface.co/papers/2603.14375) |
    | 💻 Visual Chronometer | [GitHub](https://github.com/taco-group/Visual_Chronometer) |
    
    *Source: arXiv:2603.14375 | Fetched: 2026-03-27*
    """)


if __name__ == '__main__':
    demo.launch()