ViduS1 API

What is ViduS1 API

Vidu S1 is a commercial-grade streaming video generation model for real-time interactive digital humans. Through the Vidu S1 API, developers create live sessions in which an AI character sees, hears and talks with users — with unlimited-duration generation, 50+ voices and 28 languages. Unlike text-to-video models that render clips offline, Vidu S1 generates live video while the conversation happens: your user speaks, the character sees and hears them, and answers in quasi real time — with expression, voice and personality.

How to use ViduS1 API

Integrate the Vidu S1 API in 6 steps:

1. Create a Session – One POST call to /live/v1/lives with your character's persona, avatar image and voice returns a session ID plus RTC credentials.
2. Join the RTC Channel – Join the AliRTC channel with the returned token, publish your user's microphone (and camera in video mode), then subscribe to the character's stream.
3. Open the WebSocket – Connect the persistent control channel at wss://api.vidu.com/live/ws/live/connect with authentication in the query string.
4. Wait Until Ready – A success ack means the character is live. NOT_READY is normal in video mode — reconnect with exponential backoff (2s → 4s → 8s).
5. Keep the Session Alive – The server pings every 5 seconds; respond within 15. Listen for forced-disconnect messages.
6. Hang Up & Query Billing – Send the hangup message, close the WebSocket, leave the RTC channel — then query the final status and billed seconds.

Features of ViduS1 API

• Commercial-Grade Interaction – The first production-ready digital character with bidirectional perception: it interacts, performs and reacts to what it sees and hears from your users.
• Unlimited Interactive Duration – Supports unlimited-length interaction from 1 minute to 2 hours of continuous generation without quality degradation.
• Quasi Real-Time Response – Industry-leading inference speed with strong instruction following and semantic understanding.
• Personas with Memory – Define any initial persona — real human, anime character or cute pet. Short-term memory keeps conversations personal and consistent.
• Multimodal Perception – Voice, text and video input in one session. The character accurately picks up on the user's appearance, expression and emotional state.
• High-Resolution Output – High-quality real-time interactive video generation, ready for consumer-facing products.
• 50+ Voices, 28 Languages – Every voice supports 28 languages including English, Chinese, Japanese, Korean, French, German, Spanish, Portuguese, Russian, Arabic and Hindi. Regional dialects also available.
• Voice Cloning API – Create custom cloned voices via POST /live/v1/voices/clone.
• Simple API Surface – HTTP for session management, AliRTC for audio/video transport, WebSocket for control signaling.

Use Cases of ViduS1 API

• AI Companionship – Always-on characters with persona and memory that chat face-to-face, react to moods and build long-term bonds.
• Virtual Idols – Anime or realistic idols that host live shows, take fan questions and perform for hours without breaks.
• Training & Education – Tutors and trainers that explain, demonstrate and adapt to each learner's questions in real time.
• AI Customer Service – A friendly face for support: perceives frustration, answers naturally and hands off smoothly when needed.
• Live-Stream Commerce – Digital hosts that present products around the clock and answer buyer questions the moment they're asked.
• Interactive Entertainment – Playable characters and shadow-play experiences where the story reacts to the player's voice and face.

Pricing

• Free Trial – 1,000 credits for every new user (about 11 minutes of live interaction). Full API access, all voices and languages, audio and video modes.
• Pay As You Go – 3 credits per 2 seconds. Billing starts only when the character goes live. Deducted every 6 seconds, rounded to 2-second intervals. Sessions up to 600 seconds, auto-renewable. Minimum balance: 45 credits per session.
• Enterprise – Custom pricing with dedicated account manager, custom character and persona design, voice cloning onboarding support, and architecture review.

FAQ

What is Vidu S1? Vidu S1 is a commercial-grade streaming video generation model for real-time interactive digital humans. Through the Vidu S1 API, developers create live sessions in which an AI character sees, hears and talks with users — with unlimited-duration generation, 50+ voices and 28 languages.

When does billing start and how is usage metered? Billing starts the moment the digital character becomes ready and the session enters on_live — exactly when conn_init_ack.success returns true. The rate is 3 credits per 2 seconds, deducted every 6 seconds and rounded up to the nearest 2-second interval. Audio and video modes cost the same.

Can I interact with the digital character over HTTP only? No. HTTP is used to create and query sessions. Real-time audio and video are transmitted through the AliRTC channel (a separate SDK integration), and session control runs over a WebSocket signaling connection. All three channels together make one live session.

What should I do when the WebSocket returns NOT_READY? NOT_READY is expected in video mode — the character side is still preparing. Close the connection, wait briefly, reconnect and resend the init message, using exponential backoff (2s → 4s → 8s). If you receive LIVE_CONN_INIT_FAILED instead, that's permanent: create a new session.

How long can a single session last? The maximum session duration is 600 seconds; the server auto-disconnects when it's reached. For longer experiences, create a new session and reconnect — the underlying model itself supports continuous generation from 1 minute up to 2 hours without quality loss.

What happens when my credit balance reaches zero? The server automatically closes the connection with a credit_insufficient hangup reason. Each new session also requires a minimum balance of 45 credits to start.

Which languages and voices are available? 50+ preset voices, each supporting 28 languages including English, Chinese, Japanese, Korean, French, German, Spanish, Portuguese, Russian, Arabic and Hindi. Regional dialect voices (Cantonese, Sichuanese, Hokkien, Taiwanese Mandarin and more) are also available, and you can clone custom voices via the API.

Which API host should I use? Use api.vidu.cn for mainland China deployments and api.vidu.com for international ones. Authentication is a simple header: Authorization: Token vda_xxx. For WebSocket connections, pass the token in the authorization query parameter instead.

What avatar images can I use for the character? A single image with one person — full-body or half-body, any style (photoreal, anime, pet). PNG, JPG, JPEG or WEBP up to 50 MB, passed as a URL or Base64. Combined with a free-form persona prompt, it defines how your character looks and behaves.