Image to video API

How image-to-video differs from text-to-video

You supply the first frame, so composition, subject and style are already decided — the model only has to produce motion. That makes output far more controllable than text-to-video, and it composes naturally with the image models here: generate a still, approve it, then animate it.

The clip preserves the aspect ratio of your start frame. The prompt describes motion, not content.

• Describe camera and subject movement: "slow push in, hair moving in the wind"
• Static or near-static prompts produce subtle, ambient motion — often what you want for backgrounds
• The start frame carries the quality: a sharp, well-composed still animates far better than a soft one

Generate a clip

curl https://api.fastgencloud.com/v1/videos/generations \
  -H "Authorization: Bearer $FASTGEN_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
      "model": "image-to-video",
      "image": "https://example.com/still.jpg",
      "prompt": "slow push in, gentle wind moving the leaves, drifting clouds",
      "duration": 5
    }'

Latency and cost

Video is the slowest and most expensive operation on the platform, and worth designing around. A 5 second clip typically takes on the order of three minutes on a warm 48 GB worker; a cold start adds more. Use a webhook rather than polling in a request handler, and tell your users it is a background job.

Billing is per second of output, so a 5 second clip costs five times the per-second rate and an 8 second clip eight times.

Parameters

model

image-to-video

image

start frame — https URL or data URI; aspect ratio preserved

prompt

optional motion description, up to 1500 characters

negative_prompt

optional, verbatim

duration

5 or 8 seconds

seed

optional integer for reproducible output

webhook_url

strongly recommended for video

How the API works

Every generation is a job. The POST returns 202 with a job id immediately, so your request thread is never blocked on a GPU. You then either poll GET /v1/jobs/{id} or register a webhook_url and receive a signed callback when the job finishes.

Send an Idempotency-Key header and a retried request replays the original job instead of charging you twice. Your wallet is debited when the job is submitted and refunded automatically if it fails.

curl https://api.fastgencloud.com/v1/jobs/$JOB_ID \
  -H "Authorization: Bearer $FASTGEN_API_KEY"

Pricing and billing

Pricing is prepaid and usage-based: you top the wallet up with a card and each job debits it. There is no subscription, no per-seat cost, and no monthly minimum.

Images above 1 megapixel are billed pro rata by pixel count — a 1.5 MP image costs 1.5x the listed rate. Failed jobs are refunded in full, automatically.