How must the first-frame image be submitted?
Use image_url to submit a publicly accessible image, and set action to image_to_video and model to happyhorse-1.1-i2v. The image will serve as the first video frame; prompt is used to supplement subsequent actions, environmental changes, and camera movement, so there is no need to redescribe all static details.
Can I specify a vertical or square video?
The output aspect ratio for first-frame tasks should follow the image as closely as possible, with no need to pass ratio separately. To create vertical or square content, prepare a first frame with the corresponding composition first; it is best to leave safe space around product labels, people's heads, and other important elements, then check the actual final video frame.
Can it use multiple reference images to keep characters consistent?
This model starts generation from a single first-frame image and is not a multi-image reference mode. If you need to combine references for characters, clothing, or props, choose happyhorse-1.1-r2v; if the main goal is to make an existing image start moving without reorganizing the scene, i2v better matches the task structure.
What resolutions, durations, and audio capabilities are supported?
This endpoint offers 720P or 1080P, with durations of whole numbers from 3–15 seconds; native video specifications are 24 fps, MP4, with audio support. Audio generation and precise dubbing control are different capabilities; retaining the original video audio or using reference audio input cannot be used with this model.
How do I get the finished video after submission?
You can set async=true, save the returned task_id, and then query through /happyhorse/tasks; you can also provide callback_url to wait for a completion notification. Result statuses include pending, succeeded, and error, and successful results include video_url; do not assume the video has been generated just because you have obtained a task ID.