Introduction
Vidu Q4 Preview Video extend continues a clip you already have. Send it as video_url with a prompt for what happens next. The final frame of your clip becomes the opening frame of a new Vidu Q4 Preview image-to-video shot of 3 to 16 seconds, and the two are joined into one MP4: your original first, then the continuation, with the repeated seam frame removed. The new segment also comes back as its own file, so you can keep extending or edit the pieces separately.
Key features & highlights
Continuity comes from the last frame. Wardrobe, set, light and where everyone stands carry over because the new segment literally starts on your final frame. Motion does not carry over the same way: the model sees one still, not the whole clip, so describe the movement you want to continue instead of assuming it will keep its speed or direction.
One file back, plus the new piece on its own. The joined MP4 keeps your clip’s frame rate and its framing, with no black bars. To line the seam up, the picture may be trimmed or adjusted by a few percent at the edges. If the model returns a noticeably different shape, the new segment is scaled to fill your frame and centered, cropping what spills over. The file is encoded as H.264 MP4 with AAC sound. Sound from your source stays; sound generated for the new segment follows it; a silent side is padded with silence so picture and sound stay in step at the seam. The second asset in the output is the new segment alone, ready for another extend or for an editor.
Everything else is Vidu Q4 Preview image-to-video. The new segment runs on the same routes, with the same content range and the same per-second price as the image-to-video endpoint, and a failed generation is refunded the same way. That includes its refusals: requests at the Very strong level are refused, and refused requests are not charged. If the generation succeeds but the join itself cannot be built, the task fails and the charge is refunded.
Request parameters
| Parameter | Required | Description |
|---|---|---|
prompt | Yes | Required, up to 20,000 characters. What happens next: the action that follows, the camera move and the sound. at least 1 characters · at most 20000 characters |
video_url | Yes | The clip to continue: MP4, MOV or WebM, up to 60 seconds. Its final frame becomes the opening frame of the new segment, so cut it on a clean, sharp frame. at least 1 characters |
resolution | No | Sharpness of the generated new segment: 540p, 720p, 1080p, 2k or 4k, default 720p. |
duration_seconds | No | Length of the new segment: any whole number from 3 to 16. Defaults to 5. |
generate_audio | No | On by default, so the new segment comes with generated sound. Your source keeps its own sound either way; when one side is silent, the joined file is padded with silence. Default: |
enable_prompt_expansion | No | Off by default. When on, the model rewrites and expands your prompt before generating; keep it off for literal direction. Default: |
seed | No | 0 to 2147483647. Hold it steady to compare one changed field at a time; drop it for variety. |
Pricing
Billed per second of the new segment at the resolution you choose; the source clip you send is not billed. Refused requests are not charged.
| Specification | Price |
|---|---|
| $0.045 / second |
| $0.095 / second |
| $0.12 / second |
| $0.19 / second |
| $0.39 / second |
Use cases
Lengthen a shot that ended too early: a product turntable that stops before the label faces camera, or a walk that cuts before the subject reaches the door. Extend it by a few seconds and describe only the remaining motion.
Build a longer sequence step by step. Generate a first shot, extend it, then extend the joined result again while it stays within the 60-second source limit; each step bills only the seconds it adds. Because every step starts from a single frame, watch each seam before stacking the next one.
Prompt guide & pro tips
Describe the next beat, not the whole scene. The frame already fixes who and where, so spend the prompt on the action that follows, the camera move and the sound. Repeat the camera language your clip ended on, such as a slow push in or a locked shot, so the seam reads as one take.
Trim before you extend. The last frame is the only thing the model sees, so a blurred, mid-cut or heavily compressed ending carries straight into the continuation. Cut your source on a clean, sharp frame first. Sources of up to 60 seconds are accepted as MP4, MOV or WebM.
Keep the resolution consistent. The resolution only decides how sharp the new segment is generated, so a lower setting makes the new part look softer than the original. Match the resolution of your source, and set duration_seconds to the length you actually need: the charge follows the new segment only.
API quick start
# Generate the idempotency key once; reuse it when retrying after a lost response.
export SPICY_IDEMPOTENCY_KEY="${SPICY_IDEMPOTENCY_KEY:-$(uuidgen)}"
curl -X POST https://api.spicyapi.ai/api/v1/jobs/createTask \
-H "Authorization: Bearer $SPICY_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: $SPICY_IDEMPOTENCY_KEY" \
-d '{
"model": "vidu/q4-preview/video-extend",
"input": {
"duration_seconds": 5,
"prompt": "A slow aerial shot drifting over a misty pine forest at sunrise",
"resolution": "720p",
"video_url": "https://example.com/reference.mp4"
}
}'
# Copy data.taskId from the response into TASK_ID, then poll the status.
TASK_ID="TASK_ID_FROM_RESPONSE"
curl "https://api.spicyapi.ai/api/v1/jobs/recordInfo?taskId=$TASK_ID" \
-H "Authorization: Bearer $SPICY_API_KEY"
See the API reference for authentication, the complete schema, polling, and error handling.
