Video Generation
SkyReels Series
Kunlun Wanwei SkyReels V4 — multimodal T2V/I2V/Omni video, with reference images, video extension, and voiceprint sync
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SkyReels Series
Kunlun Wanwei SkyReels V4 video generation series.
V4 is the multimodal release of SkyReels. Beyond T2V / I2V, it natively supports Omni multi-asset references (image / video / audio), video extension, first/last frame & mid-frame keyframes, voiceprint sync, and other advanced capabilities. Duration is any integer in 3-15 seconds.
Billed by resolution × duration, with two tiers — Fast / Std:
Both tiers share the same parameters and capabilities (actions / ref_images / ref_videos / mid_frame_images / voiceprint) — they only differ in sampling depth. Recommended workflow: prototype with fast, render the final cut with std.
After submission, poll status with
Reference asset list, up to 6 items. Each item can be a single image or a multi-image grid, and may bind a driving audio clip.
Video asset list, up to 1 item.
Define key frames in the middle of the video, up to 6 items, interpolated by timestamp. Often combined with first/last frames to precisely choreograph shot pacing.
| Tier | Positioning | Speed | Quality | Recommended Scenarios |
|---|---|---|---|---|
skyreels-v4-fast | Fast tier | Quick | Standard | Creative previews, batch drafts, A/B comparisons |
skyreels-v4-std | Standard quality tier | Slower (~1.5-2x) | More stable | Final delivery, client-facing cuts, complex motion shots |
Pricing
Billed per second ($ / sec). When video reference is enabled (ref_videos containing extend or reference types), a separate unit price applies:
skyreels-v4-fast
| Resolution | Standard | With Video Reference | 5-second video (standard) |
|---|---|---|---|
| 480P | $0.068 / sec | $0.1275 / sec | $0.34 |
| 720P | $0.0935 / sec | $0.17 / sec | $0.4675 |
| 1080P | $0.23375 / sec | $0.425 / sec | $1.16875 |
skyreels-v4-std
| Resolution | Standard | With Video Reference | 5-second video (standard) |
|---|---|---|---|
| 480P | $0.0935 / sec | $0.153 / sec | $0.4675 |
| 720P | $0.119 / sec | $0.2125 / sec | $0.595 |
| 1080P | $0.2975 / sec | $0.53125 / sec | $1.4875 |
Video reference surcharge — when
ref_videos contains any item of type reference (video reference) or extend (video extension), pricing follows the “With Video Reference” column; otherwise the standard column.Examples
GET /v1/tasks/{task_id}. See Task System for details.
Mode Cheat Sheet
Switch generation modes via theaction field (or the corresponding media fields):
| Mode | action | Key Fields | Typical Use |
|---|---|---|---|
| Text-to-video | generate | prompt | Pure text generation |
| Image-to-video | image2video | first_frame_image | Animate a single frame |
| First/last frame inpainting | first_last_frame | first_frame_image + last_frame_image | Precisely control start/end frames |
| Multi-image reference (Omni) | reference | ref_images | Character / style / scene consistency |
| Video reference | reference_video | ref_videos.type=reference | Replicate camera motion / style |
| Video extension | extend | ref_videos.type=extend | Continue an existing video |
| Audio-driven | reference_audio | audio_urls or ref_images[].audio_url | Voiceprint / beat sync, lip-sync |
Available Models
| Model ID | Tier | Resolution | Duration | Description |
|---|---|---|---|---|
skyreels-v4-fast | Fast tier | 480P / 720P / 1080P | 3-15 sec | Full T2V/I2V/Omni capability, faster response |
skyreels-v4-std | Standard quality tier | 480P / 720P / 1080P | 3-15 sec | Same capability as fast, more stable quality, suited for final delivery |
Common Parameters
Model ID. Allowed values:
skyreels-v4-fast— fast tierskyreels-v4-std— standard quality tier
Operation type. The backend usually auto-routes based on media fields; passing explicitly locks the mode. Allowed values:
generate— text-to-video (T2V)image2video— image-to-video (I2V), withfirst_frame_imagefirst_last_frame— first/last frame inpainting, withfirst_frame_image+last_frame_imagereference— multi-image reference (Omni style / character consistency), withref_imagesreference_video— video reference, withref_videos.type=referencereference_audio— audio-driven, withaudio_urlsorref_images[].audio_urlextend— video extension, withref_videos.type=extend
Video description, up to 5000 characters. Required for T2V; optional as guidance for other modes
Frame aspect ratio. Effective in T2V; modes containing media assets follow the source media’s ratio. Allowed values:
16:9— landscape widescreen9:16— portrait tall4:3— landscape3:4— portrait1:1— square
Output resolution. Allowed values:
480p720p1080p
Video duration in seconds, any integer in 3-15
Reference image URL array (simplified mode), one of
image_urls or ref_images. For complex cases (need to specify tag / type=image|grid / bind audio_url) use ref_imagesFirst-frame image URL, triggers I2V mode
Last-frame image URL. When passed alongside
first_frame_image, triggers first/last frame inpaintingReference video URL array (simplified mode), one of
video_urls or ref_videos. For complex cases (need to specify tag / type=reference|extend) use ref_videosReference audio URL array (simplified mode), triggers voiceprint sync (
reference_audio mode), one of audio_urls or the audio_url field inside ref_images. For complex cases (binding audio to a specific asset, linked with image / style group) use ref_images[].audio_urlWebhook callback URL, invoked when the task reaches a terminal state. See Callbacks
Callback event subscription list. By default subscribes to terminal states (
succeeded / failed). Allowed values:queued— enqueuedrunning— execution startedsucceeded— success (default)failed— failure (default)
Model-Specific Parameters
Both tiers share identical parameters; they differ only in generation speed and quality. Choose by scenario.- skyreels-v4-fast
- skyreels-v4-std
Positioning: fast tier, quicker response, suited for previews / drafts / high-throughput scenarios.
Omni multi-image reference, up to 6 items. Each item supports
image (single image) or grid (multi-image composite), and may include audio_url as the driving audio. See Composite Field Reference belowVideo reference, up to 1 item.
type=reference for style / character reference; type=extend for video continuation. See Composite Field Reference belowMid-frame keyframes, up to 6 items, with timestamps. Combine with
first_frame_image / last_frame_image to precisely control motion trajectory. See Composite Field Reference belowWhether to enable intelligent prompt rewriting. When on, the backend expands prompt details to improve generation stability; when off, the original prompt is followed strictly
Composite Field Reference
SkyReels V4’s multimodal capabilities are expressed via three array fields, with semantics more precise than the genericimage_urls / video_urls. Recommended for complex scenarios.
ref_images — Omni multi-asset reference
Reference asset list, up to 6 items. Each item can be a single image or a multi-image grid, and may bind a driving audio clip.
| Field | Type | Required | Description |
|---|---|---|---|
tag | string | Yes | Asset tag, injected into prompt context. e.g. char / style / bg |
type | string | Yes | image — single image; grid — multi-image composite (2-9 images forming one semantic group) |
image_urls | string[] | Yes | Image URL array. Length 1 when type=image; 2-9 when type=grid |
audio_url | string | No | Audio bound to this asset (voiceprint / beat driving), WAV / MP3 |
ref_videos — video reference / video extension
Video asset list, up to 1 item. type decides the semantics: style reference vs. video continuation.
| Field | Type | Required | Description |
|---|---|---|---|
tag | string | Yes | Asset tag, e.g. src / style_ref |
type | string | Yes | reference — style / character / motion reference; extend — video continuation, the new video is appended to the source |
video_url | string | Yes | Video URL, MP4 / MOV |
Pricing reminder — when any item in
ref_videos is reference or extend, the +video_ref surcharge applies.mid_frame_images — mid-frame keyframes
Define key frames in the middle of the video, up to 6 items, interpolated by timestamp. Often combined with first/last frames to precisely choreograph shot pacing.
| Field | Type | Required | Description |
|---|---|---|---|
tag | string | Yes | Keyframe tag, e.g. kf_2s / peak |
image_url | string | Yes | Keyframe image URL |
time_stamp | number | Yes | The frame’s appearance time (seconds), must lie in (0, duration) and be strictly increasing |
Prompt Writing Tips
SkyReels V4’sprompt_optimizer is on by default, but writing a clear prompt still significantly improves output quality:
- Camera language — be explicit about camera motion (push / pull / pan / follow) and shot size (close-up / wide / overhead). Example:
slow camera push-in, from wide shot to facial close-up - Pacing control — segment with time words. Example:
still gaze for the first 2 seconds, then turn and walk away over the next 3. Pairs well withmid_frame_images - Style anchoring — describe lighting / color palette / texture. Example:
cinematic cool tones, natural backlight, film grain - Avoid negatives — V4 does not support
negative_prompt. Rewrite “no X” as a positive description - Multi-asset guidance — when using
ref_images, name the tag in the prompt. Example:keep the char consistent, walking through the style scene
Resource Limits
| Item | Limit |
|---|---|
ref_images | Up to 6 items, 2-9 images per type=grid item; each image ≤ 30MB, JPG/PNG/WEBP |
ref_videos | Up to 1 item, MP4/MOV, ≤ 100MB, 2-30 seconds |
mid_frame_images | Up to 6 items, timestamps must be strictly increasing and within (0, duration) |
audio_urls / audio_url | WAV/MP3, ≤ 15MB, 3-30 seconds |
first_frame_image / last_frame_image | JPG/PNG/WEBP, ≤ 30MB |
| Output | MP4, link valid for 24 hours |
| Concurrency | ≤ 5 queued tasks per account at the same time |
Related Docs
- Task System — task state machine / polling cadence / async push
- Request & Response Format — common error codes / Headers / rate limits
- Authentication — API Key issuance and usage
- Callbacks — Webhook signing / retries / event subscriptions
SkyReels Series