MiniMax H3 Fast

MiniMax H3 Fast is MiniMax H3 on the Nunchux engine. It generates a video clip and its soundtrack together, in one request. The request is synchronous. There is no task to poll. Two model IDs serve it. They share one request shape, and the refs list carries the inputs:

Model	Model ID	Task	Inputs in `refs`
MiniMax H3 Fast	`nunchux-minimax-h3-fast-fl2va`	Text-to-video, or a clip that starts or ends on your frames	None, or a first frame, a last frame, or both
MiniMax H3 Fast	`nunchux-minimax-h3-fast-ref2va`	Reference-to-video	Reference images, reference clips and audio tracks

Both models have the Radical Speed and Radical Value tiers. A clip is 4 to 15 seconds long, with a short edge of 480 or 768 pixels. For MiniMax’s own H3 API, with its asynchronous task flow and 2K output, see MiniMax H3.

Endpoint

POST https://api.nunchux.com/v1/videos/generations

The older path /v1/video/generations still works, with the same result and the same billing, but it is deprecated. Use /v1/videos/generations in new code.

Request

Every request must include your API key and a JSON content type. See Authentication.

string

required

Your API key.

string

required

Must be application/json.

string

required

The model that generates the clip.Options: nunchux-minimax-h3-fast-fl2va, nunchux-minimax-h3-fast-ref2va

string

required

A text description of the clip. Describe the shot, what changes during the clip, and the sound. With references, name them by their order: Image 1, Video 1, Audio 1.

string

default:"radical_speed"

The balance of speed and cost. See Performance tiers.Options: radical_speed, radical_value

number

default:5.1667

The clip length in seconds. Range: 4 to 15. The model renders at 24 frames per second on a fixed frame grid, so the clip can run up to two-thirds of a second longer than your value. A request for 4 seconds returns a 4.46 second clip. The response gives the length of the clip.

array

The input media, in order. Each item names its role and a public https URL. On nunchux-minimax-h3-fast-fl2va, send no refs for text-to-video. See Inputs for the roles each model takes.

Show Item properties

string

required

What the input is for.Options: first_frame, last_frame, reference_image, reference_video, reference_audio

string

required

A public https URL of the file. An http URL returns a 400.

object

The shape of the clip.

Show properties

integer

default:768

The short edge of the clip in pixels. 768 costs more per second than 480.Options: 480, 768

string

default:"16:9"

The shape of the clip. The long edge follows the ratio, rounded to a multiple of 32, and the clip stays under about one megapixel. At 16:9, 480 gives 864x480 and 768 gives 1344x768. At 21:9, 768 gives 1536x672.Options: 21:9, 16:9, 4:3, 1:1, 3:4, 9:16

string

default:"off"

With any mode other than off, the prompt is rewritten into a detailed shot description before the clip renders. The rewriter sees your frames, images and clips. fast adds a few seconds. standard, balanced and quality give fuller rewrites and take longer. The response returns the rewritten prompt as revised_prompt.Options: off, fast, standard, balanced, quality

integer

The random seed. When you do not send a seed, the model selects one and returns it in the response. The same seed with the same parameters gives the same result.

boolean

default:true

Whether Nunchux’s content filter checks this request. Only accounts approved to turn moderation off may send false. Others get a 403. See Content moderation.

integer

default:1

The number of clips to generate. Only 1 is supported.

string

default:"b64_json"

The format of the returned clip.Options: b64_json, urlIn url format, Nunchux keeps the generated clip for 7 days, so that it appears in your request history. Then Nunchux deletes it. Save the clip from the response if you need to keep it.

Unsupported fieldsMiniMax H3 Fast does not accept width, height, steps, guidance_scale or negative_prompt. Set the shape with extra.short_edge and extra.aspect_ratio. A request that contains one of them returns a 400.

Inputs

Each model takes its own roles in refs. A role that the model does not take returns a 400.

Model ID	Role	Limit
`nunchux-minimax-h3-fast-fl2va`	`first_frame`	1 image. The clip starts on it.
`nunchux-minimax-h3-fast-fl2va`	`last_frame`	1 image. The clip ends on it.
`nunchux-minimax-h3-fast-ref2va`	`reference_image`	Up to 9 images
`nunchux-minimax-h3-fast-ref2va`	`reference_video`	Up to 3 clips, 2 to 15 seconds each, 15 seconds in all
`nunchux-minimax-h3-fast-ref2va`	`reference_audio`	Up to 3 audio tracks

nunchux-minimax-h3-fast-fl2va takes a first frame, a last frame, both, or neither. With neither, it generates the clip from the prompt alone. nunchux-minimax-h3-fast-ref2va needs at least one reference. A request with no refs returns a 400. In the prompt, name each reference by its role and its position in refs: the first reference_image is Image 1, the first reference_video is Video 1, and the first reference_audio is Audio 1. The files must meet these limits:

Images: up to 30 MB, each side 256 to 5760 pixels, and a width-to-height ratio from 0.4 to 2.5.
Clips: up to 50 MB, each side 256 to 5760 pixels, a width-to-height ratio from 0.4 to 2.5, and 23.976 to 60 frames per second. Send MP4 or MOV, so that Nunchux can read the clip length for billing.
Audio: up to 15 MB.

A minimal text-to-video body:

{
  "model": "nunchux-minimax-h3-fast-fl2va",
  "prompt": "A paper boat drifts down a rain-filled gutter at dusk, the patter of rain and a distant tram bell",
  "duration": 6,
  "extra": { "short_edge": 480, "aspect_ratio": "16:9" },
  "response_format": "url"
}

A body that starts and ends the clip on your frames:

{
  "model": "nunchux-minimax-h3-fast-fl2va",
  "prompt": "The flower opens slowly in the morning light, birdsong in the background",
  "duration": 6,
  "refs": [
    { "role": "first_frame", "url": "https://example.com/bud.png" },
    { "role": "last_frame", "url": "https://example.com/bloom.png" }
  ],
  "extra": { "short_edge": 768, "aspect_ratio": "1:1" },
  "response_format": "url"
}

A reference-to-video body:

{
  "model": "nunchux-minimax-h3-fast-ref2va",
  "prompt": "Reference the camera movement from Video 1, have the character in Image 1 sing, with the vocals matching Audio 1",
  "duration": 6,
  "refs": [
    { "role": "reference_image", "url": "https://example.com/singer.png" },
    { "role": "reference_video", "url": "https://example.com/camera-move.mp4" },
    { "role": "reference_audio", "url": "https://example.com/vocals.mp3" }
  ],
  "extra": { "short_edge": 480, "aspect_ratio": "16:9" },
  "prompt_expansion": "fast",
  "response_format": "url"
}

Response

The response is JSON. The data array contains one MP4 clip, with its soundtrack, as base64 data or as a URL.

integer

required

The Unix timestamp of the generation.

string

required

The model that generated the clip.

string

required

The tier that served the request: radical_speed or radical_value.

integer

required

The seed of the clip. Send it again to get the same result.

object

Returned when prompt_expansion is not off. mode is the mode you sent. outcome is expanded when the clip rendered from the rewritten prompt.

array

required

The generated clip.

Show Item properties

string

The MP4 clip as base64 data. Returned when response_format is b64_json.

string

The URL of the MP4 clip. Returned when response_format is url.

integer

The width of the clip in pixels.

integer

The height of the clip in pixels.

number

The length of the clip in seconds.

integer

The number of frames in the clip.

integer

The frame rate of the clip.

string

The rewritten prompt that the model rendered. Returned when prompt_expansion is not off and the rewrite succeeds.

{
  "created": 1234567890,
  "model": "nunchux-minimax-h3-fast-fl2va",
  "tier": "radical_speed",
  "seed": 1536904073,
  "data": [
    {
      "url": "https://...",
      "width": 864,
      "height": 480,
      "duration": 4.4583,
      "frames": 107,
      "frame_rate": 24
    }
  ]
}

Example

A clip takes some time to render. A 6 second clip at 480 takes about 6 seconds on Radical Speed and about 20 seconds on Radical Value. Set the timeout of your HTTP client to 120 seconds.

curl -X POST https://api.nunchux.com/v1/videos/generations \
  --max-time 120 \
  -H "Content-Type: application/json" \
  -H "X-API-Key: $NUNCHUX_API_KEY" \
  -d '{
    "model": "nunchux-minimax-h3-fast-fl2va",
    "prompt": "A paper boat drifts down a rain-filled gutter at dusk, the patter of rain and a distant tram bell",
    "tier": "radical_speed",
    "duration": 6,
    "extra": {"short_edge": 480, "aspect_ratio": "16:9"},
    "response_format": "b64_json"
  }' | jq -r '.data[0].b64_json // error(.error.message // .detail // tostring)' | base64 -d > output.mp4

import os
import base64
import requests

response = requests.post(
    "https://api.nunchux.com/v1/videos/generations",
    headers={
        "Content-Type": "application/json",
        "X-API-Key": os.environ["NUNCHUX_API_KEY"],
    },
    json={
        "model": "nunchux-minimax-h3-fast-fl2va",
        "prompt": "A paper boat drifts down a rain-filled gutter at dusk, the patter of rain and a distant tram bell",
        "tier": "radical_speed",
        "duration": 6,
        "extra": {"short_edge": 480, "aspect_ratio": "16:9"},
        "response_format": "b64_json",
    },
    timeout=120,
)
response.raise_for_status()

# Decode the base64 clip and save it. Change output.mp4 to any file name.
clip_b64 = response.json()["data"][0]["b64_json"]
with open("output.mp4", "wb") as f:
    f.write(base64.b64decode(clip_b64))

import { writeFile } from "node:fs/promises";

const response = await fetch("https://api.nunchux.com/v1/videos/generations", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "X-API-Key": process.env.NUNCHUX_API_KEY,
  },
  body: JSON.stringify({
    model: "nunchux-minimax-h3-fast-fl2va",
    prompt:
      "A paper boat drifts down a rain-filled gutter at dusk, the patter of rain and a distant tram bell",
    tier: "radical_speed",
    duration: 6,
    extra: { short_edge: 480, aspect_ratio: "16:9" },
    response_format: "b64_json",
  }),
  signal: AbortSignal.timeout(120_000),
});
if (!response.ok) throw new Error(`HTTP ${response.status}: ${await response.text()}`);
const data = await response.json();

// Decode the base64 clip and save it. Change output.mp4 to any file name.
await writeFile("output.mp4", Buffer.from(data.data[0].b64_json, "base64"));

Billing

A clip is billed per second of output video, at the rate of its tier and its short edge. 768 costs more per second than 480, and Radical Value costs less than Radical Speed. The billed seconds are the duration you send, not the slightly longer clip that returns. Inputs add to the charge only on nunchux-minimax-h3-fast-ref2va:

Each reference clip is billed per second of its length, at the same rate as the output. A clip whose length Nunchux cannot read, such as a WebM file, is billed as 15 seconds.
The first 5 reference images are free. Each image after the fifth has a fixed price.
Reference audio is free.

First and last frames on nunchux-minimax-h3-fast-fl2va are free. See the pricing page for current rates. Nunchux charges only for a successful clip. A request that fails is never billed.

Tips

Describe the sound in the prompt as well as the picture. The model generates both.
On nunchux-minimax-h3-fast-ref2va, say what each reference is for: the character in Image 1, the camera movement from Video 1, the voice in Audio 1.
Draft at 480 on Radical Speed. Use 768 for the final clip, and Radical Value for large batches.
Use prompt_expansion set to fast for a short prompt. Use off when your prompt already describes the shot in detail.
Keep the seed when you like a result. Then change one parameter at a time.

Errors and limits

Status	Code	Cause
400	none	`extra.short_edge` has no price, for example 1080. The body is a plain `detail` string that names the priced short edges.
400	`engine_error`	The model cannot render the request, for example a short edge other than 480 or 768, an aspect ratio off the list, a `duration` under 4 or over 15, an unsupported field, `n` above 1, a role the model does not take, too many references, or a reference URL that is not `https`.

Every request counts toward the requests-per-minute cap of your plan. A request also holds one simultaneous-jobs slot until the response returns. See Rate limits. For authentication and credit errors, see Error codes.

Get started

Guides

Nunchux Optimized models

Partner models

Resources

MiniMax H3 Fast

MiniMax H3 Fast

Endpoint

Request

Inputs

Response

Example

Billing

Tips

Errors and limits