Runway Video Generation Compared: How to Choose Across Generate, Extend, and Aleph

Introduction: The Runway Video Creation Stack

Runway helped define the modern AI video workflow: create from text or images, continue a story on an existing render, and restyle footage while preserving motion structure. On FuseAI Tools, three named flows—generate, extend, and aleph—map cleanly to that lifecycle.

Many creators ask the same question: when should I generate fresh pixels, when should I extend a prior Runway task, and when should I run Aleph on uploaded video? This guide aligns each scenario with representative API parameters and the exact route on the platform.

Runway hub: /home/runway

I. Snapshot: Three Scenarios at a Glance

Scenario	Core function	Primary inputs	Duration / resolution	Positioning
generate	Text-to-video / image-to-video	prompt (+ optional imageUrl)	5s or 10s · 720p / 1080p	Create from zero
extend	Video continuation	taskId + prompt	Matches source · 720p / 1080p	Continue a Runway clip
aleph	Video style / scene transform	videoUrl + prompt (+ optional referenceImageUrl)	Inherits source length	Style migration on existing video

II. Three Scenarios Deep Dive

Scenario 1: generate (text-to-video / image-to-video)

Start from language—or animate a still image—without any prior Runway task.

{
  "prompt": "Descriptive text for the scene (max 1800 characters)",
  "imageUrl": "Optional reference image URL",
  "duration": 5,
  "quality": "720p",
  "aspectRatio": "9:16",
  "waterMark": "FuseAi"
}

Modes:

Mode	Input	Output	Aspect ratio
Text-to-video	prompt only	New clip	Set via aspectRatio
Image-to-video	prompt + imageUrl	Animated still	Follows uploaded image

Duration vs quality: 720p supports both 5s and 10s. 1080p is limited to 5s only—10-second jobs must stay at 720p on the FuseAI Tools UI.

Aspect ratios (text-only): 16:9, 9:16, 4:3, 3:4, 1:1—pick platform fit before you prompt (YouTube vs Shorts vs square social).

Best for: concept reels, product motion from stills, ad previsualization, social shorts from scratch.

Route: /home/runway/generate

Scenario 2: extend (video continuation)

Append a sequel to a clip that was produced with Runway generate. The UI lists eligible tasks from your account history.

{
  "taskId": "Original Runway generate task ID",
  "prompt": "What should happen next (max 1000 characters)",
  "quality": "720p",
  "waterMark": "FuseAi"
}

Inheritance from the parent clip:

Property	Inherited?
Resolution / aspect ratio	✅ Aligned with source
Visual style / palette	✅ Strong continuity
Subject / scene logic	✅ Prompt steers the sequel
Clip length	✅ Matches original duration

Constraint: taskId must reference a completed Runway generate job—not arbitrary uploads.

Best for: serial storytelling, finishing truncated generations, episodic social content.

Route: /home/runway/extend

Scenario 3: aleph (video style conversion)

Transform an existing video (any source you can upload) while keeping motion and structure; steer look and atmosphere with text and an optional reference still.

{
  "prompt": "Describe the target style or scene change",
  "videoUrl": "Reference video URL (uploaded in UI)",
  "waterMark": "FuseAi",
  "aspectRatio": "16:9",
  "seed": 123456,
  "referenceImageUrl": "Optional style reference image URL"
}

vs generate:

Contrast	generate	aleph
Input anchor	Text (+ optional image)	Video + text (+ optional reference image)
Output	Brand-new footage	Restyled version of source
Motion structure	N/A (created fresh)	Preserved from source video

Advanced knobs: seed improves reproducibility; referenceImageUrl nudges palette and art direction; aspectRatio sets output framing (16:9, 9:16, 4:3, 3:4, 1:1, 21:9 on FuseAI Tools).

Best for: anime or film-grade regrades, seasonal or weather swaps, stylized ads, turning live action into illustrated motion.

Route: /home/runway/aleph

III. Comparison Summary

3.1 Capability matrix

Feature	generate	extend	aleph
Text-to-video	✅	❌	❌
Image-to-video	✅	❌	❌
Continue Runway output	❌	✅	❌
Style transfer on video	❌	❌	✅
Requires reference video	❌	❌	✅
Requires prior taskId	❌	✅	❌
User-picked aspect ratio	✅ (no image)	Inherited	✅
Reference still for style	Optional imageUrl	❌	Optional referenceImageUrl

3.2 Input / output snapshot

Scenario	Typical input	Output	Duration
generate	prompt (+ imageUrl)	New video	5s or 10s
extend	taskId + prompt	Continuation clip	Same as parent
aleph	videoUrl + prompt (+ referenceImageUrl)	Transformed video	Same as source

3.3 Hard limits to remember

generate: 1080p only when duration is 5s; 10s forces 720p.
extend: taskId must come from a finished Runway generate job in your history.
aleph: requires a valid uploaded videoUrl; optional seed and reference image refine repeatability and look.

IV. Selection Decision Tree

What is your starting asset?
|
|-- Nothing yet (idea or still image)
|   |-- Have a reference image -> generate + imageUrl
|   `-- Text only -> generate
|
|-- A clip you made with Runway generate
|   `-- Want more story on the same timeline -> extend
|
`-- Any finished video file (your shoot or download)
    `-- Want new look / season / style, same motion -> aleph

V. Practical Payload Examples

Vertical social short (generate)

{
  "prompt": "A corgi chasing butterflies on sunlit grass, playful handheld feel",
  "duration": 5,
  "quality": "1080p",
  "aspectRatio": "9:16"
}

Product still to motion (generate)

{
  "prompt": "Slow orbit around the product, soft studio lighting",
  "imageUrl": "https://example.com/product.jpg",
  "duration": 5,
  "quality": "720p"
}

Story continuation (extend)

{
  "taskId": "ee603959-debb-48d1-98c4-a6d1c717eba6",
  "prompt": "The cat keeps dancing; disco lights spin faster around the room",
  "quality": "720p"
}

Animated regrade (aleph)

{
  "prompt": "Convert to warm Ghibli-inspired animation, gentle film grain",
  "videoUrl": "https://example.com/input.mp4",
  "aspectRatio": "16:9",
  "seed": 12345
}

VI. Final Recommendations

Use case	Feature	Why
Create from scratch	generate	Full control of duration, quality, and aspect ratio
Animate a still	generate + imageUrl	Image anchors composition; prompt drives motion
Extend a Runway clip	extend	Preserves lineage via taskId
Restyle existing footage	aleph	Keeps structure; changes look and mood

One-line playbook:

From scratch → generate.
Continue a Runway render → extend.
Restyle any video → aleph.

The three modes form a loop: generate seeds the timeline, extend lengthens the narrative, and aleph can reinterpret any footage without reshooting. Open every Runway mode from the hub: /home/runway.