Joining AI clips into a festival-length film

Two tools join separate clips into one file: Runway, through its Stitch Videos app, and SceneMixer, which composites an episode's segments. LTX Studio has a timeline editor, Higgsfield returns an edited scene from one generation, and Google Flow, Midjourney and Sora extend a single clip. From 9 source pages, read 2026-09-25; no maker pays to be listed.

Fig. 1 Both sides are dated readings of the organisers' and makers' own pages.

Fig. 2 Filled: the maker's pages state it. Hollow: not stated.

Joining clips into a film, by tool, read 2026-09-25.
Tool	Reading	In their words
Google Flow	One clip extended	Eight-second Veo 3.1 videos can be extended; joining separate clips is not described
Higgsfield	Several shots per generation	Cinema Studio returns an edited scene from one panel rather than a single raw clip
LTX Studio	A timeline editor	A timeline editor and dynamic storyboard in LTX Studio, from script to final delivery
Midjourney	One clip extended	A video can be extended after it is made; joining separate clips is not described
Runway	Clips joined into one file	Stitch Videos joins clips into one file, up to 60 minutes in all
SceneMixer	Clips joined into one file	Compositing joins an episode's segments into one file
Sora	One clip extended	A finished video can be extended into a new, stitched result

Inclusion rule. All 7 tools on the filmmaking-tools register. Order. Alphabetical by tool name.

Extending and joining are different operations. An extension continues one shot, so the camera and the action carry on; joining puts separate shots end to end, which is how a scene is cut.

Where a tool does not join clips itself, they go to an editing program. The AI Shortest Film Competition expects that step: its rules allow editing through an XML export.

Keeping the film inside one tool also matters where a festival wants to see the working. Higgsfield's festival asks entrants to keep every generation in one Cinema Studio project so entries can be checked.

1The rule it answers to

Fig. 3 Filled: the rules state it.

Festivals asking for three minutes or more, read 2026-09-25.
Festival	Running time	In the rules
1 Billion AI Film Award	A minimum and a maximum	7 to 10 minutes, subtitled in English
Astana AI Film Festival	A minimum only	3 minutes or longer
Higgsfield Global Film Festival	A minimum only	At least 3 minutes; 5 minutes recommended as a maximum, longer still eligible
Runway AI Festival	A minimum and a maximum	3 to 15 minutes
World AI Film Festival	A minimum and a maximum	5 to 10 minutes for short films
World AI Film Festival USA	Set per category	Set per category: 3 to 40 minutes for shorts, 40 minutes and up for features, 30 seconds to 3 minutes for vertical

Inclusion rule. Festivals whose rules set a minimum running time of three minutes or more. Order. Alphabetical by festival name.

The two rules mentioned above

Created with LTX – Up to 60 seconds long – Post-production/editing is allowed via XML export
Forward Festival, AI Shortest Film Competition by LTX

in which all AI video and image generations for an Entry must be kept
Higgsfield Global Film Festival, official rules

Requirements
The clip must be created with LTX; editing allowed via XML exportForward Festival, AI Shortest Film Competition by LTX / recorded 2026-09-25
At a glance
All AI video and image generations kept in one Cinema Studio festival projectHiggsfield Global Film Festival, official rules / recorded 2026-09-25

Every festival's reading, with the organiser's words: Running time allowed at every festival.

2In the makers' words

Google Flow

All Veo 3.1 8s videos can be extended
Google Flow Help, models and supported features

Veo 3.1 tip
Eight-second Veo 3.1 videos can be extended; joining separate clips is not describedGoogle Flow Help, models and supported features / recorded 2026-09-25

Google Flow on all four points

Higgsfield

get a finished, edited scene, not a raw clip
Higgsfield, Cinema Studio page

Cinema Studio 4.0
Cinema Studio returns an edited scene from one panel rather than a single raw clipHiggsfield, Cinema Studio page / recorded 2026-09-25

Higgsfield on all four points

LTX Studio

From scripting and storyboarding to editing and final delivery
LTX Studio page

Tools to streamline video production
A timeline editor and dynamic storyboard in LTX Studio, from script to final deliveryLTX Studio page / recorded 2026-09-25

LTX Studio on all four points

Midjourney

This will add another 4 seconds to your video.
Midjourney documentation, Video

Extend Video
A video can be extended after it is made; joining separate clips is not describedMidjourney documentation, Video / recorded 2026-09-25

Midjourney on all four points

Runway

Stitch Videos lets you combine multiple video clips into a single video file.
Runway Help Center, Stitch Videos

Introduction
Stitch Videos joins clips into one file, up to 60 minutes in allRunway Help Center, Stitch Videos / recorded 2026-09-25

Runway on all four points

SceneMixer

compositing joins them into one file for the episode
SceneMixer guide, compositing and sharing

Quick answer
Compositing joins an episode's segments into one fileSceneMixer guide, compositing and sharing / recorded 2026-09-25

SceneMixer on all four points

Sora

Video extensions let you continue an existing completed video and create a new stitched result.
OpenAI API, video generation guide

Extend completed videos
A finished video can be extended into a new, stitched resultOpenAI API, video generation guide / recorded 2026-09-25

Sora on all four points

3The other questions

4Pages read

Google Flow Help, models and supported features, read 2026-09-25
Higgsfield, Cinema Studio page, read 2026-09-25
LTX Studio page, read 2026-09-25
Midjourney documentation, Video, read 2026-09-25
Runway Help Center, Stitch Videos, read 2026-09-25
SceneMixer guide, compositing and sharing, read 2026-09-25
OpenAI API, video generation guide, read 2026-09-25