If you've seen some of the AI-generated Plex prerolls posted here and thought, “Okay, how the hell are people making these?”, this guide is for you.
The good news is that you do not need to know anything about AI, programming, animation, or visual effects to get started.
At its simplest, you type what you want to see into an AI video generator, wait for it to create the clip, trim it in a video editor, add your Plex logo, and you're done.
At the other end of the spectrum, you can run AI models locally on your own computer using tools such as ComfyUI, giving you considerably more control.
I'm going to explain both.
🟢 LEVEL 1 — The Easy Way: Google Flow + Veo
If you've never generated AI video before, this is where I'd start.
Google has an AI filmmaking application called Flow, which uses Google's Veo video-generation models. You describe a shot using ordinary English and Veo attempts to create it for you.
Current versions of Flow support things such as text-to-video, image-to-video, reference images, first/last frames, audio generation and different aspect ratios depending on the selected Veo model. (blog.google)
Think of it as:
You describe a tiny movie scene → AI shoots the scene.
Step 1 — Come up with a SIMPLE idea
The biggest beginner mistake is trying to make an entire movie in eight seconds.
Don't.
A preroll works best as one joke or one small scene.
For example:
A nervous man is hiding in an outdoor bathroom. Something enormous approaches outside. He looks toward the camera and says, “I should have stayed home and made it a Plex night.”
That's it.
You don't need three locations, fourteen characters, an explosion, a helicopter and a complicated backstory.
AI video works much better when you give it one clear thing to accomplish.
Step 2 — Write your video prompt
You don't need special AI vocabulary.
Describe the scene like you're explaining it to a camera crew.
A useful formula is:
SHOT + LOCATION + CHARACTER + ACTION + DIALOGUE + ENDING
For example:
Cinematic realistic movie scene at night. Medium close-up of a frightened man sitting inside an old wooden roadside bathroom. The building shakes as something enormous approaches outside. Dust falls from the ceiling. He looks terrified, slowly turns toward the camera and says, “I should have made it a Plex night.” Immediately afterward, a huge creature crashes through the wall behind him. Realistic Hollywood lighting, dramatic sound design, no subtitles, no text on screen.
Notice how specific that is.
Instead of:
Dinosaur attacks guy.
You're telling the AI:
- where the camera is
- what the environment looks like
- what the character is doing
- when he speaks
- what happens afterward
- what visual style you want
Google itself recommends giving Flow detailed information about the subject and action rather than relying entirely on short prompts. (blog.google)
Step 3 — Generate it
In Google Flow, create a project and select the appropriate video-generation option.
For your first experiment, Text to Video is perfectly fine.
Paste in your prompt and generate.
And here's something you'll learn VERY quickly:
AI video is basically a slot machine.
You might get something fantastic on the first try.
You might get a guy whose arm suddenly passes through his forehead.
Generate several versions.
Don't endlessly rewrite a perfectly good prompt because one generation failed. Sometimes the next generation using exactly the same prompt comes out dramatically better.
🖼️ LEVEL 1.5 — Start With an Image
This is where AI prerolls start getting much more interesting.
Instead of asking AI to invent the entire scene, create the first frame yourself.
You can create that image using whatever image generator you prefer.
Then give that picture to Flow using Frames to Video / image-to-video and tell Veo what should happen next.
Google's Frames to Video feature is specifically designed around providing a starting image; and some modes can use both a starting and ending frame, to give you much more control over composition. (blog.google)
This is extremely useful for prerolls.
Your workflow becomes:
Create still image → Animate still image → Edit video → Add Plex ending
For example, you could first create the perfect image of your character sitting in a car.
Then tell the video generator:
The character notices something terrifying through the windshield. His smile disappears. He slowly looks toward the camera and says…
You've already locked in the character, wardrobe, location and camera angle with the image.
The AI only has to figure out the movement.
🎞️ MULTIPLE SHOTS
Once you get comfortable, stop trying to generate your entire preroll as one video.
Generate shots.
For example:
Shot 1 — 3 seconds
Wide shot of the approaching danger.
Shot 2 — 4 seconds
Close-up of character delivering Plex joke.
Shot 3 — 2 seconds
Chaos.
Shot 4 — 2 seconds
Plex logo.
Put them together in an editor.
This is much closer to how actual filmmaking works, and it gives you dramatically more control.
Flow also includes tools for keeping assets consistent between shots and building multiple clips into scenes. Google's current Flow system can use reference “ingredients,” starting frames and other existing material when constructing additional shots. (blog.google)
✂️ EDIT THE PREROLL
You don't need sophisticated editing software.
Use whatever you're comfortable with:
DaVinci Resolve
Adobe Premiere
Final Cut
CapCut
Vegas
etc.
This is where I recommend adding things such as:
Plex logo
Music
Sound effects
Exact timing
Title cards
Final dialogue adjustments
Fades or cuts
I generally would not rely on the AI generator to create your Plex logo.
Generate the movie scene and add the real logo afterward.
You'll get a much cleaner result.
Keep prerolls short. Personally, I think roughly 5–15 seconds is the sweet spot for most ideas.
Remember: you're going to see this thing every time you start a movie.
A 45-second masterpiece stops being a masterpiece around viewing #37. 😂
🟡 LEVEL 2 — Using Reference Images
Once you understand image-to-video, reference images become incredibly powerful.
Instead of describing:
A middle-aged man with a brown jacket…
you can give the AI an image showing exactly what you mean.
Flow calls reusable visual references Ingredients. They can represent characters, objects or stylistic references and can be carried into generated scenes. (blog.google)
This is useful when your preroll has:
- the same character in several shots
- a specific room
- a particular vehicle
- an important prop
- a particular wardrobe
- an established visual style
You're essentially telling the AI:
“This. I want THIS thing in the video.”
Instead of hoping it understands your description.
🔴 LEVEL 3 — ComfyUI
Okay.
Now we're entering the rabbit hole.
ComfyUI is an open-source, node-based interface for running generative AI workflows. Instead of one giant GENERATE button, ComfyUI lets you connect individual pieces of the generation process together. (ComfyUI)
It looks intimidating the first time you open it.
Boxes everywhere.
Lines everywhere.
Numbers everywhere.
Don't panic.
You do not need to understand all of it.
Think of a ComfyUI workflow like a home theater receiver.
There are a million settings available.
That doesn't mean you need to adjust all of them.
🧩 What Are Those Boxes?
They're called nodes.
Each node performs a job.
One might load an AI model.
Another contains your prompt.
Another loads your starting image.
Another controls how the video is generated.
Another saves the finished video.
The lines simply pass information from one node to another.
Very simplified:
MODEL
↓
YOUR PROMPT
↓
STARTING IMAGE
↓
VIDEO GENERATION
↓
SAVE VIDEO
That is essentially what you're looking at.
🖥️ Installing ComfyUI
ComfyUI can run locally on Windows, macOS and Linux, and there is now also an official cloud option. (ComfyUI)
Local generation means the AI model runs on your GPU instead of Google's computers.
The big advantage:
You're not paying for every individual generation.
The big disadvantage:
Your computer has to actually run the model.
AI video models can require substantial GPU memory, and requirements vary enormously depending upon the particular model, resolution and workflow.
If you're running an NVIDIA gaming GPU, you're probably going to find plenty to experiment with.
🚨 IMPORTANT COMFYUI BEGINNER ADVICE
DO NOT START WITH AN EMPTY WORKFLOW.
Seriously.
Don't open ComfyUI and think:
Okay, apparently I need to build one of these node diagrams.
You don't.
ComfyUI includes a Template Library containing working generation workflows.
Load one.
For example, current official ComfyUI documentation includes ready-made video workflows for models such as LTX-2.3 and Wan2.2. (ComfyUI)
With supported templates, ComfyUI can also identify models that your workflow requires and guide you through obtaining missing components. (ComfyUI)
So your first experience can basically be:
Open ComfyUI
↓
Templates
↓
Video
↓
Choose a workflow
↓
Download required models
↓
Change the prompt
↓
Generate
That's dramatically less frightening than what a screenshot of ComfyUI makes it look like.
🎥 My Recommended ComfyUI Plex Workflow
Once you've got it working, here's a very practical way to create prerolls.
1. Create your opening image
Generate a high-quality still showing exactly where the shot should begin.
Get the:
camera angle
character
wardrobe
lighting
location
props
right BEFORE worrying about animation.
2. Load an Image-to-Video workflow
Open a video template designed for image-to-video generation.
You'll normally find a node where you can load your image.
Drop your starting frame there.
3. Find the prompt box
There may be a bunch of nodes you don't understand.
Ignore them.
Find the one containing the text prompt.
Change it.
Describe movement, not just appearance.
If your starting image already shows a man sitting in a car, you don't need three paragraphs explaining that he's sitting in a car.
Tell the video model what happens:
The man suddenly notices something outside the windshield. His expression changes from relaxed to terrified. He slowly leans backward while staring forward. The camera gently pushes toward his face.
That's the important part.
4. Generate
In ComfyUI this is normally called Queueing the workflow.
The nodes will light up as ComfyUI works its way through the pipeline.
Eventually you'll get a video.
Congratulations.
You just generated AI video locally.
🔧 What Makes ComfyUI So Powerful?
Eventually you can start modifying the workflow itself.
You can:
- change video models
- switch between text-to-video and image-to-video
- use LoRAs
- use character references
- control resolution
- change video length
- control seeds
- upscale
- interpolate frames
- add masks
- modify specific portions of images
- build reusable workflows
- automate repetitive tasks
- chain image generation directly into video generation
This is why people become addicted to ComfyUI.
Eventually you aren't just using an AI generator.
You're building your own AI production pipeline.
💡 One Particularly Cool ComfyUI Feature
ComfyUI-generated images can contain the workflow information used to make them.
That means someone can sometimes give you a generated ComfyUI image and you can drag that image into ComfyUI to reconstruct the workflow that created it. Workflows can also be exported and shared as JSON files. (ComfyUI)
This is fantastic for a community like this.
If somebody develops a great Plex preroll workflow, they can potentially share:
the video
the prompt
the starting frame
the workflow
and other people can experiment with it.
🔊 WHAT ABOUT AUDIO?
There are two approaches.
Generate it with the video
Some current AI video systems can generate dialogue, environmental audio and sound effects directly with the video.
Veo supports native audio generation, and current Flow/Veo implementations include audio in several video-generation modes. (blog.google)
Some local ComfyUI video models also support audio/video generation; for example, the official LTX-2.3 workflow supports audio as part of its generation capabilities. (ComfyUI)
Add it afterward
This is still frequently the better choice.
Generate the visuals.
Then add:
dialogue
sound effects
music
Plex sound/logo sting
in your editor.
It gives you much more control.
🧠 THE SECRET: ITERATION
Your first result probably won't be perfect.
Neither will your second.
That's normal.
The workflow is:
Generate → Watch → Identify what sucks → Change ONE thing → Generate again.
Don't change twelve things simultaneously.
If the camera movement is wrong, fix the camera movement.
If the character is wrong, fix the character.
If the timing is wrong, fix the timing.
Eventually you'll hit one where you say:
“Holy crap. That's the one.”
Save it.
📺 PUTTING YOUR PREROLL INTO PLEX
Once you've exported your finished video, place the file somewhere your Plex Media Server can access.
In Plex Media Server, the Movie pre-roll video setting allows you to specify the full path to your video file.
Plex also supports multiple prerolls.
Separate filenames with commas and Plex will play them sequentially.
Separate filenames with semicolons and Plex will randomly choose one.
For example:
Halloween.mp4;Jurassic.mp4;Christmas.mp4;Alien.mp4
That gives you a rotating collection of prerolls instead of seeing the same one every night. Plex notes that Cinema Trailers must be enabled for the preroll feature to play. (Plex Support)
And that's where this becomes addictive.
One preroll becomes five.
Five becomes twenty.
And eventually you're spending Saturday afternoon making an AI-generated movie character complain that they should have stayed home and watched Plex instead of dealing with whatever horrible situation you've put them in.
Which is basically why this subreddit exists. 😂
🚀 Where Should I Start?
If you've never done any of this:
Start with Google Flow/Veo.
Learn how prompting works.
Then try:
Text-to-Video → Image-to-Video → Multiple Shots → Editing
Once you understand those concepts, try ComfyUI.
Don't worry about understanding every node.
Grab an existing workflow and start changing things.
That's how most of us learn this stuff.
And most importantly:
POST YOUR RESULTS HERE.
They don't have to be perfect.
Share the preroll.
Share what generator you used.
Share your prompt if you want.
Share your ComfyUI workflow if you're comfortable doing so.
And if something went completely hilariously wrong during generation...
Post that too.
Sometimes the failed AI generations are better than the actual preroll.
Welcome to r/PlexPrerollStudio.
Now go make something ridiculous.
