Auto SFX
AI-Synchronized Sound Effects for Video

How does auto SFX sync sound to the picture?

That frame-aware approach is what separates a real auto SFX pass from generic royalty-free clips you would otherwise have to nudge into place by hand. Because the model is watching the picture, the timing comes out aligned on the first try for most clips, and you skip the tedious part of sound editing — scrubbing the timeline to line up every hit. You still keep control: pick the SFX duration (up to 10 seconds per generation) and, for longer videos, slide the start offset so the sound window lands exactly on the beat you want to score.

If you leave the prompt blank, auto-detection reads the footage and chooses the sounds itself. Add a short prompt — for example "gravel footsteps and distant wind" or "cinematic sci-fi impacts" — when you want to steer the palette toward a specific mood or override what auto-detection would otherwise guess.

How much does Auto SFX cost in credits?

Auto SFX is priced by the length of the sound-effects track: 10 credits for every 5 seconds, rounded up to the next block. A default 10-second pass is 20 credits, and every generation returns 2 variations — so you pay once and get two takes to compare. Short impacts under 5 seconds are the cheapest at 10 credits. Credits are shared across every Imagera tool.

Because each generation caps at 10 seconds of SFX, scoring a longer edit means running the tool a few times — once per moment you want to hit — and dropping the results into your editor. The start-offset control (up to 60 seconds into the clip) lets you position the 10-second window on the exact section you are scoring, so you are never paying to generate sound over footage you do not need.

Auto SFX vs. manual sound design and stock libraries

The traditional ways to add sound to a video are hiring a sound designer, or buying royalty-free clips and lining each one up by hand. Both work, but both cost time or money that a short social clip rarely justifies. Auto SFX trades a little fine control for speed: it watches the picture and places timed sound in seconds, letting you finish a clip in one pass instead of an afternoon.

For a hero cut where every hit needs to be perfect, a human sound designer still wins on nuance. For the everyday reality — dozens of reels, product clips and AI-generated shots that all need to feel finished this week — an auto SFX pass gets you 90% of the way in a fraction of the time, and you can always take the exported audio into your editor for the final polish.

What can you use video-to-SFX for?

Auto SFX earns its keep anywhere a clip has visible action to score. Below are the situations where a video-to-SFX pass makes the biggest difference — each one is about giving on-screen motion the sound it is missing, not adding a music bed or dialogue.

How do I build a full soundtrack, not just SFX?

Auto SFX generates sound effects only — foley, impacts, ambience and texture — deliberately kept separate from music and voice so you can balance each layer on its own. To assemble a complete mix, generate the SFX here, then add the other layers from the tools built for them and combine everything in your editor.

• Sound effects — this page. Timed foley and impacts synced to the picture.
• A music track — generate an original score with Music Factory, then set it under your SFX.
• Narration or dialogue — add a voiceover with the Voice Generator for explainers and ads.
• The picture itself — if your clip is still silent because it came from AI, make it in the Video Generator first, then bring it here to score.

For a deeper walkthrough with example clips, see the guide on AI sound effects for video.

How do I get the best sync from Auto SFX?

The sync quality of an auto SFX pass depends more on the clip you feed it than on the settings. The model scores what it can see, so footage with clear, isolated on-screen action gives it obvious events to hit. A few practical habits — choosing the right window length, using the offset on longer clips, and steering with a short prompt only when you need to — get you clean, aligned results on the first or second run.

Because generation only takes seconds, treat it as iterative: run a pass, watch it against the picture, adjust the duration or prompt, and run again. That loop is far faster than hand-placing library clips, and it is how most people dial in a reel's sound in a couple of minutes rather than an afternoon.

What formats, limits and controls does Auto SFX support?

Auto SFX runs entirely in the browser and accepts the common video formats you already export from your editor or capture from a phone. The table below is the honest spec — the exact formats, size and duration limits, and the controls you get in the studio — so you know what to expect before you upload.

If your clip is larger than 100MB or longer than you want to score in one pass, trim it in your editor first and upload the section you care about. For videos that came out of an AI model without any audio at all, generate the picture in the Video Generator and bring the result straight here to add its sound.

Can I use the generated sound effects commercially?

Yes. Sound effects you generate on a paid plan come with commercial rights, so you can use them in client work, monetized videos, ads and social content. The two variations you receive per run are both yours to keep — download the one you want, or export both and blend them in your editor. There are no per-clip licensing fees on top of the credits you already spent.

A practical point that trips people up with a video-to-SFX tool: the output is a sound layer for your clip, not a replacement editor. Auto SFX gives you timed effects synced to the picture; you then bring that audio into whatever timeline you already use to set levels against music and voice, add a fade, or trim the tail. Keeping the SFX as its own layer is what lets you mix it properly rather than being locked into a single baked-in balance.

If you generate a lot of clips, the credit-per-5-seconds model scales predictably: a batch of ten short reels scored at 10 seconds each is a known, flat credit cost, and every one of them arrives with two takes to choose from. That predictability is the reason teams reach for an auto SFX pass on volume work instead of licensing library clips one at a time.

Why is Auto SFX the missing step for AI-generated videos?

The workflow is short. Generate or upscale your clip, upload it here, optionally add a one-line prompt to steer the palette, and run a pass — you get two synced variations in seconds. Because the sync is driven by the picture rather than a caption, you do not need to know sound design; the model places events where the motion is. That makes it practical to give an entire batch of AI clips their audio in the time it used to take to score a single one by hand.

It pairs naturally with the rest of an AI video pipeline. Build the shot in the Video Generator, score it here, add a track from Music Factory and, if it needs a voice, drop narration in from the Voice Generator. Each tool draws from the same credit balance, so a full picture-plus-sound clip stays a few generations, not a full production.

More questions about Auto SFX

See it in action

Foley and sound-design scenes that show the kind of sonic detail auto-SFX adds to your footage.