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AgentCompany/builtin-skills/Video-maker/remotion-best-practices/rules/voiceover.md
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ZacharyZhang-NY e74dafcd36 Silence render-disposed spam, unbreak bundled skills, drop board wake
Three independently ugly bugs that all fed the same log flood:

* Electron's `WebFrameMain.send` writes every "Render frame was disposed"
  to stderr via `console.error`. When the worker fans a second
  agent-event past a reloading renderer, we produced thousands of
  identical lines and stalled the main loop on stderr I/O. Added a
  `mainFrame.detached` guard so the send is short-circuited before
  Electron's own catch block fires, and installed a targeted filter in
  `suppress-warnings.ts` (now actually imported from the entry point)
  so the specific `console.error("Error sending from webFrameMain:"…)`
  noise never reaches the terminal. Any other payload still surfaces.

* `dispatchAgentMessage` accepted the human-reader sentinel as a wake
  target when an agent replied to `__board__` — `wakeAgentIfPossible`
  then called `db.getAgent("__board__")`, threw, and the dispatcher
  kept repeating on every send. Strip `HUMAN_SENDER_ID` at
  `resolveMessageWakeTargets`, and keep a defense-in-depth guard in the
  heartbeat so a stray caller (future automation fan-out) cannot
  reintroduce the crash.

* Pi's skills loader rejects any SKILL.md whose frontmatter `name`
  diverges from its parent directory. The four bundled `my-writing-style`
  copies declared `name: writing-style-skill`, so every install emitted
  a warning and dropped the skill. They also lived as orphan gitlinks
  (mode 160000 without .gitmodules), and the global `*.md` gitignore
  hid every other SKILL.md from version control. Fixed the frontmatter
  to match the dir, converted the dangling submodules to plain trees,
  and allowlisted `builtin-skills/**/*.md` so a fresh clone carries the
  catalogue instead of silently losing it.
2026-04-20 08:13:48 -04:00

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---
name: voiceover
description: Adding AI-generated voiceover to Remotion compositions using TTS
metadata:
tags: voiceover, audio, elevenlabs, tts, speech, calculateMetadata, dynamic duration
---
# Adding AI voiceover to a Remotion composition
Use ElevenLabs TTS to generate speech audio per scene, then use [`calculateMetadata`](./calculate-metadata) to dynamically size the composition to match the audio.
## Prerequisites
By default this guide uses **ElevenLabs** as the TTS provider (`ELEVENLABS_API_KEY` environment variable). Users may substitute any TTS service that can produce an audio file.
If the user has not specified a TTS provider, recommend ElevenLabs and ask for their API key.
Ensure the environment variable is available when running the generation script:
```bash
node --strip-types generate-voiceover.ts
```
## Generating audio with ElevenLabs
Create a script that reads the config, calls the ElevenLabs API for each scene, and writes MP3 files to the `public/` directory so Remotion can access them via `staticFile()`.
The core API call for a single scene:
```ts title="generate-voiceover.ts"
const response = await fetch(
`https://api.elevenlabs.io/v1/text-to-speech/${voiceId}`,
{
method: "POST",
headers: {
"xi-api-key": process.env.ELEVENLABS_API_KEY!,
"Content-Type": "application/json",
Accept: "audio/mpeg",
},
body: JSON.stringify({
text: "Welcome to the show.",
model_id: "eleven_multilingual_v2",
voice_settings: {
stability: 0.5,
similarity_boost: 0.75,
style: 0.3,
},
}),
},
);
const audioBuffer = Buffer.from(await response.arrayBuffer());
writeFileSync(`public/voiceover/${compositionId}/${scene.id}.mp3`, audioBuffer);
```
## Dynamic composition duration with calculateMetadata
Use [`calculateMetadata`](./calculate-metadata.md) to measure the [audio durations](./get-audio-duration.md) and set the composition length accordingly.
```tsx
import { CalculateMetadataFunction, staticFile } from "remotion";
import { getAudioDuration } from "./get-audio-duration";
const FPS = 30;
const SCENE_AUDIO_FILES = [
"voiceover/my-comp/scene-01-intro.mp3",
"voiceover/my-comp/scene-02-main.mp3",
"voiceover/my-comp/scene-03-outro.mp3",
];
export const calculateMetadata: CalculateMetadataFunction<Props> = async ({
props,
}) => {
const durations = await Promise.all(
SCENE_AUDIO_FILES.map((file) => getAudioDuration(staticFile(file))),
);
const sceneDurations = durations.map((durationInSeconds) => {
return durationInSeconds * FPS;
});
return {
durationInFrames: Math.ceil(sceneDurations.reduce((sum, d) => sum + d, 0)),
};
};
```
The computed `sceneDurations` are passed into the component via a `voiceover` prop so the component knows how long each scene should be.
If the composition uses [`<TransitionSeries>`](./transitions.md), subtract the overlap from total duration: [./transitions.md#calculating-total-composition-duration](./transitions.md#calculating-total-composition-duration)
## Rendering audio in the component
See [audio.md](./audio.md) for more information on how to render audio in the component.
## Delaying audio start
See [audio.md#delaying](./audio.md#delaying) for more information on how to delay the audio start.