Dub YouTube with Voice.ai

Dub YouTube videos with Voice.ai TTS. Turn scripts into publish-ready voiceovers with chapters, captions, and audio replacement for YouTube long-form and Shorts.

This skill follows the Agent Skills specification.

Turn any script into a YouTube-ready voiceover — complete with numbered segments, a stitched master, chapter timestamps, SRT captions, and a review page. Drop the voiceover onto an existing video to dub it in one command.

Built for YouTube creators who want studio-quality narration without the studio. Powered by Voice.ai.

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When to use this skill

Scenario	Why it fits
YouTube long-form	Full narration with chapter markers and captions
YouTube Shorts	Quick hooks with punchy delivery
Course content	Professional narration for educational videos
Screen recordings	Dub a screencast with clean AI voiceover
Quick iteration	Smart caching — edit one section, only that segment re-renders
Batch production	Same voice, consistent quality across every video

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The one-command workflow

Have a script and a video? Dub it in one shot:

bash

node voiceai-vo.cjs build \
  --input my-script.md \
  --voice oliver \
  --title "My YouTube Video" \
  --video ./my-recording.mp4 \
  --mux \
  --template youtube

This renders the voiceover, stitches the master audio, and drops it onto your video — all in one command. Output:

• out/my-youtube-video/muxed.mp4 — your video dubbed with the AI voiceover
• out/my-youtube-video/master.wav — the standalone audio
• out/my-youtube-video/review.html — listen and review each segment
• out/my-youtube-video/chapters.txt — paste directly into your YouTube description
• out/my-youtube-video/captions.srt — upload to YouTube as subtitles
• out/my-youtube-video/description.txt — ready-made YouTube description with chapters

Use --sync pad if the audio is shorter than the video, or --sync trim to cut it to match.

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Requirements

• Node.js 20+ — runtime (no npm install needed — the CLI is a single bundled file)
• VOICE_AI_API_KEY — set as environment variable or in a .env file in the skill root. Get a key at voice.ai/dashboard.
• ffmpeg (optional) — needed for master stitching, MP3 encoding, loudness normalization, and video dubbing. The pipeline still produces individual segments, the review page, chapters, and captions without it.

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Configuration

Set VOICE_AI_API_KEY as an environment variable before running:

bash

export VOICE_AI_API_KEY=your-key-here

The skill does not read .env files or access any files for credentials — only the environment variable.

Use --mock on any command to run the full pipeline without an API key (produces placeholder audio).

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Commands

build — Generate a YouTube voiceover from a script

bash

node voiceai-vo.cjs build \
  --input <script.md or script.txt> \
  --voice <voice-alias-or-uuid> \
  --title "My YouTube Video" \
  [--template youtube] \
  [--video input.mp4 --mux --sync shortest] \
  [--force] [--mock]

What it does:

1. Reads the script and splits it into segments (by ## headings for .md, or by sentence boundaries for .txt)
2. Optionally prepends/appends YouTube intro/outro segments
3. Renders each segment via Voice.ai TTS
4. Stitches a master audio file (if ffmpeg is available)
5. Generates YouTube chapters, SRT captions, a review page, and a ready-made description
6. Optionally dubs your video with the voiceover

Full options:

Option	Description
-i, --input <path>	Script file (.txt or .md) — required
-v, --voice <id>	Voice alias or UUID — required
-t, --title <title>	Video title (defaults to filename)
--template youtube	Auto-inject YouTube intro/outro
--mode <mode>	headings or auto (default: headings for .md)
--max-chars <n>	Max characters per auto-chunk (default: 1500)
--language <code>	Language code (default: en)
--video <path>	Input video to dub
--mux	Enable video dubbing (requires --video)
--sync <policy>	shortest, pad, or trim (default: shortest)
--force	Re-render all segments (ignore cache)
--mock	Mock mode — no API calls, placeholder audio
-o, --out <dir>	Custom output directory

replace-audio — Dub an existing video

bash

node voiceai-vo.cjs replace-audio \
  --video ./my-video.mp4 \
  --audio ./out/my-video/master.wav \
  [--out ./out/my-video/dubbed.mp4] \
  [--sync shortest|pad|trim]

Requires ffmpeg. If not installed, generates helper shell/PowerShell scripts instead.

Sync policy	Behavior
shortest (default)	Output ends when the shorter track ends
pad	Pad audio with silence to match video duration
trim	Trim audio to match video duration

Video stream is copied without re-encoding (-c:v copy). Audio is encoded as AAC for YouTube compatibility.

Privacy: Video processing is entirely local. Only script text is sent to Voice.ai for TTS. Your video files never leave your machine.

voices — List available voices

bash

node voiceai-vo.cjs voices [--limit 20] [--query "deep"] [--mock]

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Available voices

Use short aliases or full UUIDs with --voice:

Alias	Voice	Gender	Best for YouTube
ellie	Ellie	F	Vlogs, lifestyle, social content
oliver	Oliver	M	Tutorials, narration, explainers
lilith	Lilith	F	ASMR, calm walkthroughs
smooth	Smooth Calm Voice	M	Documentaries, long-form essays
corpse	Corpse Husband	M	Gaming, entertainment
skadi	Skadi	F	Anime, character content
zhongli	Zhongli	M	Gaming, dramatic intros
flora	Flora	F	Kids content, upbeat videos
chief	Master Chief	M	Gaming, action trailers

The voices command also returns any additional voices available on the API. Voice list is cached for 10 minutes.

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Build outputs

After a build, the output directory contains everything you need to publish on YouTube:

text

out/<title-slug>/
  segments/           # Numbered WAV files (001-intro.wav, 002-section.wav, …)
  master.wav          # Stitched voiceover (requires ffmpeg)
  master.mp3          # MP3 for upload (requires ffmpeg)
  muxed.mp4           # Dubbed video (if --video --mux used)
  chapters.txt        # Paste into YouTube description
  captions.srt        # Upload as YouTube subtitles
  description.txt     # Ready-made YouTube description with chapters
  review.html         # Interactive review page with audio players
  manifest.json       # Build metadata: voice, template, segment list
  timeline.json       # Segment durations and start times

YouTube workflow

1. Run the build command
2. Upload muxed.mp4 (or your original video + master.mp3 as audio)
3. Paste chapters.txt content into your YouTube description
4. Upload captions.srt as subtitles in YouTube Studio
5. Done — professional narration, chapters, and captions in minutes

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YouTube template

Use --template youtube to auto-inject a branded intro and outro:

Segment	Source file
Intro (prepended)	templates/youtube_intro.txt
Outro (appended)	templates/youtube_outro.txt

Edit the files in templates/ to customize your channel's branding.

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Caching

Segments are cached by a hash of: text content + voice ID + language.

• Unchanged segments are skipped on rebuild — fast iteration
• Modified segments are re-rendered automatically
• Use --force to re-render everything
• Cache manifest is stored in segments/.cache.json

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Multilingual dubbing

Voice.ai supports 11 languages — dub your YouTube videos for global audiences:

en, es, fr, de, it, pt, pl, ru, nl, sv, ca

bash

node voiceai-vo.cjs build \
  --input script-spanish.md \
  --voice ellie \
  --title "Mi Video" \
  --language es \
  --video ./my-video.mp4 \
  --mux

The pipeline auto-selects the multilingual TTS model for non-English languages.

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Troubleshooting

Issue	Solution
ffmpeg missing	Pipeline still works — you get segments, review page, chapters, captions. Install ffmpeg for stitching and video dubbing.
Rate limits (429)	Segments render sequentially, which stays under most limits. Wait and retry.
Insufficient credits (402)	Top up at voice.ai/dashboard. Cached segments won't re-use credits on retry.
Long scripts	Caching makes rebuilds fast. Text over 490 chars per segment is automatically split across API calls.
Windows paths	Wrap paths with spaces in quotes: --input "C:\My Scripts\script.md"

See references/TROUBLESHOOTING.md for more.

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References

• Agent Skills Specification
• Voice.ai
• references/VOICEAI_API.md — API endpoints, audio formats, models
• references/TROUBLESHOOTING.md — Common issues and fixes