Guides · 28 articles
Voice, captions and sound
Narration with real or synthetic voices, open text-to-speech models, word timing with Whisper, caption formats, and getting music and voice to sit well together.
AI Voice-Over for Videos: How to Get Natural Narration
AI voice-over uses text-to-speech software to turn a written script into spoken audio. A lifelike voice helps, but natural narration also depends on clear…
3 min readText-to-Speech for Videos: How to Choose a Voice Engine
When you make a narrated video, a text-to-speech voice engine turns your written script into spoken audio.
4 min readKokoro TTS: A Practical Guide to the Open Voice Model
If you need spoken narration for a project, Kokoro is an open-weight text-to-speech (TTS) model, software that turns written text into audio.
4 min readKokoro TTS Voices: The List and How to Pick One
When you use Kokoro to turn text into speech, your voice choice shapes how the narration sounds and whether it fits your audience.
3 min readBest Open Source Text-to-Speech Models: Kokoro, Piper, Chatterbox and More
For narration, accessibility, or product use, open text-to-speech (TTS) models let you generate speech without depending entirely on a commercial service.
3 min readOffline Text-to-Speech: Running a Voice Model on Your Own Computer
Offline text-to-speech (TTS) lets your computer read text aloud without sending it to a speech service. The voice model turns words into audio on your computer.
4 min readHow to Write a Voice-Over Script
A voice-over script contains the words a narrator speaks in a video or audio production. For video, it also needs to fit what viewers see and hear, such as…
4 min readSpeaking Rate: How Many Words per Minute for Voice-Over and Video
For general English voice-over, start at about 150 words per minute (WPM). Plan for 140–160 WPM. Adjust that range to the script and audience, then account…
3 min readWord-Level Timestamps with Whisper
For captions or visuals that follow each spoken word, sentence-level transcript timing is too broad.
3 min readfaster-whisper: Fast Local Transcription with Word Timestamps
For local transcription, faster-whisper runs OpenAI’s Whisper speech-recognition model on your computer and can return word-level timestamps.
3 min readForced Alignment: Matching Audio and Text Word by Word
Forced alignment is the process of matching the supplied text to the audio and assigning times to its words.
3 min readHow to Add Captions to a Video
If you already have camera footage, use your video host’s caption-upload or editing feature instead: explainroo does not edit existing footage.
2 min readClosed Captions vs. Subtitles: What's the Difference?
Closed captions show spoken words and meaningful sounds for viewers who are deaf or hard of hearing. Subtitles show dialogue, often in another language.
3 min readOpen Captions: What They Are and When to Burn Them In
When you publish a video, you can place captions directly on the image or add a separate caption track viewers can turn on or off.
3 min readSRT Files: What They Are and How to Make One
When you need subtitles for a video, an SRT file gives a player the caption text and the times each caption should appear.
3 min readWebVTT vs. SRT: Which Caption Format to Use
When you add captions to an online video, use the format your video player accepts. WebVTT supports caption positioning and styling in compatible web players.
3 min readWord-by-Word Animated Captions: How They Work
In a video with word-by-word animated captions, each spoken word lights up or changes style as the voice reaches it.
3 min readAudio Ducking: Lowering Music Under a Voice-Over
When narration and background music play at the same time, the music makes speech harder to understand.
3 min readLUFS for YouTube and Social Video: Loudness Targets Explained
For a narrated video, make sure the voice stays clear whether viewers listen on a phone or laptop, or through headphones, without startling them or getting…
4 min readHow to Sync Animation to Narration Word by Word
An explainer animation is easier to follow when each visual change appears on the word that introduces it.
4 min readHow to Fix Kokoro TTS Pronunciation of Names, Acronyms and URLs
When Kokoro text-to-speech reads a script aloud, it sometimes misreads names, turns an acronym into a word, or speaks a web address as a string of symbols.
3 min readHow to Do a Voice-Over and Add It to Your Video
A voice-over is narration recorded separately from the picture and placed over video. You can record your own voice, generate narration, or record directly…
4 min readA Free ElevenLabs Alternative for Video Narration: Local Voices with explainroo
For explainer videos and product demos, explainroo generates English narration and builds the video on your computer.
4 min readHow to Make Subtitles with Whisper (SRT and VTT)
Save the timed captions as an SRT or VTT file. SRT works with many video players and editors; VTT is commonly used in web video.
3 min readkokoro-js: Running Kokoro Text-to-Speech in Node.js
js, use kokoro-js, a JavaScript interface to Kokoro, an open-weight text-to-speech model. Text-to-speech, or TTS, means generating spoken audio from written…
3 min readWhisper Alternatives for Transcription and Word Timing
Choose a speech-to-text service by the timestamp detail you need. Some services timestamp segments; others mark the start and end of each word.
4 min readElevenLabs vs. Kokoro TTS for Video Narration
For video narration, ElevenLabs generates voices through a hosted service. ElevenLabs suits creators who want a managed service and built-in narration tools.
4 min readHow to Make a Video Transcript
A video transcript is a readable text version of a video's content. It includes spoken words and, when needed, sounds and visual details that help explain…
3 min readVideos made with explainroo
A coding agent made each of these with explainroo, from the script to the finished MP4.
- Vertical 9:16
- Clean look
How compound interest works
What happens to 1,000 dollars at 5 percent a year over 30 years, and why interest on interest adds up.
- Reels 9:16
- 1.1x pace
- Paper look
Why bread rises
How yeast makes gas, how kneaded gluten traps the bubbles, and how the oven sets the bread around them.
Free and open source
Make your own with your AI agent
explainroo lets a coding agent like Claude Code or Codex make narrated explainer videos and product demos. The voice, the word timing and the rendering run on your own computer, with no API key and no cost per video.
Copy this into your AI agent
Make me a short explainer video about [your topic]. Use explainroo for it: clone https://github.com/vincentsch/explainroo, read its AGENTS.md and follow the steps.
Made with explainroo: How compound interest works