Adding subtitles to video content is essential for expanding your audience, improving accessibility, and increasing reach on social media. However, manual subtitle creation is extremely time-consuming — creating subtitles for 1 minute of video takes 5-10 minutes, meaning a 30-minute video requires 2.5-5 hours of work.
This article explains how to auto-generate subtitle files (SRT/VTT) using AI transcription.
Subtitle File Basics
What Is SRT?
SRT (SubRip Text) is the most widely used subtitle format. It's supported by virtually all video platforms and editing software, including YouTube, Premiere Pro, and DaVinci Resolve.
1
00:00:01,000 --> 00:00:04,500
Hello, today's topic is
AI transcription.
2
00:00:05,000 --> 00:00:08,200
Let's start by explaining
the basic concepts.
What Is VTT?
VTT (WebVTT) is the web-standard subtitle format. It integrates directly with HTML <video> tags, making it ideal for displaying subtitles on website videos.
WEBVTT
00:00:01.000 --> 00:00:04.500
Hello, today's topic is
AI transcription.
00:00:05.000 --> 00:00:08.200
Let's start by explaining
the basic concepts.
When to Use SRT vs. VTT
| Use Case | Recommended Format |
|---|---|
| YouTube / Video editors | SRT |
| Website videos | VTT |
| General purpose | SRT (easy to convert to VTT) |
Auto-Generating Subtitles with AI
Method 1: Whisper Command Line
OpenAI Whisper can output SRT/VTT files directly from the command line:
# Generate SRT subtitles
whisper video.mp4 --model large-v3-turbo --language en --output_format srt
# Generate VTT subtitles
whisper video.mp4 --model large-v3-turbo --language en --output_format vtt
Method 2: GUI Tools
GUI tools let you generate subtitle files by simply dragging and dropping your video. WhisperApp allows you to export transcription results in SRT/VTT format with just a few clicks.
Method 3: faster-whisper for Speed
When processing speed matters, faster-whisper generates subtitles up to 4x faster than the original Whisper implementation.
Tips for Better Subtitle Quality
1. Choose the Right Model
Subtitle quality directly depends on transcription accuracy. We recommend using the large-v3-turbo or large-v3 model.
2. Adjust Timestamps
AI-generated subtitles may have slightly off timing. Fine-tune in your video editor or use WhisperApp's timestamp editing features.
3. Watch Line Length
Overly long subtitles crowd the screen. General guidelines:
- English: Up to 42 characters per line
- Japanese: Up to 20 characters per line
- Display time: 1-7 seconds per subtitle
4. Check Proper Nouns
AI transcription tends to misrecognize proper nouns (names, product names, technical terms). Always review and correct after generation.
Uploading Subtitles by Platform
YouTube
- Log in to YouTube Studio
- Select the video → "Subtitles" tab
- "Add subtitles" → "Upload file"
- Select and upload your SRT file
Vimeo
- Open the video settings
- In the "Subtitles" section, click "Upload file"
- Select your SRT or VTT file
Your Own Website
Use HTML5 <video> and <track> tags to display subtitles:
<video controls>
<source src="video.mp4" type="video/mp4">
<track src="subtitles.vtt" kind="subtitles" srclang="en" label="English" default>
<track src="subtitles-ja.vtt" kind="subtitles" srclang="ja" label="Japanese">
</video>
Creating Multilingual Subtitles
For global video distribution, multilingual subtitles are essential. Since Whisper supports 99 languages, it's excellent for generating source text for translation.
Multilingual subtitle workflow:
- Auto-generate subtitles in the source language (SRT format)
- Translate to other languages using an LLM
- Save translated text in SRT format
- Upload each language's subtitle file to your video
With WhisperApp's LLM integration, you can complete the transcription-to-translation workflow within a single application.
Conclusion
AI transcription can reduce subtitle creation from hours of manual work to just minutes.
Auto-generating SRT/VTT files is a major productivity boost for YouTubers, video creators, and corporate video production teams. By choosing an accurate model and reviewing the output, you can efficiently produce professional-quality subtitles.
