STL to SMI Subtitle Converter
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100% local processing in your browser. No upload. No waiting.
Drag & drop your STL file here
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Supports .stl files up to 50 MB
More Subtitle Tools
How It Works
Upload STL File
Drag & drop or select your .stl file
Convert Instantly
We process it locally in your browser
Download SMI
Get your .smi file immediately
Why Choose AllSubConverter?
Your Privacy Matters
Everything runs in your browser. Your files are never uploaded.
Lightning Fast
Optimized processing engine converts files in seconds.
Free & Local
Each file can be up to 50 MB. Batches can contain up to 200 files or 1 GB total.
Works Everywhere
Works on Windows, Mac, Linux, iOS, Android - any modern browser.
Free Online STL to SMI Converter
Our STL to SMI converter reads Spruce Subtitle text input and produces a single-language Synchronized Accessible Media Interchange document entirely in your browser. Source STL timing is converted to SMI millisecond Start attributes. Bracketed inline tags are removed, pipe separators become newlines, HTML special characters are escaped, and blank SYNC elements mark cue ends. The conversion runs client-side, so your subtitle files are never uploaded to a server.
Input Format
STLSTL (Spruce Subtitle) is a text-based subtitle format used in DVD authoring and some broadcast workflows. Each entry uses comma-separated start and end timecodes followed by the subtitle text, with the pipe character (|) denoting line breaks. This text STL variant is distinct from the binary EBU STL broadcast format.
Output Format
SMISMI (SAMI, Synchronized Accessible Media Interchange) is a Microsoft subtitle format using HTML-like <SYNC> elements with Start times in milliseconds. SMI supports multiple language tracks through CSS classes and is suitable for Windows Media Player and legacy accessibility workflows.
Features
Why Convert?
Format Differences
Common Use Cases
Windows Media Captions
Produce SMI captions for Windows Media Player and Microsoft-based playback environments.
Accessibility
Deliver SAMI accessibility captions for legacy corporate and educational media systems.
Multi-Language Files
Create a single-language SMI track that you can extend in SAMI-aware tooling if multiple classes are required.
Related Formats
SRT (SubRip)
The universal plain-text alternative: convert to SRT for maximum device compatibility.
VTT (WebVTT)
The web alternative: convert to VTT if your target is HTML5 video or YouTube.
TTML (Timed Text Markup Language)
The structured XML alternative: convert to TTML when a basic timed-text document is more suitable.
Frequently Asked Questions
It reads a Spruce Subtitle text file, parses each cue's timing and text, and writes a single-language SAMI document with an ENCC class, timed SYNC elements, escaped HTML text, and blank end markers. Source STL timing is converted to SMI milliseconds.
Absolutely. Every conversion runs client-side in your browser. No subtitle data, file contents, or metadata is ever transmitted to a server.
Yes. Bracketed STL tags are removed, pipe separators become <br> line breaks, and HTML special characters are escaped. Timing is converted to SMI milliseconds.
Yes, completely free with no sign-up, no watermarks, and files up to 50 MB each. All processing happens in your browser, so your files are never uploaded to a server.
Source STL timing (SMPTE HH:MM:SS:FF frame timecodes) is converted to SMI timing (whole milliseconds (Start=...)).
Yes. The responsive page works in modern mobile browsers.