What does the VTT to SMI converter preserve?

It preserves cue start and end timing, cue order, and cue text after line breaks are converted to elements and HTML special characters are escaped. VTT identifiers, settings, comments, and styling are not preserved.

Will the SMI output work on every Korean platform?

Check the platform's subtitle specification before upload. The converter generates a basic SAMI document and does not guarantee compatibility with a specific service.

Does the output include CSS styling?

It includes a STYLE block defining the default ENCC class. You can edit that CSS manually, but source VTT styling is not mapped into it.

Can I edit the SMI file after downloading?

Yes. SMI files are text documents and can be edited in a text editor. Validate timing, language classes, and text after manual changes.

What character encoding does the output use?

The generated text is written as UTF-8 content. The document does not include an explicit charset declaration, so encoding support depends on the target player or host configuration.

Is the VTT to SMI converter free?

Yes. It is free, requires no sign-up, adds no watermark, and accepts subtitle files up to 50 MB. Conversion runs locally in your browser.

Processing stays in your browser and the file is not uploaded to AllSubConverter. Browser storage, extensions, and enterprise device policies are controlled separately.

Can I use this on a phone?

Yes. The page can run in a modern mobile browser. Select a VTT file and download the resulting SMI file directly from the device.

How does VTT to SMI differ from SRT to SMI?

Both converters produce the same basic SAMI structure. The VTT parser accepts WebVTT timing and ignores VTT-specific identifiers and settings, while the SRT parser works from numbered SRT blocks.

Can I batch convert multiple VTT files to SMI?

Yes. Drop several valid VTT files on this page and they open in the workspace Batch tool with SMI preselected. The batch supports up to 200 files.

VTT to SMI Subtitle Converter

Turn timestamped WebVTT cues into a single-language SAMI document.

Drag & drop your VTT file here

or click to browse

Supports .vtt files up to 50 MB

Core Engine Architecture

About VTT to SMI

This browser-based converter reads timestamped WebVTT cue blocks and writes a basic SAMI (.smi) document. Cue start times become millisecond SYNC values, cue line breaks become <br> elements, HTML special characters are escaped, and a blank SYNC entry marks each cue end. The generated document contains one default ENCC language class rather than multiple language tracks.

Payload & Syntax Inspector

VTT to SMI Code Syntax & Structure Inspection

Side-by-side code inspection illustrating header definitions, timestamp syntax, and cue payload formatting

Millisecond Sync

input.vtt

VTT SOURCE

WEBVTT
 
00:00:01.000 --> 00:00:04.000
Hello, world!
 
00:00:04.500 --> 00:00:08.000
This is a subtitle file.
 
00:00:08.500 --> 00:00:12.000
Converted locally!

output.smi

SMI RESULT

<SAMI>
<BODY>
<SYNC Start=1000><P Class=ENCC>Hello, world!</P>
<SYNC Start=4000><P Class=ENCC>&nbsp;</P>
<SYNC Start=4500><P Class=ENCC>This is a subtitle file.</P>
<SYNC Start=8000><P Class=ENCC>&nbsp;</P>
<SYNC Start=8500><P Class=ENCC>Converted locally!</P>
<SYNC Start=12000><P Class=ENCC>&nbsp;</P>
</BODY>
</SAMI>

Specification Sheet

VTT vs SMI Technical Specifications

Standard Compliant

Input Format

VTT

VTT (WebVTT) is a text subtitle format for web video. A VTT file starts with a WEBVTT header and uses HH:MM:SS.mmm --> HH:MM:SS.mmm cue timing. It can also contain cue identifiers, cue settings, inline tags, NOTE blocks, and style metadata.

Output Format

SMI

SMI (SAMI, or Synchronized Accessible Media Interchange) is an HTML-based subtitle format. This converter generates a SAMI document with HEAD, STYLE, and BODY sections, one ENCC class, millisecond SYNC Start values, and a blank SYNC entry at each cue end.

Format Differences

VTT uses dot-separated timestamps; this SMI output uses millisecond SYNC Start values.

VTT is a web subtitle format; SMI is an HTML-based document format.

VTT cue settings and positioning are discarded during conversion.

VTT inline tags are escaped as literal text rather than becoming SAMI styling.

VTT comments and identifiers are not carried over.

This SMI output contains one default ENCC class, not multiple language tracks.

Conversion Troubleshooting & Gotchas

Practical solutions for player compatibility, character encoding, and timing synchronization

4 Common Gotchas

GOTCHA #1

Subtitle timing drifts or appears out of sync on media players

Video files frequently differ in framerate (e.g., 23.976 fps vs 25 fps). If the timing drifts steadily, use our Subtitle Sync tool to adjust the global offset or framerate stretch.

GOTCHA #2

Characters appear as garbled symbols or question marks (Mojibake)

Legacy files saved in Windows-1252, Shift-JIS, or GBK may render incorrectly. Our exporter standardizes output to clean UTF-8. Use our Subtitle Encoding Converter if the source file is corrupted.

GOTCHA #3

Overlapping captions when multiple speakers talk simultaneously

Different formats handle overlapping dialogue differently. If your target player cannot render stacked cues cleanly, open the file in our Subtitle Editor to adjust individual cue timings.

GOTCHA #4

Video editing software (Premiere, DaVinci, Final Cut) rejects the file

Professional NLE software enforces strict syntax rules. Our converter eliminates malformed line breaks and non-standard tags, producing clean, standardized files.

Features

Reads timestamped WebVTT cue blocks directly in your browser

Writes a complete single-language SAMI HTML document

Converts VTT start times to millisecond SYNC values

Converts cue line breaks to <br> elements

Escapes ampersands and angle brackets in caption text

Marks each cue end with a blank SYNC entry

Why Convert?

SAMI is still used by some Korean and legacy media workflows.

SAMI stores timing as millisecond offsets in an HTML document.

A basic SMI file can be edited in a text editor when a web caption needs to move to an older system.

Converting locally avoids uploading program material or caption text.

A single-language SAMI draft can be customized later with additional CSS or language classes.

Keeping VTT and SMI copies supports different playback environments.

Scenarios

Common Use Cases

Basic SAMI Draft

Create a basic single-language SAMI document from web subtitles before checking it in the target player or workflow.

Legacy Tool Interchange

Move timestamped VTT cues into a workflow that requests SAMI input rather than WebVTT.

Text Editing

Produce an HTML-based subtitle file that can be opened and edited in a standard text editor.

Local Conversion

Convert subtitles without uploading them to a separate conversion service.

Web and SAMI Copies

Keep a VTT version for web playback while producing a basic SMI copy for another environment.

Format Ecosystem

Related Formats

SRT

A simpler timestamped subtitle format that is widely supported by media players.

VTT

The readable web-video input format used by this converter.

ASS

A styled subtitle format for players and workflows that need detailed presentation controls.

How It Works

1
Select or drop a .vtt file; its contents stay on your device.
2
The parser finds timestamped cue blocks and reads their text.
3
Cue identifiers and settings are discarded.
4
Each start time is converted to a whole-millisecond SYNC Start value.
5
Line breaks become <br> elements and HTML special characters are escaped.
6
A blank SYNC entry is written at the cue end.

moreTools.fromFormat

VTT LRC VTT SRT VTT TXT VTT ASS VTT TTML VTT SCC VTT STL

moreTools.toFormat

SRT SMI ASS SMI LRC SMI SBV SMI SSA SMI TTML SMI SCC SMI STL SMI

More Subtitle Tools

Subtitle Format Cleaner

Remove formatting, tags and noise

Subtitle Editor

Edit subtitle content and timings

Subtitle Sync & Timing Calibration

Adjust timing with millisecond precision

Subtitle Merger

Combine multiple subtitle files

AI Subtitle Translator

Translate to 19 built-in target languages

Frequently Asked Questions

It preserves cue start and end timing, cue order, and cue text after line breaks are converted to <br> elements and HTML special characters are escaped. VTT identifiers, settings, comments, and styling are not preserved.

Tags such as italic, bold, class, and voice spans are not interpreted. Their angle brackets are escaped, so the source markup appears as literal text in the SAMI output.

Each cue start is written as a whole-millisecond SYNC Start value. The cue end is written as a second SYNC value containing a blank paragraph.

Cue settings such as line, position, align, and size are discarded. The output uses one default ENCC class and does not map VTT styling or positioning to SAMI CSS.

No. NOTE blocks do not contain caption text for this converter and are ignored. Only timestamped cue content is converted.

No. The converter writes one default ENCC class for English CC. Additional SAMI language classes can be added manually in a text editor, but this tool does not merge multiple VTT language files.

Ready to convert your subtitles?

Drop your VTT file here and convert to SMI instantly.

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Related Resources

What is VTT?What is SMI?VTT vs SMI ASS vs SMI LRC vs SMI SBV vs SMI