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Document format

SMI converter

An .smi file is a SAMI caption document: HTML-like markup in which <SYNC Start=…> elements mark the millisecond at which a caption appears, and the caption runs until the next SYNC. Microsoft designed it as an accessibility format, so a single file can carry several languages selected by CSS class.

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Drop SMI files here

Batch files can each use a different output. Nothing uploads for local conversions.

Working inputs include camera RAW, browser-local audio/video, PDF, CBZ/CBR comics, office documents, ebooks, markup, 3D models, structured text, images, and archives.

Where SMI comes from

Microsoft introduced SAMI in the late 1990s for Windows Media Player, aiming at the accessibility requirements that were becoming mandatory for public-sector media. It spread widely in Korea and remained the default caption sidecar for Windows Media content for years before WebVTT and TTML took over on the web.

How SMI works

  • The document has an HTML shape: <SAMI> wrapping <HEAD> with a <STYLE> block and <BODY> with the SYNC elements.
  • Each <SYNC Start=milliseconds> begins a caption; a following SYNC whose paragraph is &nbsp; is the conventional way to clear it.
  • Language tracks are CSS classes on the <P> elements, so one file can hold several languages at once.
  • Being HTML-like, the format tolerates unclosed tags — parsers must be forgiving, and must never execute embedded script.

When to use SMI

  • Captioning legacy Windows Media and Silverlight content
  • Reading multi-language caption archives produced for accessibility compliance
  • Converting a SAMI archive into WebVTT for a modern web player
  • Recovering timed dialogue from Korean-language media archives, where SAMI stayed common

Strengths and limitations

Strengths

  • Several language tracks in one file, chosen by class
  • Plain text and editable anywhere
  • Still recognised by many desktop players

Limitations

  • Never formally standardised, so real-world files vary in structure
  • The HTML shape invites embedded markup that a naive parser may render or execute
  • End times are implied by the next SYNC rather than stated, which makes gaps ambiguous

Compatibility

Windows Media Player, VLC, PotPlayer, and MPC-HC read .smi, and Subtitle Edit converts it. Browsers do not. Novus Convert parses the SYNC blocks locally with document types and external entities refused and script and style content removed before any text is read, then writes any of the twelve timed-text targets.

Style-class and title information describes presentation and language selection, not the cues; conversion keeps timing and text.

Convert SMI to another format

Convert other formats to SMI