TTML to SMI
Or paste subtitle text
What this conversion changes
2 things are dropped or need a decision
- Styling
all styling except bold and italic (colour, outline, shadow, margins)
- Format-specific content
content the source format keeps outside its cues (non-cue blocks, header text, per-cue settings, commented-out events) — the target format has no place for it
This list comes from the capability matrix for these two formats, not from the particular file you loaded. A specific file may lose more if it uses features the format allows but the matrix does not model.
This page converts TTML to SMI. Drop a file in — or paste the text — and you get the SMI version back. The conversion runs entirely in your browser, so nothing is uploaded and no account is needed.
These two formats do not store the same things, and the difference is not cosmetic: styling and format-specific content have nowhere to go in SMI. The list above comes from what the two formats can each express rather than from your file, so it is the same answer before you load anything.
One file is fine, and so is a whole season: the queue works through them in order and the results come down together as a single ZIP.
Examples
A typical TTML file, converted to SMI
Input
<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml" xmlns:tts="http://www.w3.org/ns/ttml#styling" xml:lang="en">
<head>
<styling>
<style xml:id="s1" tts:color="#FFFF00" tts:fontWeight="bold"/>
</styling>
<layout>
<region xml:id="bottom" tts:origin="10% 80%" tts:extent="80% 20%"/>
</layout>
</head>
<body>
<div>
<p begin="00:00:01.000" end="00:00:03.500" region="bottom" style="s1">Hello <span tts:fontStyle="italic">there</span>.</p>
<p begin="00:00:03.500" end="00:00:06.000" region="bottom">How are you?<br/>Fine, thanks.</p>
</div>
</body>
</tt>
Output
<SAMI>
<HEAD>
<STYLE TYPE="text/css">
<!--
P { text-align: center; font-family: Arial, sans-serif; }
-->
</STYLE>
</HEAD>
<BODY>
<SYNC Start=1000>
<P>Hello <i>there</i>.
<SYNC Start=3500>
<P>
<SYNC Start=3500>
<P>How are you?<br>Fine, thanks.
<SYNC Start=6000>
<P>
</BODY>
</SAMI>
Dropped in this output: styling and format-specific content. Everything else matches line for line.
The same conversion on an awkward input
Input
<?xml version="1.0" encoding="UTF-8"?>
<tt xmlns="http://www.w3.org/ns/ttml" xmlns:tts="http://www.w3.org/ns/ttml#styling"
xmlns:ttp="http://www.w3.org/ns/ttml#parameter"
ttp:frameRate="25" xml:lang="en">
<body>
<div>
<p begin="1.5s" dur="2s">Loaded from an offset and a duration.</p>
<p begin="4s" end="00:00:06.50">A coarser clock spelling.</p>
<p begin="00:00:07:00" end="00:00:08:12">Frames, at 25fps.</p>
<p begin="9s"><span tts:color="#FF0000">Half-open</span> and Tom & Jerry.</p>
</div>
</body>
</tt>
Output
<SAMI>
<HEAD>
<STYLE TYPE="text/css">
<!--
P { text-align: center; font-family: Arial, sans-serif; }
-->
</STYLE>
</HEAD>
<BODY>
<SYNC Start=1500>
<P>Loaded from an offset and a duration.
<SYNC Start=3500>
<P>
<SYNC Start=4000>
<P>A coarser clock spelling.
<SYNC Start=6500>
<P>
<SYNC Start=7000>
<P>Frames, at 25fps.
<SYNC Start=8480>
<P>
<SYNC Start=9000>
<P><font color="#FF0000">Half-open</font> and Tom & Jerry.
<SYNC Start=11000>
<P>
</BODY>
</SAMI>
This is the kind of damage real files have — mixed line endings, stray whitespace, fields left empty. Compare it with the tidy example above to see what the parser forgives.
Frequently asked questions
Which styling survives from TTML into SMI?
Emphasis, written into the text as tags: bold, italic, underline and a colour come out as `<b>`, `<i>`, `<u>` and `<font color="…">`, which browsers act on. What the SMI file will not carry is the style table TTML relies on — the font, its size, the outline, the shadow and the margins all go, and the page embedding the subtitles styles them from its own CSS instead.
What happens to the TTML prolog, its `<styling>` and `<layout>` tables in SMI?
Dropped. A TTML file keeps its look and its layout in the head rather than in the words: the XML declaration and its namespace bindings, the `<styling>` table of named styles (`tts:color`, `tts:fontWeight`), the `<layout>` table of named regions (`tts:origin`, `tts:extent`), any `<metadata>`, and the `style` / `region` attributes a `<p>` uses to point at them. SMI stores cues, not a document, so nothing in that head has a place to land. Styling written *inside* a paragraph is a different matter — a `<span tts:fontStyle="italic">` is emphasis on the words, and it is written out in SMI's own markup wherever SMI has any.
What does the output look like when TTML becomes SMI?
Like SMI: no cue numbers and no timecode line: every cue is a `<SYNC Start=…>` tag with its text in a `<P>` under it, and — because a SYNC replaces whatever was on screen — a `<P> ` block just after it that puts the screen back to empty. Every TTML cue becomes one SMI cue, in the same order, with the same text.
Are the TTML timings exact in the SMI file?
Yes, to the millisecond — which is as fine as either format goes. TTML writes a moment as `00:00:04.126` and SMI writes the same moment as `Start=4126`; nothing is rounded or shifted between the two, and a cue that was on screen for 2.9 seconds still is.
How does a two-line TTML cue come out in SMI?
As two lines with a `<br>` between them, which is how SAMI writes a hard line break. The pairing survives — the two TTML lines still belong to one subtitle in the SMI output, and a player shows them together.
Do TTML cues keep their order in the SMI output?
Yes, and they are sorted by start time on the way — earliest first, which is how every format here expects them and how players read them. If your TTML file listed its cues out of sequence, the SMI output puts them back in order; that is a change to the file's structure rather than its content, and it is deliberate.
Can I convert the SMI back to TTML?
Yes, and it has its own list: converting SMI to TTML drops format-specific content. That list is different from the one above because the two formats keep different things.
Does the SMI output keep the TTML file's encoding?
No — the output is UTF-8, with Unix line endings and no byte-order mark, whatever the TTML file used. A file that arrives in UTF-16, or in a Windows single-byte encoding, is decoded on the way in (the result panel says so when that happens); what comes out is always the same UTF-8 SMI.