Convert TTML to STL Online

How to Convert TTML to STL Online

1. Upload Your TTML File: Drag and drop your .ttml, .dfxp, or .xml file, or click "Add Files" to select. The page also accepts pasted XML directly. The whole conversion runs in your browser — your subtitles never leave your machine.
2. Confirm Output as STL: STL is preselected as the target. xconvert outputs the Spruce STL Text Script flavour — a plain-text format with $-prefixed configuration commands and HH:MM:SS:FF timecodes, the same dialect used by Apple DVD Studio Pro and Adobe Encore for DVD/NLE authoring.
3. Review TTML Timing (Optional): Preview the parsed cues to confirm timecodes, line breaks, and styling map cleanly. TTML's CSS-style positioning is approximated to STL's row-based layout (rows 1-23); colors and italics are preserved where the chosen character code table allows.
4. Convert and Download: Click Convert. You'll get a single .stl file ready to ingest into Cavena, EZTitles, Screen Subtitling, Avid, or your station's playout server. No upload, no watermark, no sign-up.

Why Convert TTML to STL?

TTML (Timed Text Markup Language) is the modern XML standard W3C finalized as TTML1 in November 2010 and TTML2 in November 2018; streaming services, Apple HLS, DVB, ATSC, and HbbTV all consume it. Spruce STL is the plain-text subtitle script format used by Apple DVD Studio Pro and Adobe Encore for DVD and Blu-ray authoring — and still accepted by NLE captioning suites like EZTitles and FAB Subtitler. If your subtitle was authored in a modern streaming-first XML workflow and now needs to slot into a DVD authoring project, an NLE round-trip, or a legacy post-production archive, STL is the input the authoring app expects.

• DVD and Blu-ray authoring — Apple DVD Studio Pro and Sonic Scenarist both import the Spruce STL script (.stl) as a subtitle stream. Convert your TTML master to STL to bring it into a physical-media authoring pipeline.
• NLE round-trips — EZTitles, Spot, and FAB Subtitler all read and write Spruce STL, making it a common interchange format when you're handing off a captioning project between vendors or workflows.
• Legacy post-production archives — Many post houses archived caption stems in the Spruce .stl script through the late 2000s; converting your TTML captions to that format lets you slot them next to existing assets in the same library.
• Strip XML overhead for editors — TTML's nested XML can be difficult for translators and proofreaders. STL's plain $-command + cue format is faster to hand-edit or spot-check in any text editor.
• Frame-accurate timing for disc authoring — DVD subtitles are scheduled against an HH:MM:SS:FF programme timecode, not a millisecond clock. Converting to STL realigns your cues to the frame grid that disc authoring tools schedule against.

TTML vs Spruce STL — Format Comparison

Property	TTML (.ttml / .dfxp / .xml)	Spruce STL (.stl)
Structure	XML, human-readable, CSS-style styling	Plain text: $-prefixed header commands + HH:MM:SS:FF cue lines
Standard body	W3C (TTML1 2010, TTML2 2018)	Spruce Technologies (no formal published standard; de facto reference is DVD Studio Pro documentation)
Profiles	EBU-TT, IMSC1/IMSC2, SMPTE-TT, DFXP, CFF-TT	N/A — single plain-text format; $DisplayStandard sets frame rate
Frame rate handling	Any rate via frameRate / tickRate attributes	$DisplayStandard directive: NTSC (29.97), NDF, or PAL (25 fps)
Character set	UTF-8 (full Unicode)	ANSI code pages or UTF-8/UTF-16 per exporter; global setting at file head
Styling	Full CSS subset: color, font, italic, bold, position, region	Global font/colour at file head; inline italic via ^I…^I tags
Typical caps	None imposed by spec (limits set by profile/player)	DVD Studio Pro render settings define visible rows and characters
Primary use	Streaming, OTT, archive masters, web players	DVD/Blu-ray authoring, NLE subtitle tracks, legacy post-production archives
Editing	Any text editor; XML schema validation	DVD Studio Pro, Adobe Encore, EZTitles, FAB Subtitler

Spruce STL Command Quick Reference

These are the $-prefixed directives at the top of every Spruce STL script. xconvert writes sensible defaults; open the output and tune any of them if your authoring tool expects different values.

Command	What it controls	Typical value
$DisplayStandard	Frame rate / TV standard for the timecode grid	NTSC (29.97 non-drop), NDF (drop frame), or PAL (25 fps)
$TapeOffset	Whether timecodes are tape-offset (True) or zero-based (False)	False for media-relative subtitles
$FontName	Global font family for all cues	Arial, Helvetica, or a font installed in the authoring app
$FontSize	Point size for the cue text	26–32 is typical for 720×480 NTSC
$HorzAlign / $VertAlign	Default horizontal / vertical alignment	Center / Bottom
$ColorIndex1…$ColorIndex4	The four-colour palette used for the subtitle bitmap on DVD	Tool-defined; DVD Studio Pro renders the script against these
^I … ^I	Inline italic open/close inside a cue line	Inserted automatically when xconvert detects tts:fontStyle="italic" in TTML

Frequently Asked Questions

Why would I use STL when my workflow is TTML / EBU-TT?

Spruce STL is not a broadcast standard — it's the subtitle script format for DVD/Blu-ray authoring tools (DVD Studio Pro, Adobe Encore) and NLE captioning suites (EZTitles, FAB Subtitler, Spot). Convert TTML to STL when your downstream is one of those tools or when you're slotting new captions alongside an existing archive stored in the Spruce format. For true broadcast delivery (EBU-style binary STL for linear TV playout), you need a different tool that outputs EBU Tech 3264 binary.

Which frame rate should I pick for the STL output?

The default is NTSC at 29.97 fps non-drop, which matches the most common North American DVD authoring profile. Open the output and change $DisplayStandard to PAL (25 fps) or FILM (24 fps) if your project is PAL or cinema. Quantisation error in the conversion is at most one half-frame (~17 ms at 29.97 fps), which is below the perceptual threshold for caption timing.

Will my TTML colors, italics, and positioning survive in STL?

Italics survive — xconvert wraps italic spans in ^I…^I tags so DVD Studio Pro renders them in italic. Bold, underline, and colour spans do not survive, because Spruce STL applies a single global font and style at the file head; you cannot vary it cue-by-cue in the script. Region blocks, tts:origin, tts:extent, and tts:textAlign cue settings are dropped — DVD subtitles place text via the authoring tool's render settings, not per-cue positioning.

Does the file use UTF-8 or an ANSI code page?

xconvert writes UTF-8 by default. Older builds of DVD Studio Pro and some legacy authoring tools default to interpreting the file as Windows-1252. If you see mojibake, re-save the file as the code page that matches your language (Windows-1253 for Greek, Windows-1251 for Cyrillic, Windows-1256 for Arabic) or, if your tool supports it, save as UTF-16 BOM. EZTitles' export panel documents this exact workflow.

What's the difference between Spruce STL, EBU STL, DFXP, and SBV — and when do I convert to which?

Spruce STL (what xconvert outputs here) is a plain-text DVD/NLE authoring format. EBU STL (EBU Tech 3264 / .stl) is an entirely different binary format used by European broadcasters for linear-TV subtitle delivery — it shares the .stl extension by historical accident. DFXP is the original Netflix-era TTML profile — XML, Unicode, rich styling. SBV is YouTube's plain-text format. Pick Spruce STL for DVD/NLE workflows; pick DFXP for OTT/streaming masters; pick SBV for direct YouTube upload. We also offer TTML to SRT and TTML to VTT for the most common SRT/WebVTT pipelines.

Can xconvert handle large series-level TTML files in batches?

Yes — drag-and-drop multiple .ttml files at once and each one outputs an independent .stl. Because conversion runs entirely in your browser there's no per-file size cap imposed by an upload service; the practical limit is your machine's available memory. We've seen feature-length TTML files (over 2,000 cues) convert in under a few seconds on a recent laptop. Nothing is uploaded to our servers.

I need to go the other direction — STL to TTML — can you do that?

Yes. Use STL to TTML to lift a legacy .stl from your broadcaster archive back to XML/TTML for streaming or web delivery. The reverse is common when a programme that was originally subtitled for linear TV gets a streaming re-release; the TTML output preserves timing and falls back to UTF-8, so Cyrillic/Greek/Arabic that was lost to a single-CCT STL can be re-added by hand.

Is the conversion really private?

Yes. Open the Network tab in your browser DevTools and you'll see zero subtitle bytes leaving your machine — the TTML→STL parser runs as compiled JavaScript locally. This matters when the script is under NDA (pre-release titles, embargoed news), when you're handling personally identifiable spoken content, or when broadcast-rights agreements forbid third-party cloud processing.