Convert a .sub subtitle file to STL in seconds—right in your browser for quick sharing and playback workflows.
Both ends of this conversion are ambiguous extensions, so it is worth being precise before anything else. The .sub this page reads is MicroDVD, the frame-numbered plain-text format from the DivX player era. The .stl it writes is the Spruce / DVD Studio Pro subtitle format — a plain-text timecode list — and not EBU Tech 3264, the binary broadcast format that shares the extension. If you were sent an STL request by a broadcaster, read the next section carefully; it is almost certainly the other one.
| Property | Spruce / DVD Studio Pro STL | EBU STL (Tech 3264) |
|---|---|---|
| Nature | Plain text, one subtitle per line | Binary |
| Structure | hh:mm:ss:ff , hh:mm:ss:ff , text |
A 1024-byte General Subtitle Information block followed by 128-byte Text and Timing Information blocks |
| Published | Spruce Technologies authoring tools; carried on into Apple DVD Studio Pro | EBU, 27 February 1991 |
| Timing | SMPTE-style timecode with a frame field | Timecode fields inside each TTI block |
| Readable in a text editor | Yes | No |
| Line break within a subtitle | | pipe character |
Encoded control codes |
| Typical users | DVD authoring, subtitle round-tripping between editors | Broadcast subtitle delivery and archives |
| Produced by this page | Yes | No |
If you genuinely need EBU Tech 3264, you need a tool that writes the binary GSI and TTI block structure — Subtitle Edit and broadcast authoring suites do this. Converting to Spruce STL and renaming it will not work, because the two files have nothing structurally in common.
Each cue becomes one line, with start timecode, end timecode and text separated by commas:
hh:mm:ss:ff, where the last field is a frame number rather than milliseconds — the same shape SubtitleEdit's DVD Studio Pro writer produces.| between the lines, matching MicroDVD's own separator.In practice: handed a cue running from 960 ms to 3,840 ms, this emitter writes 00:00:00:24 , 00:00:03:21 , Correctly timed — 960 ms being frame 24 at 25 fps, and 840 ms rounding to frame 21.
| Property | Value |
|---|---|
| Standard | None — de facto, from the MicroDVD player |
| Cue syntax | {startFrame}{endFrame}Text, one per line |
| Timing base | Frame numbers |
| Precision | One frame — 40 ms at 25 fps |
| Frame rate in the file | Only by convention, as a first line like {1}{1}23.976 |
| Line break | | pipe |
| Styling codes | {y:i} italic, {y:b} bold, {y:u} underline, {f:name} font, {s:n} size, {c:$BBGGRR} colour in blue-green-red order |
| Positioning | {P:x,y} |
| Encoding | Undeclared; legacy code pages are common |
Both formats are frame-flavoured, which makes this look like a natural pairing — but they do not share a frame rate, and neither one records the one it was authored against.
This is the conversion where frame rate bites twice. On the way in, MicroDVD's {1440}{1560} values are frame indices that only mean something once you know the video's frame rate; this converter assumes 25 fps and offers no control to change it. On the way out, the STL frame field is generated at a fixed 25 fps as well. Neither number is derived from your video.
The format's own convention — a first line reading {1}{1}23.976 — is not interpreted here. It matches the ordinary cue pattern and comes through as a subtitle whose text is the string 23.976, so strip it before converting or delete the first output line. For contrast, FFmpeg's MicroDVD reader does scan the first three lines for that declaration and falls back to 23.976 fps when it is absent.
Open the STL in your editor against the video before you commit to it. MicroDVD timing scale is an open defect on our side, so the timecodes are the part to verify; the text, line ordering and | breaks come through reliably.
No, and this is the most important thing on the page. EBU Tech 3264 is a binary format: one 1024-byte General Subtitle Information block followed by a run of 128-byte Text and Timing Information blocks. What this page writes is the Spruce / DVD Studio Pro text format, which you can open in Notepad. If a broadcaster asked for STL, they mean the EBU one, and you will need dedicated software such as Subtitle Edit to produce it.
25 fps, fixed. The frame field in each hh:mm:ss:ff timecode is computed from the cue's millisecond remainder at 25 fps, independent of the source and with no option to change it. On a 23.976 or 29.97 fps project the seconds will be in the right neighbourhood but the frame field will not line up with a real frame boundary on your timeline.
hh:mm:ss:ff instead of milliseconds?Because it comes from video authoring, where the meaningful unit of time is a frame rather than a thousandth of a second — a subtitle cannot change on a boundary that is not a frame boundary. That is also why the format needs a project frame rate to be interpreted correctly, in exactly the same way MicroDVD does.
No. MicroDVD's {y:i}, {y:b}, {c:$BBGGRR} and related codes are stripped along with their braces during parsing, and the Spruce STL line format has no styling field to receive them anyway. The output is plain text with timecodes.
With a pipe. A MicroDVD cue written {100}{200}Line one|Line two is parsed into a two-line cue and written back out as Line one|Line two in the STL, because both formats settled on | as their line separator. Editors that read Spruce STL split on it to rebuild the second display line.
That is the format's intended home — it is the DVD Studio Pro subtitle text format, and Subtitle Edit implements a reader and writer for it. Set the project frame rate in your editor to match your video when importing, since the file itself carries no frame-rate declaration for the editor to read.
No. This page runs its conversion entirely in your browser: the file is read locally, parsed and re-emitted by JavaScript on the page, and the download is generated in memory. There is no server-side copy at any point.
Very often, yes. SubRip carries absolute millisecond times, needs no frame rate to interpret, and is accepted by essentially every player and editor, which makes it the safer interchange choice unless a DVD authoring tool has specifically asked you for STL. SUB to SRT is the same conversion with SubRip as the target.
Nothing in the input matched the {digits}{digits}text pattern. .sub is a badly overloaded extension: SubViewer files use timestamps rather than frames, and a .sub accompanied by an .idx is VobSub, which stores rendered pictures of the subtitles instead of text and needs OCR. A quick look in a text editor tells you which you have — MicroDVD is readable and full of curly braces.