How do I tell EBU-STL from Spruce STL?

Open it in a text editor. Readable comma-separated lines are Spruce. A file starting with 850STL or 437STL and then unreadable bytes is EBU-STL.

Does Premiere Pro import Spruce STL?

No. Premiere’s STL import is the EBU binary format. Convert Spruce STL to SRT first.

Can I create an EBU-STL for a broadcaster from an SRT?

Yes. The SRT to EBU-STL converter writes a compliant file at 25 or 30 fps, with ISO 6937 text and a full GSI header.

Your .stl subtitle file won’t open, or imports as nothing

What you searched for

STL subtitle file won’t open or imports blank

Seen in: Premiere Pro, DaVinci Resolve, text editors

What is actually wrong

The extension .stl is used by two formats that have nothing in common. EBU-STL (Tech 3264) is a binary file with a 1024-byte header and fixed-size subtitle blocks; Premiere and Resolve import it. Spruce STL is a plain-text format from Apple’s DVD Studio Pro that those importers do not read. A Spruce file sent to an EBU importer, or the reverse, imports blank or is refused.

Fix it here: EBU-STL to SRT

Drop the file. It is detected and converted in your browser; nothing is uploaded. Free to start, no signup.

Convert a file now

Conversions …

Drop EDL, SRT, VTT, .prtranscript, or transcript files

Any caption, transcript or timeline file: CutConvert picks the converter and shows what survives · up to 100 KB per file

The fix, step by step

Open the file in a text editor
Readable lines like "00:00:04:00 , 00:00:07:12 , Welcome back" are Spruce STL. A file that starts with 850STL or 437STL followed by mostly unreadable bytes is EBU-STL.
Convert to SRT
Drop the file here. EBU-STL is decoded from its binary blocks, including the ISO 6937 accented characters, at the frame rate stored in the header. Spruce STL timecodes are converted to milliseconds.
Import the SRT, or re-encode as EBU-STL
SRT works everywhere. If a European broadcaster asked for STL, the SRT to EBU-STL converter writes a compliant binary file at 25 or 30 fps.

Two formats, one extension

EBU-STL is the European Broadcasting Union’s subtitle exchange format, specified in Tech 3264 in 1991 and still required by broadcasters across Europe and by many streaming deliverables. It is binary: a 1024-byte General Subtitle Information block with the code page, frame rate, programme title and counts, followed by 128-byte Text and Timing Information blocks, one per subtitle (or per part of a long subtitle). Text uses the ISO 6937 character set, where accented letters are written as a combining accent byte followed by the base letter. Timecodes are frame-based at 25 or 30 fps.

Spruce STL is a plain-text format that Spruce Technologies created for DVD authoring and that Apple carried into DVD Studio Pro. Each line is start , end , text, with timecodes and optional $ directives for font and position. It is readable in any editor and was never a broadcast format.

They share nothing but three letters. Software that imports one does not import the other.

Which importers read which

Premiere Pro’s caption import lists "EBU STL" and reads the binary format only. DaVinci Resolve likewise. Subtitle Edit and a few caption tools read both. YouTube reads neither. If a Spruce file goes into Premiere, the import fails or produces an empty caption track; if an EBU file is opened in a text editor it looks like corruption.

What the conversion keeps

From EBU-STL: every subtitle’s text with accents correctly recombined, line breaks, italics where the file uses the control codes, and timing converted from frames at the header’s rate to milliseconds. Justification and box styling are dropped; SRT has no field for them.

From Spruce STL: text and timing. The $ styling directives are dropped.

To EBU-STL, from SRT: a header with the programme title, the frame rate you choose, and correctly encoded ISO 6937 text, verified against a reference decoder. Overlong subtitles are split across blocks as the specification requires.

Nothing uploaded

Both directions run in your browser. Broadcast subtitle files describe programmes before transmission, and they stay on your machine here.

FAQ

How do I tell EBU-STL from Spruce STL?: Open it in a text editor. Readable comma-separated lines are Spruce. A file starting with 850STL or 437STL and then unreadable bytes is EBU-STL.
Does Premiere Pro import Spruce STL?: No. Premiere’s STL import is the EBU binary format. Convert Spruce STL to SRT first.
Can I create an EBU-STL for a broadcaster from an SRT?: Yes. The SRT to EBU-STL converter writes a compliant file at 25 or 30 fps, with ISO 6937 text and a full GSI header.

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