Can I convert SRT to STL for BBC delivery?

Yes. The BBC accepts STL format for subtitle delivery. The converter produces STL files with proper GSI headers and TTI blocks compatible with BBC subtitle delivery specifications.

What is the difference between STL and EBU-TT?

STL (Tech 3264) is a binary format used for older broadcast systems. EBU-TT is a newer XML-based format for modern broadcast workflows. STL is still widely used by European broadcasters, while EBU-TT is gaining adoption for newer systems.

How are TTI blocks structured in STL?

Each TTI (Text Timing Information) block is 128 bytes and contains a subtitle cue with extension block number, cumulative status, time in, time out, vertical position, justification, commentary flag, and text content. The converter generates properly structured TTI blocks for each SRT cue.

Can I edit the STL file after conversion?

STL files are binary and require specialized tools like EZTitles, Annotation Edit, or Poliscript to edit. You cannot edit them in a plain text editor like SRT files. For editable output, consider converting to TTML or VTT instead.

What happens to multi-line SRT cues in STL?

SRT cues with multiple lines are preserved in the STL TTI blocks. STL supports multi-row text within a single TTI block, and the converter maps SRT line breaks to STL row separators.

Are timestamps frame-accurate after STL conversion?

Yes. SRT millisecond timestamps are converted to frame-based STL timecodes. For 25 fps, each millisecond maps to approximately 0.025 frames. The converter rounds to the nearest frame, which may introduce up to 20ms of timing variance at 25fps.

Absolutely. All conversion happens client-side in your browser. No subtitle data, file contents, or metadata is ever transmitted to a server.

Can I batch convert multiple SRT files to STL?

This page converts one file at a time. For batch processing, use the Workspace feature to load multiple SRT files and convert them sequentially through the pipeline.

What file extension does STL use?

STL files use the .stl extension. The format is also sometimes referred to as EBU STL, Tech 3264, or simply broadcast subtitle format. The extension is recognized by broadcast subtitle tools and playout servers.

Does STL support italic and bold text?

STL supports a limited set of text styling through justification codes and character attribute flags in the TTI blocks. Italic can be encoded, but bold and other advanced styling from SRT files are typically simplified or stripped during conversion.

How large are STL files compared to SRT?

STL files are binary and typically larger than SRT files. A 50 KB SRT file may produce a 100-200 KB STL file because each TTI block is exactly 128 bytes regardless of the amount of text in the cue.

What countries use STL format?

STL is used across Europe by broadcasters in the UK (BBC, ITV), Germany (ARD, ZDF), France (France Televisions), Italy (RAI), Spain (TVE), Netherlands (NPO), and many other EBU member countries. It is the standard interchange format for European broadcast subtitles.

Can I use the STL output for DVD subtitles?

STL files are sometimes used as a source format for DVD subtitle authoring, but DVDs typically use a different binary subtitle format (SPU/VOBSUB). You may need additional conversion through a DVD authoring tool after generating the STL file.

SRT to STL Converter

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SRT

1
00:00:01,000 --> 00:00:04,000
Hello, world!
 
2
00:00:04,500 --> 00:00:08,000
This is a subtitle file.
 
3
00:00:08,500 --> 00:00:12,000
Converted locally!

STL

// Spruce Subtitle File
// Format: Start Time, End Time, Subtitle Text
 
00:00:01:00 , 00:00:04:00 , Hello, world!
00:00:04:15 , 00:00:08:00 , This is a subtitle file.
00:00:08:15 , 00:00:12:00 , Converted locally!

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Free Online SRT to STL Converter

Our SRT to STL converter transforms universal SubRip subtitles into EBU STL (Subtitle Transmission List) format for European broadcast television and DVD production. The converter generates a GSI header block with metadata fields, converts SRT millisecond timestamps to 25fps frame-based timecodes, maps subtitle text into TDI data blocks with proper field formatting, and produces a valid .stl file that European broadcasters and DVD authoring systems can ingest.

Input Format

SRT

SRT (SubRip) is the most universally supported subtitle format. Each entry has a sequential index number, a timestamp line in HH:MM:SS,mmm --> HH:MM:SS,mmm format (comma before milliseconds, arrow separating start and end), and subtitle text. SRT files are plain text and recognized by virtually every media player, smart TV, video editor, and streaming platform.

Output Format

STL

STL (EBU STL, Subtitle Transmission List) is a subtitle format standardized by the European Broadcasting Union (EBU Tech 3264) for television subtitling and DVD production. STL files contain a header block (GSI - General Subtitle Information) with metadata like program title, translator, revision, and frame rate, followed by subtitle data entries (TDI - Text Data Information) containing timing, text, and extension data. STL is the standard format for European broadcast workflows, DVD authoring, and DVB subtitling in EBU member countries.

Features

Generates a valid EBU STL GSI header block with standard metadata fields

Converts SRT timestamps (HH:MM:SS,mmm) to 25fps STL timecodes (HH:MM:SS:FF)

Maps subtitle text into properly formatted TDI data blocks

Sets default vertical position and justification codes

Handles UTF-8 to EBU character set mapping where possible

Outputs .stl files compatible with European broadcast systems

Why Convert?

STL is required for subtitle delivery to European broadcast television networks (BBC, ARD, France Televisions).

DVD authoring systems in Europe use STL as a standard subtitle import format.

EBU member broadcasters exchange subtitle files in STL format.

STL preserves 25fps frame-accurate timing for European PAL broadcast.

European DVB subtitling workflows use STL as the source format.

STL includes structured metadata (title, language, translator) that broadcast workflows require.

Convert subtitles produced for international use into the format European broadcasters expect.

Format Differences

SRT is a simple plain-text list; STL uses structured GSI header and TDI data blocks.

SRT uses HH:MM:SS,mmm timestamps; STL uses HH:MM:SS:FF frame-based timecodes at 25fps.

SRT has no metadata section; STL includes a GSI header with program title, language, and translator.

SRT text is variable-length UTF-8; STL uses fixed-width text fields with EBU character encoding.

SRT has no positioning; STL includes vertical position and justification codes per entry.

SRT is universal; STL is specific to European broadcast and DVD workflows.

Common Use Cases

European Broadcast Delivery

Produce STL files from SRT subtitles for delivery to European broadcasters like BBC, ARD, or France Televisions that require EBU format.

DVD Authoring

Import subtitles into European DVD authoring systems that accept STL as a standard subtitle format.

DVB Subtitling

Prepare subtitle content for DVB (Digital Video Broadcasting) workflows that use STL as the source format.

Broadcast Metadata

Include program title, language, and translator metadata in the STL GSI header for broadcast workflow integration.

Multi-Format Distribution

Produce both SRT (for streaming) and STL (for broadcast) from the same subtitle source for multi-platform delivery.

Subtitle Localization

Convert internationally-produced subtitles to STL for European localization and broadcast distribution.

Related Formats

SRT (SubRip)

The input format: universal plain-text subtitles readable by all media players and editors.

SCC (Scenarist Closed Captioning)

The North American broadcast equivalent: convert SRT to SCC for US broadcast delivery.

TTML (Timed Text Markup Language)

The XML-based alternative: some modern broadcast workflows use TTML/EBU-TT instead of STL.

Frequently Asked Questions

What is the EBU STL format used for?

EBU STL (Tech 3264) is the European Broadcasting Union standard for subtitle file exchange between broadcast systems. It encodes subtitles in a binary format with a GSI (Global Screen Information) header and TTI (Text Timing Information) blocks. BBC, ARD, France Televisions, RAI, and other European broadcasters use STL for television subtitle delivery.

What frame rate should I use for STL conversion?

STL supports multiple frame rates (23.976, 24, 25, 29.97, 30 fps). European broadcasters typically use 25 fps (PAL), while film-originated content may use 24 fps. The converter defaults to 25 fps for European broadcast compatibility but allows you to specify the correct frame rate.

Does STL support character sets beyond ASCII?

STL supports multiple character code tables defined in the GSI header (CCT field). The converter handles UTF-8 input and maps characters to the appropriate STL code table, supporting accented characters common in European languages.

How does the GSI header work in STL files?

The GSI (Global Screen Information) header is a 1024-byte binary block at the start of every STL file containing metadata like the programme title, episode number, language code, creation date, and revision number. The converter generates a valid GSI header automatically from your SRT file.

How are SRT timestamps converted to STL timecodes?

SRT timestamps in HH:MM:SS,mmm format are converted to STL EBU timecodes in HH:MM:SS:FF format, where FF is the frame number (0-24 for 25fps). Millisecond values are mapped to the nearest frame number based on the selected frame rate.

Is this SRT to STL converter free?

Yes, completely free with no sign-up, no watermarks, and no file size limits. All processing happens in your browser, so your subtitle files are never uploaded to a server.

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Related Resources

What is SRT?What is STL?