What Is IMSC-Rosetta?
IMSC-Rosetta is a standardized subtitle file format built atop IMSC (a TTML-based profile), designed for simplicity, clarity, and broad compatibility.
It maintains rich styling (colors, outlines, positioning), while simplifying TTML's typical complexity—making it ideal for parsing, creation, and modification without deep TTML knowledge.
Key Advantages
- Consistent, high-quality subtitles: Ideal for multilingual and multi-channel delivery.
- Streamlined structure: Reduces the complexity of XML/TTML and boosts implementability.
- Full feature support: Preserves styles like color, layout, boxing, and directionality for Japanese vertical subtitles.
- Interoperability: Supports reversible conversion to proprietary formats used in broadcasting with minimal feature loss.
- Flexible usage: Fits authoring, delivery, storage, archival, and translation workflows.
- Industry-backed: Developed with contributions from Yella Umbrella, WBD, BBC Studios, Ooona, Deluxe, and others.
Format & Tooling Support
IMSC-Rosetta files are XML-based TTML files (extensions .imscr or .xml) and supported by tools like Stellar Suite, Ooona and EZTitles for import/export, including advanced features such as ruby text, vertical Japanese, horizontal groups, and SDH styling.
The majority of subtitle vendors can reliably create IMSC-Rosetta files.
Get Involved
The full specification, sample files, and contributor resources are hosted on GitHub. The project invites feedback, issue reports, and contributions.