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SMPTE Timed Text in the UltraViolet™ Common File Format. Mike Dolan (TBT). SMPTE Timed Text in the UltraViolet™ Common File Format. Requirements & History Relationship to SMPTE Timed Text Extensions Profiles & Constraints Further Reading. Requirements. Subtitles
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SMPTE Timed Text in the UltraViolet™ Common File Format Mike Dolan (TBT)
SMPTE Timed Text in the UltraViolet™ Common File Format • Requirements & History • Relationship to SMPTE Timed Text • Extensions • Profiles & Constraints • Further Reading
Requirements • Subtitles • (language translation of dialog) • Comparable to DVD & Blu-ray functionality • Closed Captions • (transcription of sound) • Comparable to CEA-708 as constrained by FCC 47CFR79.102
Development History • Subtitle design started in early 2009 • DVB Subpictures first considered • W3C TTML (known as DFXP then) proposed in late 2009 • SMPTE-TT (with TTML) decided in early 2010 • W3C TTML published in late 2010 • SMPTE-TT published in late 2010 • Refinements and constraints developed since
Relationship to TTML & SMPTE-TT SMPTE-TT CFF-TT W3C TTML
The Base “TT” Namespaces (1/3) • W3C TTML • Designed to be general purpose for many use cases, not just subtitles and captions • A rich design destined to be subsetted for applications • SMPTE-TT Extensions • Images • Metadata
The Base “TT” Namespaces (2/3) • SMPTE-TT Extensions – Images • Definition inline in the document or by external URI • PNG format • Inline encoding via “Base64” • Attributes to insert in a region and define justification
The Base “TT” Namespaces (3/3) • SMPTE-TT Extensions – Metadata • General metadata defined for television caption conversion: • Source format (e.g. “CEA-608”) • Conversion attributes • General data carriage • Inline encoding via “Base64” • Used for “tunneling” data (e.g. exact original CEA-608 data byte pairs)
CFF-TT Extension • cff:forcedDisplayMode • Support for “forced” subtitles • Even when subtitle track is not enabled, some special case text/images are displayed
Example XML … <div> <p region="subtitle1" begin="00:05:00" end="00:05:15“ cff:forcedDisplayMode=”true”> This subtitle text is always displayed even when the subtitle track is not selected. </p> </div> …
Profiles • Text • 708 FCC subset functionality • Well-defined Unicode for most Western languages • No image support • Image • SMPTE-TT PNG file support • Mainly intended for font glyphs • No text support
Constraints - General • Some TTML infrastructure complexity not needed to meet requirements • Root container = video track width and height • Only 4 Active Regions maximum within root container • Simplified attribute syntax and semantics • e.g. media timebase, text metrics • Detailed Rendering Model • Maximum document size • Character and Image buffer model • Character and Image rendering throughput
Constraints – Text Profile • (all image-related attributes and elements forbidden) • Anamorphic text forbidden • Blurred text forbidden
Constraints – Image Profile • (all text-related attributes and elements forbidden)
Further Reading • DECE CFF Specification • http://www.uvvu.com/uv-for-business.php • SMPTE-TT PDA • https://www.smpte.org/PDA_On-demand/SMPTE-TT • SMPTE-TT Standards Overview • https://www.smpte.org/sites/default/files/st2052-0-2010.pdf • W3C TTML 1.0 2nd Edition (draft) • http://dvcs.w3.org/hg/ttml/raw-file/tip/ttml10/spec/ttaf1-dfxp.html
The End • Author - Michael Dolan, TBT • DECE Technical Working Group Co-Chair • Member of SMPTE 24TB and W3C TTWG • mailto:mdolan@newtbt.com • Questions?