ANSI SCTE-27-2011 pdf download SUBTITLING METHODS FOR BROADCAST CABLE
2.2 Stream Type for Subtitling Messages
Stream type 0x82 shall be used for program subtitles defined in this Standard.
2.3 Section and Data Structure Syntax Notation
This document contains symbolic references to syntactic elements. These references are typographically distinguished by the use of a different font (e.g., restricted), may contain the underscore character (e.g., sequence_end_code) and may consist of character strings that are not English words (e.g., dynrng). The formats of sections and data structures in this document are described using a C-like notational method employed in ISO/IEC 13818-1. An extension to this method is described below. Each data structure is described in a table format wherein the size in bits of each variable within that section is listed in a column labeled “Bits.” The column adjacent to the bits column is labeled “Bytes” and indicates the size of the item in bytes. For convenience, several bits within a particular byte or multi-byte variable may be aggregated for the count. An example follows:
In the byte count column, items that are conditional (because they are within a loop or conditional statement) are parenthesized. Nested parentheses are used if the loops or conditions are nested.
3 REFERENCES
3.1 Normative References
1. ISO/IEC 13818-1:2007 Information Technology — Generic coding of moving pictures and associated audio – Part 1: Systems.
2. ISO: “ISO 639.2, Code for the Representation of Names of Languages — Part 2: alpha-3 code,”as maintained by the ISO 639/Joint Advisory Committee (ISO 639/JAC),http://www.loc.gov/standards/iso639-2/iso639jac.html.
3.2 Informative References
3. EBU Tech. 3264-E, Specification of the EBU Subtitling Data Exchange Format, European Broadcasting Union, February 1991.
4 OVERVIEW OF SUBTITLE SYSTEM DESIGN
This section provides an overview of systems concepts involved in this Standard.
4.1 Bitmapped Subtitles
The transmission format for subtitles consists of one or more compressed bitmap images, along with optional rectangular backdrops for each. With the bitmap method, any language can be supported, as opposed to those supported within the memory of the Decoder and, the author of the subtitle stream has complete control over the appearance of the characters: the font (size and serif or sans-serif, for example), and kerning. In addition, characters and symbols which are not a part of any standard ROM-based character set can be transmitted and displayed, such as those characters in ideographic languages which represent proper names.