Quicktime File Format (2012-08-14).pdf

Media Data Atom TypesSubtitle MediaSizeAn unsigned 32-bit integer holding the size of the font table atom.TypeAn unsigned 32-bit field containing the four-character code 'ftab'.CountAn unsigned 16-bit integer specifying how many fonts are described in this table. This must be 1.Font identifierAn unsigned 16-bit integer that identifies the font. This can be any number to uniquely identify this fontin this table, but it must match the font number specified in the subtitle sample description and in anyper-sample style records ('styl').Font name lengthAn unsigned 8-bit integer specifying the length of the font name in bytes.Font nameMust be either “Serif” or “Sans-Serif”.Subtitle Sample DataSubtitle sample data consists of a 16-bit word that specifies the length (number of bytes) of the subtitle text,followed by the subtitle text and then by optional sample extensions. The subtitle text is Unicode text, encodedeither as UTF-8 text or UTF-16 text beginning with a UTF-16 BYTE ORDER MARK ('\uFEFF') in big or little endianorder. There is no null termination for the text.Following the subtitle text, there may be one or more atoms containing additional information for selectingand drawing the subtitle.Table 4-12 (page 203) lists the currently defined subtitle sample extensions.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.202