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

Media Data Atom TypesSubtitle MediaTable 4-12Subtitlesampleextension'frcd'Subtitle sample extensionsDescriptionThe presence of this atom indicates that the sample contains a forced subtitle. Thisextension has no data.Forced subtitles are shown automatically when appropriate without any interactionfrom the user. If any sample contains a forced subtitle, the Some Samples Are Forced(0x40000000) flag must also be set in the display flags.Consider an example where the primary language of the content is English, but theuser has chosen to listen to a French dub of the audio. If a scene in the video displayssomething in English that is important to the plot or the content (such as a newspaperheadline), a forced subtitle displays the content translated into French. In this case, thesubtitle is linked (“forced”) to the French language sound track.If this atom is not present, the subtitle is typically simply a translation of the audiocontent, which a user can choose to display or hide.'styl''tbox''twrp'Style information for the subtitle. This atom allows you to override the default style inthe sample description or to define more than one style within a sample. See “SubtitleStyle Atom” (page 203).Override of the default text box for this sample. Used only if the 0x20000000 displayflag is set in the sample description and, in that case, only the top is considered. Evenso, all fields should be set as though they are considered. See “Text Box atom” (page204).Text wrap. Set the one-byte payload to 0x00 for no wrapping or 0x01 for automaticsoft wrapping.Subtitle Style AtomThis extension specifies changes to the appearance of a subtitle. The style information in the subtitle sampledescription provides the default style for the subtitle text. This extension allows you to override the defaultstyle for different parts, or all, of the subtitle text.SizeAn unsigned 32-bit integer holding the size of the subtitle style atom.TypeAn unsigned 32-bit field containing the four-character code 'styl'.Entry countAn unsigned 16-bit integer specifying how many subtitle text style records follow this entry count.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.203