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

Media Data Atom TypesSubtitle MediaSubtitle text style recordOne or more records that provide details about the subtitle’s style. One record consists of the followingfields.Start characterA 16-bit value that is the offset of the first character that is to use the style specified in this record.Zero (0) is the first character in the subtitle.End characterA 16-bit value that is the offset of the character that follows the last character to use this style.Font identifierA 16-bit value that must be set to the same font identifier as in the font table ('ftab' extension).Font faceAn 8-bit integer that indicates the font’s style. Set this field to 0 for normal text. You can enableother style options by using one or more of the bit masks listed in Text.Font sizeAn 8-bit value that specifies the font’s size. See “Subtitle Sample Description” (page 200) for moreinformation.Foreground colorA 32-bit RGBA color that specifies the text’s color. See “Subtitle Sample Description” (page 200)for more information.Text Box atomThis optional extension defines a text box for a subtitle sample, to be used as described in Table 4-12 (page203). If present, this overrides the default text box in the associated sample description. If the subtitle sampledescription’s Display flags do not include the Vertical Placement flag (0x20000000), the Text Box atom shouldnot be included in any sample of the subtitle track.SizeAn unsigned 32-bit integer holding the size of the subtitle style atom.TypeAn unsigned 32-bit field containing the four-character code 'tbox'.Text boxA 64-bit rectangle that specifies an area to receive text (each 16 bits indicate top, left, bottom, and right,respectively) within the subtitle track. This rectangle must fill the track width dimensions exactly. The topand bottom coordinates can vary because they are used to place and size the subtitle text vertically. The2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.204