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

Media Data Atom TypesVideo MediaColor table IDA 16-bit integer that identifies which color table to use. If this field is set to –1, the default color tableshould be used for the specified depth. For all depths below 16 bits per pixel, this indicates a standardMacintosh color table for the specified depth. Depths of 16, 24, and 32 have no color table.If the color table ID is set to 0, a color table is contained within the sample description itself. The colortable immediately follows the color table ID field in the sample description. See “Color Table Atoms” (page46) for a complete description of a color table.Video Sample Description ExtensionsVideo sample descriptions can be extended by appending other atoms. These atoms are placed after the colortable, if one is present. These extensions to the sample description may contain display hints for thedecompressor or may simply carry additional information associated with the images. Table 4-2 (page 158) liststhe currently defined extensions to video sample descriptions.Table 4-2Extensiontype'gama''fiel''mjqt''mjht''esds'Video sample description extensionsDescriptionA 32-bit fixed-point number indicating the gamma level at which the image wascaptured. The decompressor can use this value to gamma-correct at display time.Two 8-bit integers that define field handling. This information is used by applicationsto modify decompressed image data or by decompressor components to determinefield display order. This extension is mandatory for all uncompressed Y´CbCr dataformats. The first byte specifies the field count, and may be set to 1 or 2. A value of 1is used for progressive-scan images; a value of 2 indicates interlaced images. When thefield count is 2, the second byte specifies the field ordering: which field contains thetopmost scan-line, which field should be displayed earliest, and which is stored first ineach sample. Each sample consists of two distinct compressed images, each codingone field: the field with the topmost scan-line, T, and the other field, B. The followingdefines the permitted variants: 0 – There is only one field. 1 – T is displayed earliest, Tis stored first in the file. 6 – B is displayed earliest, B is stored first in the file. 9 – B isdisplayed earliest, T is stored first in the file. 14 – T is displayed earliest, B is stored firstin the file.The default quantization table for a Motion-JPEG data stream.The default Huffman table for a Motion-JPEG data stream.An MPEG-4 elementary stream descriptor atom. This extension is required for MPEG-4video. For details, see “MPEG-4 Elementary Stream Descriptor Atom ('esds')” (page 160).2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.158