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

Glossaryimage sequence A series of visual representationsusually represented by video over time. Imagesequences may also be generated synthetically, suchas from an animation sequence.image track Any track in a QuickTime movie thatcontains visual images. The term particularly appliesto video tracks that contain VR data.input map A data structure that describes whereto find information about tracks that are targets ofa modifier track. See modifier track.interlacing A video mode that updates half thescan lines on one pass and goes through the secondhalf during the next pass.interleaving A technique in which sound and videodata are alternated in small pieces, so the data canbe read off disk as it is needed. Interleaving allowsfor movies of almost any length with little delay onstartup.ISO Acronym for the International StandardsOrganization. ISO establishes standards formultimedia data formatting and transmission, suchas JPEG and MPEG.Joint Photographic Experts Group (JPEG) Refersto an international standard for compressing stillimages. This standard supplies the algorithm forimage compression. The version of JPEG suppliedwith QuickTime complies with the baseline ISOstandard bitstream, version 9R9. This algorithm isbest suited for use with natural images.key frame A sample in a sequence of temporallycompressed samples that does not rely on othersamples in the sequence for any of its information.Key frames are placed into temporally compressedsequences at a frequency that is determined by thekey frame rate. Typically, the term key frame is usedwith respect to temporally compressed sequencesof image data. See also sync sample. See also keyframe rate.key frame rate The frequency with which keyframes are placed into temporally compressed datasequences. See also key frame.layer A mechanism for prioritizing the tracks in amovie or the overlapping of sprites. When it plays amovie, QuickTime displays the movie’s tracksaccording to their layer—tracks with lower layernumbers are displayed first; tracks with higher layernumbers are displayed over those tracks.leaf atom An atom that contains only data, and noother atoms.LPCM Linear pulse-code modulation (LPCM) is amethod of encoding audio information digitally. Theterm also refers collectively to formats using thismethod of encoding. The term pulse-codemodulation (PCM), though strictly more general, isoften used to describe data encoded as LPCM. LPCMis PCM with linear quantization. See also PCM.matrix See transformation matrix.matte A defined region of a movie display that canbe clipped and filled with another display.media A data structure that contains informationthat describes the data for a track in a movie. Notethat a media does not contain its data; rather, amedia contains a reference to its data, which maybe stored on disk, CD-ROM disc, or any other massstorage device. Also called a media structure .media handler A piece of software that isresponsible for mapping from the movie’s timecoordinate system to the media’s time coordinatesystem. The media handler also interprets the2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.439