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

Profile Atom GuidelinesUniversal FeaturesReader ResponsibilitiesA reader of the average audio bit rate feature value should compare the recorded value with its own limits todetermine if the content can be played. The reader should not perform an equality comparison (=) but insteada relative comparison (=).CommentsThe value of this feature should be deducible from information found in the sample table. Track edits normallyneed not be considered in the calculation for constant bit rate audio, but must be considered for variable bitrate audio or when track or movie segments containing constant bit rate audio are edited to alter their duration.QuickTime Video Codec TypeContaining profile atomTrack (video), moviepart-ID0x20202020 (universal feature)feature-code'vfmt'feature-valueUnsigned int(32) (a four-character-code) holding the QuickTime video codec type copied from theImageDescription structure’s cType fieldFeature ValuesThis is the four-character-code found in a video sample description.Examples: 'mp4v', 'jpeg'.Writer ResponsibilitiesA writer of the QuickTime video codec type feature should record the four-character code corresponding tothe QuickTime video format type or types also recorded in the video track’s sample descriptions.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.404