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

Profile Atom GuidelinesUniversal FeaturesCommentsBecause the QuickTime 'mp4a' codec may implement multiple audio decoders defined in specification ISO/IEC14496 in the future, this feature allows the reader to determine the specific audio decoder needed to interpretthe audio bit stream. The MPEG-4 Audio Codec feature should be present only if the 'mp4a' audio codec isused in a sound track.Maximum Video Size in a MovieContaining profile atomMoviepart-ID0x20202020 (universal feature)feature-code'mvsz'feature-valueA 32-bit packed structure holding width and height of the largest bounds needed to display the movieFeature ValuesA packed structure in a 32-bit value:struct {unsigned integer(16) width;unsigned integer(16) height;};In big-endian order, the top 16 bits correspond to the width. The lower 16 bits correspond to the height.Writer ResponsibilitiesA writer of the Maximum Movie Video Size feature should record a value that is equal to or greater than thedisplay size needed by the movie—the actual width and height needed to display the movie at its normal size,taking into account all matrices (all track matrices and the movie matrix).A writer (such as a CE device) may choose to record a constant size based upon its current recording modeeven if the actual size recorded in the movie is smaller.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.411