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

Profile Atom GuidelinesUniversal FeaturesNote A writer that records the QuickTime Video Codec type for the 'mp4v' codec is encouragedalso to write the MPEG-4 Video Profile feature.Feature Value AlgorithmThe feature value is the video codec type read from a QuickTime ImageDescription’s cType field. If there aremultiple sample descriptions with different video codec types, multiple video codec type features should berecorded in the profile atom.Reader ResponsibilitiesA reader of this feature code should compare the recorded value by an equality comparison (using =) with theformat codes supported by the reader.QuickTime Audio Codec TypeContaining profile atomTrack (sound), moviepart-ID0x20202020 (universal feature)feature-code'afmt'feature-valueUnsigned int(32) (a four-character-code) holding the QuickTime audio codec type copied fromSoundDescription structure’s dataFormat fieldFeature ValuesThis is the four-character-code found in a sound sample description.Examples: 'mp4a', 'twos'.Writer ResponsibilitiesA writer of the QuickTime audio codec type feature should record the four-character-code corresponding tothe QuickTime audio format type or types also recorded in the sound track’s sample descriptions.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.405