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

Profile Atom GuidelinesUniversal FeaturesNote A writer that records the QuickTime Audio Codec type for the 'mp4a' codec is encouragedalso to write the MPEG-4 Audio Codec feature.Feature Value AlgorithmThe feature value is the audio codec type read from a SoundDescription structure’s dataFormat field. Ifthere are multiple sample descriptions with different audio codec types, either all QuickTime Audio CodecType features must be recorded in the profile atom or none must be recorded.Reader ResponsibilitiesA reader of this feature code should compare the recorded value by an equality comparison (using =) with theformat codes supported by the reader.MPEG-4 Video ProfileContaining profile atomTrack (video), moviepart-ID0x20202020 (universal feature)feature-code'm4vp'feature-valueUnsigned int(32) where least significant 8 bits hold the profile_and_level_indication from thevisual_object_sequence, as defined in specification ISO/IEC 14496-2, retrieved from the videoparameters for the MPEG-4 video codec description. The top 24 bits must be set to 0.Feature ValuesThe least significant 8 bits hold the value. The most significant 24 bits of the feature value should be set to 0.Writer ResponsibilitiesA writer of the MPEG-4 video profile feature should record the 8 bits corresponding to theprofile_and_level_indication from the visual_object_sequence, as defined in specification ISO/IEC14496-2, found in the video parameters encoded in the esds of the MPEG-4 video codec sample description(with QuickTime codec type 'mp4v').2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.406