Hint Track Information Atom ('hnti') in Movie User Data Atom

Hint track information atoms ('hnti') are defined both for movie-level user data atoms and for track-level user data atoms. The 'hnti' atom in the movie's user data atom contains hint information for the movie as a whole. This atom is not part of the hint track atom structure. It is contained in the user data atom ('udta') belonging to the movie atom that contains the hint track.

The 'hnti' atom contains child atoms that hold the actual hint information. Currently, only child atoms of type 'rtp ', subtype 'sdp ' are defined for 'hnti' atoms at the movie level. Servers should ignore child atoms whose type they do not recognize.

An RTP/SDP child atom has a 32-bit size field, a four-character type ('rtp '), a four-character subtype ('sdp '), and a data field. Note that the fourth character of the type 'rtp ' and the of the subtype 'sdp ' are both ASCII blanks (hex 20). Note also that this is different from the child atom of type 'sdp ' found in the track level user data atom.

The data field of an RTP/SDP atom contains a string with text used to build an SDP file, such as "a=x-qt-text-inf:Killer Streaming Movie". The string itself has no count byte or delimiter. It's length is calculated by subracting 8 from the atom size. A single string can contain multiple lines of SDP text, separated by a carriage-return and linefeed (0D 0A hex).

The SDP text must be inserted in the proper place in the SDP file in order to build an SDP file for this movie. SDP text taken from the movie-level 'hnti' atoms is inserted prior to SDP text taken from track-level 'hnti' atoms. Refer to the RFC for Session Description Protocol for precise line-ordering rules.

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