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

Media Data Atom TypesHint MediaMovie Hint Info AtomA movie may contain an 'hnti' movie user data atom, which may contain one or more child atoms. The childatom contents start with 4 bytes that specify the transport and 4 bytes that specify the type of data containedin the rest of the child atom. Currently, the only defined transport is 'rtp ' (note the space) and the onlycontent data type defined is 'sdp ' (note the space). Child atoms whose transport or type combinations youdon’t recognize should be skipped.The text in an atom of type 'rtp sdp ' should be inserted (in the proper place) into the SDP informationgenerated from this file (for example, by a streaming server) before any SDP information for specific tracks.Table 4-17 (page 254) describes the type and values of the 'hnti' atom.Table 4-17The 'hinf' atom type containing child atomsType'trpY´'totl''nump''npck''tpyl''tpaY´'maxr''dmed''dimm''drep''tmin'Value8 bytes4 bytes8 bytes4 bytes8 bytes4 bytes8 bytes8 bytes8 bytes8 bytes4 bytesDescriptionThe total number of bytes that will be sent, including 12-byte RTP headers,but not including any network headers.4-byte version of 'trpY´The total number of network packets that will be sent (if the applicationknows there is a 28-byte network header, it can multiply 28 by this numberand add it to the 'trpY´ value to get the true number of bytes sent.4-byte version of 'nump'The total number of bytes that will be sent, not including 12-byte RTP headers.4-byte version of 'tpyl'The maximum data rate. This atom contains two numbers: g, followed by m(both 32-bit values). g is the granularity, in milliseconds. m is the maximumdata rate given that granularity.For example, if g is 1 second, then m is the maximum data rate over any 1second. There may be multiple 'maxr' atoms, with different values for g.The maximum data rate calculation does not include any network headers(but does include 12-byte RTP headers).The number of bytes from the media track to be sent.The number of bytes of immediate data to be sent.The number of bytes of repeated data to be sent.The smallest relative transmission time, in milliseconds.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.254