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

Media Data Atom TypesPacketization Hint Sample Data for Data Format 'rtp 'Packetization Hint Sample Data for Data Format 'rtp 'This section describes the sample data for the 'rtp ' format. The 'rtp ' format assumes that the server issending data using Real-Time Transport Protocol (RTP). This format also assumes that the server “knows” aboutRTP headers but does not require that the server know anything about specific media headers, including mediaheaders defined in various IETF drafts.Each sample in the hint track will generate one or more RTP packets. Each entry in the sample data table in ahint track sample corresponds to a single RTP packet. Samples in the hint track may or may not correspondexactly to samples in the media track. Data in the hint track sample is byte aligned, but not 32-bit aligned.The RTP timestamps of all packets in a hint sample are the same as the hint sample time. In other words, packetsthat do not have the same RTP timestamp cannot be placed in the same hint sample.The RTP hint track time scale should be reasonably chosen so that there is adequate spacing between samples(as well as adequate spacing between transmission times for packets within a sample).The packetization hint sample data contains the data elements listed in Table 4-20 (page 259).Table 4-20Packetization hint data elementsPacketization hint sample dataEntry countReservedPacket entry tableAdditional dataBytes22VariableVariableField descriptionsEntry countA 16-bit unsigned integer indicating the number of packet entries in the table. Each entry in the tablecorresponds to a packet. Multiple entries in a single sample indicate that the media sample had to besplit into multiple packets. A sample with an entry count of 0 is reserved and, if encountered, must beskipped.ReservedTwo bytes that must be set to 0.Packet entry tableA variable length table containing packet entries. Packet entries are defined below.2012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.259