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

Media Data Atom TypesPacketization Hint Sample Data for Data Format 'rtp 'FieldXMPayloadtypeBit#389-15DescriptionA 1-bit number corresponding to the extension (X) bit in the RTP header. Thisbit should probably not be set, since a server that needs to send its own RTPextension would either not be able to, or would be forced to replace anyextensions from the hint track.A 1-bit number corresponding to the marker (M) bit in the RTP header.A 7-bit number corresponding to the payload type (PT) field of the RTP header.All undefined bits are reserved and must be set to zero. Note that the location of the defined bits are inthe same bit location as in the RTP header.RTP sequence numberA 16-bit integer specifying the RTP sequence number for this packet. The RTP server adds a random offsetto this sequence number before transmitting the packet. This field allows re-transmission of packets—forexample, the same packet can be assembled with the same sequence number and a different (later)packet transmission time. A text sample with a duration of 5 minutes can be retransmitted every 10seconds, so that clients that miss the original sample transmission (perhaps they started playing themovie in the middle) will be refreshed after a maximum of 10 seconds.FlagsA 16-bit field indicating certain attributes for this packet. Defined bits are shown in Figure 4-16 (page261).Figure 4-16Packet attribute flagsEntry countA 16-bit unsigned integer specifying the number of entries in the data table.Extra information TLVsThe extra information TLVs listed in Table 4-23 (page 261) are present if and only if the X bit is set in theflags field. This provides a way of extending the hint track format without changing the version, whileallowing backward compatibility.Table 4-23Extra information TLVsExtra information TLVsExtra information sizeBytes42012-08-14 | © 2004, 2012 Apple Inc. All Rights Reserved.261