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See also: "RTP audio video profile

One of the design considerations of RTP is to carry a range of multimedia formats and allow new formats without revising the RTP standard. The design of RTP is based on the architectural principle known as "application level framing (ALF). The information required by a specific application's needs is not included in the generic RTP header, but is instead provided through RTP profiles and payload formats.[7] For each class of application (e.g., audio, video), RTP defines a profile and one or more associated payload formats.[7] A complete specification of RTP for a particular application usage requires profile and payload format specifications.[12]:71

The profile defines the codecs used to encode the payload data and their mapping to payload format codes in the field Payload Type (PT) of the RTP header. Each profile is accompanied by several payload format specifications, each of which describes the transport of a particular encoded data.[2] The audio payload formats include "G.711, "G.723, "G.726, "G.729, "GSM, "QCELP, "MP3, and "DTMF, and the video payload formats include "H.261, "H.263,[15] "H.264, and "MPEG-4.[15][16]

Examples of RTP Profiles include:

Packet header[edit]

RTP packet header
Bit offset[a] 0–1 2 3 4–7 8 9–15 16–31
0 Version P X CC M PT Sequence number
32 Timestamp
64 SSRC identifier
96 CSRC identifiers
...
96+32×CC Profile-specific extension header ID Extension header length
128+32×CC Extension header
...

The RTP header has a minimum size of 12 bytes. After the header, optional header extensions may be present. This is followed by the RTP payload, the format of which is determined by the particular class of application.[19] The fields in the header are as follows:

RTP-based systems[edit]

A functional network-based system includes other protocols and standards in conjunction with RTP. Protocols such as SIP, "Jingle, RTSP, "H.225 and "H.245 are used for session initiation, control and termination. Other standards, such as H.264, MPEG and H.263, are used to encode the payload data as specified via RTP Profile.[23]

An RTP sender captures the multimedia data, then encodes, frames and transmits it as RTP packets with appropriate timestamps and increasing sequence numbers. Depending on the RTP profile in use, the sender may set the Payload Type field. The RTP receiver captures the RTP packets, detects missing packets, and may reorder packets. It decodes the frames according to the payload format and presents the stream to its user.[23]

Standards documents[edit]

See also[edit]

Notes[edit]

  1. ^ Bits are ordered most significant to least significant; bit offset 0 is the most significant bit of the first octet. Octets are transmitted in "network order. Bit transmission order is medium dependent.

References[edit]

  1. ^ a b Daniel Hardy (2002). Network. De Boeck Université. p. 298. 
  2. ^ a b c Perkins 2003, p. 55
  3. ^ a b Perkins 2003, p. 46
  4. ^ "RFC 4571
  5. ^ Farrel, Adrian (2004). The Internet and its protocols. Morgan Kaufmann. p. 363. "ISBN "978-1-55860-913-6. 
  6. ^ Ozaktas, Haldun M.; Levent Onural (2007). THREE-DIMENSIONAL TELEVISION. Springer. p. 356. "ISBN "978-3-540-72531-2. 
  7. ^ a b c Larry L. Peterson (2007). Computer Networks. Morgan Kaufmann. p. 430. "ISBN "1-55860-832-X. 
  8. ^ a b Perkins 2003, p. 56
  9. ^ Peterson 2007, p. 435
  10. ^ Zurawski, Richard (2004). "RTP, RTCP and RTSP protocols". The industrial information technology handbook. CRC Press. pp. 28–7. "ISBN "978-0-8493-1985-3. 
  11. ^ "RFC 4566: SDP: Session Description Protocol, M. Handley, V. Jacobson, C. Perkins, IETF (July 2006)
  12. ^ a b c d e f g h i "RFC 3550
  13. ^ Multiplexing RTP Data and Control Packets on a Single Port. IETF. April 2010. RFC 5761. https://tools.ietf.org/html/rfc5761. Retrieved November 21, 2015. 
  14. ^ Collins, Daniel (2002). "Transporting Voice by using IP". Carrier grade voice over IP. McGraw-Hill Professional. pp. 47. "ISBN "0-07-136326-2. 
  15. ^ a b Chou, Philip A.; Mihaela van der Schaar (2007). Multimedia over IP and wireless networks. Academic Press. pp. 514. "ISBN "0-12-088480-1. 
  16. ^ Perkins 2003, p. 60
  17. ^ Perkins 2003, p. 367
  18. ^ Breese, Finley (2010). Serial Communication over RTP/CDP. BoD - Books on Demand. pp. [1]. "ISBN "978-3-8391-8460-8. 
  19. ^ Peterson 2007, p. 430
  20. ^ a b c Peterson 2007, p. 431
  21. ^ Perkins 2003, p. 59
  22. ^ a b Peterson, p.432
  23. ^ a b Perkins 2003, pp. 11–13

External links[edit]

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