Difference between revisions of "RTP"

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=== RTP ===
=== RTP Protocol===


RTP (Real-time Transport Protocol) has been designed for the transport of multimedia streams over IP networks. Implementation is based on the User Datagram Protocol (UDP).  As IP networks are asynchronous, packets may be lost or delivered in different order.  RTP provides no guarantee of the delivery, but sequencing of the data makes it possible to detect missing packets.


RTP (Real-time Transport Protocol) has been designed for the transport of multimedia streams over IP networks. It works on top of UDP.
===Payload Type===
It was developed by the Audio-Video Transport Working Group of the IETF [http://en.wikipedia.org/wiki/IETF] and first published in 1996 as RFC 1889, and superseded by RFC 3550 in 2003.
describes the transport of a particular media format. Some values of the audio payload formats are standard others need to be described in a service description protocol, SDP (Session DescriptionProtocol);
 
IP networks are asynchronous and may lose or reorder packets.
 
Some fields in RTP are defined to address these problems:
 
'''Payload Type''' tags the content of the packet. Some standardized values exist, but for other codecs, the type must be described in a service description protocol, SDP (Session DescriptionProtocol);
 
The following table shows the defined RTP payload types used in Barix firmware.
The following table shows the defined RTP payload types used in Barix firmware.
Note that Payload types 0, 8, 10, 11 and 14 are defined by the RTP standard while types 96 to 112 (dynamic payload types) are Barix specific.
Note that Payload types 0, 8, 10, 11 and 14 are defined by the RTP standard while types 96 to 112 (dynamic payload types) are Barix specific.
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'''Sequence Number''' is primarily used to identify and detect lost packets and secondly to reconstruct the order in which packets where sent, which may make loss detection easier;
===Sequence Number===
 
is primarily used to identify and detect lost packets and secondly to reconstruct the order in which packets where sent, which may make loss detection easier;
'''Time Stamp''' is the sampling instant for the first octet of media data in a packet. It can be used to help recover the clock frequency at the receiving side, if it is not given by other means.


RTP does not include a loss recovery mechanism in case of packet losses.
===Time Stamp===
is the sampling instant for the first octet of media data in a packet. It can be used to help recover the clock frequency at the receiving side, if it is not given by other means.


Check the Wikipedia for an introduction to the topic [http://en.wikipedia.org/wiki/Real-time_Transport_Protocol].
===References===
Check the Wikipedia for an introduction to the RTP protocol [http://en.wikipedia.org/wiki/Real-time_Transport_Protocol].

Revision as of 18:14, 26 March 2009

RTP Protocol

RTP (Real-time Transport Protocol) has been designed for the transport of multimedia streams over IP networks. Implementation is based on the User Datagram Protocol (UDP). As IP networks are asynchronous, packets may be lost or delivered in different order. RTP provides no guarantee of the delivery, but sequencing of the data makes it possible to detect missing packets.

Payload Type

describes the transport of a particular media format. Some values of the audio payload formats are standard others need to be described in a service description protocol, SDP (Session DescriptionProtocol); The following table shows the defined RTP payload types used in Barix firmware. Note that Payload types 0, 8, 10, 11 and 14 are defined by the RTP standard while types 96 to 112 (dynamic payload types) are Barix specific.


RTP payload type
Audio Format
0
 μ-Law, 8bit, mono, 8kHz
8
 A-Law, 8bit, mono, 8kHz
10
 PCM 16bit, MSB first, signed, 44.1kHz stereo, left channel first
11
 PCM 16bit, MSB first, signed, 44.1kHz mono
14
 MPEG audio
96
 PCM, 16bit, MSB first, signed, 8kHz mono
97
 μ-Law, 8bit, mono, 24kHz
98
 A-Law, 8bit, mono, 24kHz
99
 PCM, 16bit, MSB first, signed, 24kHz mono
100
 μ-Law, 8bit, mono, 32kHzreserved
101
 A-Law, 8bit, mono, 32kHzreserved
102
 PCM, 16bit, MSB first, signed, 32kHz monoreserved
103
 PCM 16bit, MSB first, signed, 48kHz stereo, left channel first
104
 PCM, 16bit, LSB first, signed, 8kHz mono
105
 PCM, 16bit, LSB first, signed, 24kHz mono
106
 PCM, 16bit, LSB first, signed, 32kHz monoreserved
107
 PCM 16bit, LSB first, signed, 44.1kHz stereo, left channel first
108
 PCM 16bit, LSB first, signed, 48kHz stereo, left channel first
109
 μ-Law, 8bit, mono, 12kHz
110
 A-Law, 8bit, mono, 12kHz
111
 PCM, 16bit, MSB first, signed, 12kHz mono
112
 PCM, 16bit, LSB first, signed, 12kHz mono
127
 Generic (see below)


Sequence Number

is primarily used to identify and detect lost packets and secondly to reconstruct the order in which packets where sent, which may make loss detection easier;

Time Stamp

is the sampling instant for the first octet of media data in a packet. It can be used to help recover the clock frequency at the receiving side, if it is not given by other means.

References

Check the Wikipedia for an introduction to the RTP protocol [1].

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