Format of an SDP file for audio
v=0 o=- 1443716955 1443716955 IN IP4 10.xx.xxx.236 s=st2110 0-1-0 t=0 0 m=audio 20000 RTP/AVP 97 c=IN IP4 239.x.x.x/64 a=source-filter: incl IN IP4 239.x.x.x 10.xx.xxx.236 a=rtpmap:97 L24/48000/2 a=mediaclk:direct=0 rate=48000 a=framecount:48 a=ptime:1 a=ts-refclk:ptp=IEEE1588-2008:04-5c-6c-ff-fe-0a-53-70:127
Following is information about the data in this example:
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o=
This line identifies the source IP for the stream -
m=audio
. This identifies the file as an audio description.20000
is the port of the stream. This line must occur before thea
lines. -
c=
identifies the destination IP address. This is a unicast or multicast address. -
a=source-filter
identifies a filter. This line is optional.In a file for an input to Elemental Live:
-
If the line is included, Elemental Live will listen only to the source IP (10.xx.xxx.236) for packets.
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If the line isn't included, Elemental Live will listen to any packets on the destination IP address (239.x.x.x).
In a file for an output: Elemental Live always includes this line in any SDP file that it creates.
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-
a=rtpmap provides information about the audio format:
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An example for PCM:
a=rtpmap:97 L24/48000/2
L24
is the number of bits per PCM audio sample.48000
is the sample rate.2
is the number of channels, in this example, a single stereo track. -
An example for a Dolby Digital codec:
a=rtpmap:96 AM824/48000/5 a=fmtp:96 channel-order=SMPTE2110.(AES3,AES3)
48000
is the sample rate.6
is the number of AM824 subframe pairs, and must be an even number.
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