HI all,
I have a question on SIP Media Loopback
The SDP format for a SIP Endpoint initiating a loop back call appears as below.
( As per the draft
http://tools.ietf.org/html/draft-ietf-mmusic-media-loopback-14)
m=audio 41352 RTP/AVP 0 8 100
a=loopback:rtp-media-loopback
a=loopback-source:0 8 100
a=rtpmap:0 pcmu/8000
a=rtpmap:8 pcma/8000
a=rtpmap:100 G7221/16000/1
As seen above, two lines ( m line and a=loopback-source) carry the RTP payload
types. When loopback-mode is specified as loopback-source, the media format
corresponds to the RTP payload types thesource is willing to send. When
loopback-mode is specified as loopback-mirror, the media format corresponds to
the
RTP payload types the mirror is willing to receive. The payload types specified
in m= line for a loopback-source specify the payloads the source is willing to
receive.
The question is what does it mean if the payload type numbers in m= line and
loopback-source line are different as below?
m=audio 41352 RTP/AVP 112 113
a=loopback:rtp-pkt-loopback
a=loopback-source:0 8
a=rtpmap:112 encaprtp/8000
a=rtpmap:113 rtploopback/8000
Can any SIP endpoint ever receive media on some payload types and send media on
a different payload type? The draft doesn't speak much about such a scenario.
Many Thanks,
Bharat
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