I read a number of the replies to this, but couldn't find an obvious
place to jump in, so I'm just replying here.
An offer multiple audio and/or video m-lines does not mean that they are
*alternatives*. Absent some explicit indication, there is no way to know
what the offerer's intent is in offering them, nor does the offerer know
what the answerer's intent is in accepting them.
In the given example, if the offerer only intends to use one audio and
one video, then it can arbitrarily choose one, and hope that this works
reasonably for the answerer. In that case it should do another O/A and
reject the ones it doesn't intend to use.
If you are designing phone1, and your goal is to have one audio and one
video, but you want to offer more possibilities than you can express
with one audio and one video m-line, then post back with what you are
trying to accomplish, and we can discuss recommended ways of achieving that.
Thanks,
Paul
On 4/16/14 2:51 AM, isshed wrote:
Hi All,
I have 1 basic query regarding ofer-answer model
Phone1 is sending the offer with 2 audio mlines and 2 video mline like
as follows.
m=audio 3342 RTP/SAVP 0 8 127
a=crypto:7 AES_CM_128_HMAC_SHA1_80 inline:2222222222
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:127 telephone-event/8000
m=audio 3342 RTP/AVP 0 8 127
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:127 telephone-event/8000
m=video 5544 RTP/SAVP 109
a=crypto:8 AES_CM_128_HMAC_SHA1_80 inline:3333333333
a=rtpmap:109 H264/90000
a=fmtp:109 profile-level-id=42800d
m=video 5544 RTP/AVP 109
a=rtpmap:109 H264/90000
a=fmtp:109 profile-level-id=42800d
and phone 2 is responding with all the 4 m lines as follows
m=audio 4344 RTP/SAVP 0 8 127
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:127 telephone-event/8000
m=audio 4344 RTP/AVP 0 8 119
a=sendrecv
a=rtpmap:0 PCMU/8000
a=rtpmap:8 PCMA/8000
a=rtpmap:119 telephone-event/8000
a=fmtp:119 0-15
m=video 7878 RTP/SAVP 109
a=crypto:8 8 AES_CM_128_HMAC_SHA1_80 inline:4444444444
a=rtpmap:109 H264/90000
a=fmtp:109 profile-level-id=42800d
m=video 7878 RTP/AVP 109
a=sendrecv
a=rtpmap:109 H264/90000
a=fmtp:109 profile-level-id=42801e; max-mbps=49000; max-br=20010; sar=13
Which m line should phone1 select to send and receive audio and video.
let me know is query is not clear.
Thanks,
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