[SIPForum-discussion] Behavior w.r.t RFC 2198 when "a=fmtp" attribute is not present in SDP

[Jagan Mohan]

Hi,

  As per RFC 2198, "ftmp" attribute could be used to describe the payload
type for primary and redundant audio, as shown below.

  m=audio 12345 RTP/AVP 121 0 5
  a=rtpmap:121 red/8000/1
  a=fmtp:121 0/5

  Say, offer present in the INVITE request from UAC does not have the "fmtp"
attribute, as shown below:

  m=audio 12345 RTP/AVP 121 0 5
  a=rtpmap:121 red/8000/1

  Then, how would the UAS interpret what codecs to use when RED payload type
is negotiated?

Thanks,
Jagan
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