SDP video codec negotiation

Hi folks,

 

I have a question about video codec negotiation, for example, in INVITE SDP, the video codec offer is

 

 

m=video 51684 RTP/AVP 117 115 113 34
a=label:VIDEO
a=rtpmap:117 H264/90000
a=fmtp:117 profile-level-id=64001f;packetization-mode=1;max-mbps=216000
a=rtpmap:115 H264/90000
a=fmtp:115 profile-level-id=42001f;packetization-mode=1;max-mbps=216000
a=rtpmap:113 H263-1998/90000
a=fmtp:113 CIF4=1;CIF=1;QCIF=1;SQCIF=1;D=1;F=1;I=1;J=1;L=1;S=1;T=1
a=rtpmap:34 H263/90000
a=fmtp:34 CIF4=1;CIF=1;QCIF=1;SQCIF=1
a=rtcp-fb:* nack
a=rtcp-fb:* nack pli
a=rtcp-fb:* ccm fir
a=rtcp-fb:* ccm tmmbr
a=rtcp-rsize
a=crypto:1 AES_CM_128_HMAC_SHA1_80 inline:gsclYca7rGO4SyavP1F4TsXz0IY4SFsgFGFrPKMT|2^31