src: libn: stream: sink: Enable Nack

[joaoantoniocardoso]

Supposedly this is all we need to make the retransmission work with the RFC4588.

I checked the resulting SDP, and it has all it needs:

Sender (this branch):

v=0
o=- 2461340508447355243 0 IN IP4 0.0.0.0
s=-
t=0 0
a=ice-options:trickle
a=group:BUNDLE video0
m=video 9 UDP/TLS/RTP/SAVPF 96 97
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:Imt2ypYqN8nzjQx6HzC6smEMvF+OvhaA
a=ice-pwd:MYE+ApE38JDaDQgwKN7B3LvJ53RA4BcH
a=rtcp-mux
a=rtcp-rsize
a=sendonly
a=rtpmap:96 H264/90000
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 transport-cc
a=framerate:30
a=rtpmap:97 rtx/90000
a=ssrc-group:FID 3729522813 1429131839
a=ssrc:3729522813 msid:user3977049223@host-7363340d webrtctransceiver0
a=ssrc:3729522813 cname:user3977049223@host-7363340d
a=ssrc:1429131839 msid:user3977049223@host-7363340d webrtctransceiver0
a=ssrc:1429131839 cname:user3977049223@host-7363340d
a=mid:video0
a=fingerprint:sha-256 45:AA:A2:F0:17:F9:16:70:03:37:BE:F9:8A:6F:8A:14:60:CB:F2:F4:B6:40:BA:46:E4:3F:45:08:5B:C0:1B:C6
a=rtcp-mux-only
a=fmtp:97 apt=96

Receiver (chrome):

o=- 5019588695368733316 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE video0
a=msid-semantic: WMS
m=video 9 UDP/TLS/RTP/SAVPF 96 97 (20 more lines) mid=video0
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:xlmo
a=ice-pwd:7Hhi/bfvtrZH9EIJ3U4YqFXd
a=ice-options:trickle
a=fingerprint:sha-256 9A:9A:C0:F3:B3:66:16:C6:79:68:FD:AF:F5:D2:45:26:F3:04:EA:1E:B4:64:B8:6F:6C:5E:70:42:90:83:FD:89
a=setup:active
a=mid:video0
a=recvonly
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 H264/90000
a=rtcp-fb:96 transport-cc
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=fmtp:96 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42e01f
a=rtpmap:97 rtx/90000
a=fmtp:97 apt=96

[rafaellehmkuhl]

Sick!