A little weird SDP problem

Sat Aug 14 16:55:38 UTC 2021

Hi,

I'm running a GST 18.4 python app. This app communicates with a Chrome JS app on the same network.

The app is able to send and receive VP8, but I'm having a problem with H.264, in case the Python app (webrtcbin based) is the ANSWERER. The problem is not there if the Python app is the OFFERER.

First the positive case: This is my H.264 pipeline in the Python app. If the Python app OFFERS, the video appears in Chrome.

# H.264 TEST VIDEO
PIPELINE_TEST_H264 = '''
webrtcbin name=webrtcbin bundle-policy=max-bundle stun-server=stun://stun.l.google.com:19302
videotestsrc is-live=true pattern=smpte ! video/x-raw,width=1280,height=720 ! videoconvert ! x264enc ! rtph264pay ! 
queue ! application/x-rtp,media=video,encoding-name=H264 ! webrtcbin.
'''

The SDP handshake is like so:

The OFFER sent:

2021-08-14 16:44:48,800 webrtc_client.py-INFO    : having sdp offer:
v=0
o=- 143230668495837560 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
c=IN IP4 0.0.0.0
a=setup:actpass
a=ice-ufrag:8OgtMvs3Zdn04lGPl61MEeQGtuq2XNS+
a=ice-pwd:GbtIZHC7CWPkgzNrnH7mWEtWNpaeWL5n
a=rtcp-mux
a=rtcp-rsize
a=sendonly
a=rtpmap:96 H264/90000
a=rtcp-fb:96 nack pli
a=framerate:30
a=fmtp:96 packetization-mode=1;profile-level-id=42c01f;sprop-parameter-sets=Z0LAH9kAUAW7AWoCAgKAAAADAIAAAB5HjBkk,aMuMsg==
a=ssrc:2817782937 msid:user2521903457 at host-548ae76e webrtctransceiver0
a=ssrc:2817782937 cname:user2521903457 at host-548ae76e
a=mid:video0
a=fingerprint:sha-256 1B:99:58:8C:F3:33:28:60:02:E6:11:66:74:B7:84:B4:D9:06:32:12:13:23:F0:E9:23:68:9D:C3:CC:79:85:C5

The ANSWER received (video flows):

2021-08-14 16:44:48,940 webrtc_client.py-INFO    : received sdp answer:
v=0
o=- 6562431427409268738 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
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:OoGw
a=ice-pwd:egHkzRQOlN6ADWLnaltQ6AkA
a=ice-options:trickle
a=fingerprint:sha-256 20:C2:D3:AA:37:07:31:87:FA:71:D4:20:CF:50:ED:07:EA:C8:B8:1D:EA:02:73:9C:7C:AC:24:5C:F3:C9:DA:60
a=setup:active
a=mid:video0
a=recvonly
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 H264/90000
a=rtcp-fb:96 nack pli
a=fmtp:96 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f

The video does not appear in Chrome, if Chrome is the OFFERER. The ANSWER confirms that with "a=inactive".

The OFFER generated by Chrome:

2021-08-14 16:47:03,340 webrtc_client.py-INFO    : received sdp offer:
v=0
o=- 6799643414674800834 2 IN IP4 127.0.0.1
s=-
t=0 0
a=group:BUNDLE 0
a=extmap-allow-mixed
a=msid-semantic: WMS
m=video 9 UDP/TLS/RTP/SAVPF 96 97 98 99 100 101 122 102 121 127 120 125 107 108 109 35 36 124 119 123 118 114 115 116 37
c=IN IP4 0.0.0.0
a=rtcp:9 IN IP4 0.0.0.0
a=ice-ufrag:Tyef
a=ice-pwd:tct8Z2AfUb1yNAT/aWDfj2OI
a=ice-options:trickle
a=fingerprint:sha-256 F6:01:90:DF:E5:67:4E:B0:9F:DF:14:1A:3B:08:2F:E8:12:ED:CC:35:EB:4D:E2:22:AF:1F:18:7C:EB:37:D7:41
a=setup:actpass
a=mid:0
a=extmap:1 urn:ietf:params:rtp-hdrext:toffset
a=extmap:2 http://www.webrtc.org/experiments/rtp-hdrext/abs-send-time
a=extmap:3 urn:3gpp:video-orientation
a=extmap:4 http://www.ietf.org/id/draft-holmer-rmcat-transport-wide-cc-extensions-01
a=extmap:5 http://www.webrtc.org/experiments/rtp-hdrext/playout-delay
a=extmap:6 http://www.webrtc.org/experiments/rtp-hdrext/video-content-type
a=extmap:7 http://www.webrtc.org/experiments/rtp-hdrext/video-timing
a=extmap:8 http://www.webrtc.org/experiments/rtp-hdrext/color-space
a=extmap:9 urn:ietf:params:rtp-hdrext:sdes:mid
a=extmap:10 urn:ietf:params:rtp-hdrext:sdes:rtp-stream-id
a=extmap:11 urn:ietf:params:rtp-hdrext:sdes:repaired-rtp-stream-id
a=recvonly
a=rtcp-mux
a=rtcp-rsize
a=rtpmap:96 VP8/90000
a=rtcp-fb:96 goog-remb
a=rtcp-fb:96 transport-cc
a=rtcp-fb:96 ccm fir
a=rtcp-fb:96 nack
a=rtcp-fb:96 nack pli
a=rtpmap:97 rtx/90000
a=fmtp:97 apt=96
a=rtpmap:98 VP9/90000
a=rtcp-fb:98 goog-remb
a=rtcp-fb:98 transport-cc
a=rtcp-fb:98 ccm fir
a=rtcp-fb:98 nack
a=rtcp-fb:98 nack pli
a=fmtp:98 profile-id=0
a=rtpmap:99 rtx/90000
a=fmtp:99 apt=98
a=rtpmap:100 VP9/90000
a=rtcp-fb:100 goog-remb
a=rtcp-fb:100 transport-cc
a=rtcp-fb:100 ccm fir
a=rtcp-fb:100 nack
a=rtcp-fb:100 nack pli
a=fmtp:100 profile-id=2
a=rtpmap:101 rtx/90000
a=fmtp:101 apt=100
a=rtpmap:122 VP9/90000
a=rtcp-fb:122 goog-remb
a=rtcp-fb:122 transport-cc
a=rtcp-fb:122 ccm fir
a=rtcp-fb:122 nack
a=rtcp-fb:122 nack pli
a=fmtp:122 profile-id=1
a=rtpmap:102 H264/90000
a=rtcp-fb:102 goog-remb
a=rtcp-fb:102 transport-cc
a=rtcp-fb:102 ccm fir
a=rtcp-fb:102 nack
a=rtcp-fb:102 nack pli
a=fmtp:102 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42001f
a=rtpmap:121 rtx/90000
a=fmtp:121 apt=102
a=rtpmap:127 H264/90000
a=rtcp-fb:127 goog-remb
a=rtcp-fb:127 transport-cc
a=rtcp-fb:127 ccm fir
a=rtcp-fb:127 nack
a=rtcp-fb:127 nack pli
a=fmtp:127 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42001f
a=rtpmap:120 rtx/90000
a=fmtp:120 apt=127
a=rtpmap:125 H264/90000
a=rtcp-fb:125 goog-remb
a=rtcp-fb:125 transport-cc
a=rtcp-fb:125 ccm fir
a=rtcp-fb:125 nack
a=rtcp-fb:125 nack pli
a=fmtp:125 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=42e01f
a=rtpmap:107 rtx/90000
a=fmtp:107 apt=125
a=rtpmap:108 H264/90000
a=rtcp-fb:108 goog-remb
a=rtcp-fb:108 transport-cc
a=rtcp-fb:108 ccm fir
a=rtcp-fb:108 nack
a=rtcp-fb:108 nack pli
a=fmtp:108 level-asymmetry-allowed=1;packetization-mode=0;profile-level-id=42e01f
a=rtpmap:109 rtx/90000
a=fmtp:109 apt=108
a=rtpmap:35 AV1X/90000
a=rtcp-fb:35 goog-remb
a=rtcp-fb:35 transport-cc
a=rtcp-fb:35 ccm fir
a=rtcp-fb:35 nack
a=rtcp-fb:35 nack pli
a=rtpmap:36 rtx/90000
a=fmtp:36 apt=35
a=rtpmap:124 H264/90000
a=rtcp-fb:124 goog-remb
a=rtcp-fb:124 transport-cc
a=rtcp-fb:124 ccm fir
a=rtcp-fb:124 nack
a=rtcp-fb:124 nack pli
a=fmtp:124 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=4d0032
a=rtpmap:119 rtx/90000
a=fmtp:119 apt=124
a=rtpmap:123 H264/90000
a=rtcp-fb:123 goog-remb
a=rtcp-fb:123 transport-cc
a=rtcp-fb:123 ccm fir
a=rtcp-fb:123 nack
a=rtcp-fb:123 nack pli
a=fmtp:123 level-asymmetry-allowed=1;packetization-mode=1;profile-level-id=640032
a=rtpmap:118 rtx/90000
a=fmtp:118 apt=123
a=rtpmap:114 red/90000
a=rtpmap:115 rtx/90000
a=fmtp:115 apt=114
a=rtpmap:116 ulpfec/90000
a=rtpmap:37 flexfec-03/90000
a=rtcp-fb:37 goog-remb
a=rtcp-fb:37 transport-cc
a=fmtp:37 repair-window=10000000

The ANSWER generated by webrtcbin:

2021-08-14 16:47:07,336 webrtc_client.py-INFO    : having sdp answer:
v=0
o=- 6799643414674800834 2 IN IP4 0.0.0.0
s=-
t=0 0
a=group:BUNDLE 0
m=video 9 UDP/TLS/RTP/SAVPF 96
c=IN IP4 0.0.0.0
a=ice-ufrag:ej11/cl3FCkkhNmNliiql1R5MX5MFn/g
a=ice-pwd:SgutRYS/iWj9l8WvWvXGzrohbIiTLK+f
a=mid:0
a=rtcp-mux
a=setup:active
a=rtpmap:96 VP8/90000
a=rtcp-fb:96 nack pli
a=rtcp-fb:96 ccm fir
a=inactive
a=fingerprint:sha-256 BD:5C:65:0E:D3:75:67:8B:80:71:57:D5:08:14:70:1A:BB:4F:51:F8:54:53:80:17:8C:3E:44:DB:EA:E5:04:06

What could be the problem or what to do to narrow it down?

TIA

-------------- next part --------------
An HTML attachment was scrubbed...
URL: <https://lists.freedesktop.org/archives/gstreamer-devel/attachments/20210814/96a7c8fa/attachment.htm>