WebRTC generate invalid rtpmap for H264

[Olivier Crête]

Hi,

On Fri, 2021-04-09 at 19:22 +0200, Peter Biro wrote:
> Hi all,
> 
> I found a pretty strange issue webrtcbin generates the following
> initial SDP offer with a negative clock rate:
> 
> v=0
> o=- 5716970113760455593 0 IN IP4 0.0.0.0
> s=-
> t=0 0
> a=ice-options:trickle
> a=msid-semantic:WMS webrtc_sink
> m=video 9 UDP/TLS/RTP/SAVPF 96
> c=IN IP4 0.0.0.0
> a=setup:actpass
> a=ice-ufrag:0ybqQZNeS9CznnGxJxW/BpKyapc+CXsL
> a=ice-pwd:ffvVDjwSJ7/+AAdh3MjUMMhz91xwZZGI
> a=sendrecv
> a=rtcp-mux
> a=rtcp-rsize
> a=rtpmap:96 H264/-1784864736
> a=rtcp-fb:96 nack pli
> a=mid:video0
> a=fingerprint:sha-256
> 9B:11:48:BE:41:FF:CA:FE:62:B1:98:07:7B:E6:80:2A:56:9A:56:DC:A2:60:81:
> 27:DE:EC:F5:76:C1:C4:39:51
> 
> Actually it is more like a random number it changes in every session
> setup. However as I see it should be set to 9000.
> 
> My pipleine is pretty simple:
> 
> nvarguscamerasrc sensor-id=0 sensor-mode=0 gainrange="1 16"
> ispdigitalgainrange="1 1"
>     ! video/x-raw(memory:NVMM), width=(int)1920, height=(int)1080,
> format=(string)NV12, framerate=(fraction)30/1
>     ! nvvidconv ! nvv4l2h264enc bitrate=8000000 control-rate=1
> insert-sps-pps=true ! rtph264pay mtu=1400 
>     ! webrtcbin name=webrtc_sink latency=0
> 
> And on the application side Im handling the singling. 
> 
> Do you have any idea how to fix this? What I am missing here?

This is definitely a bug in webrtcbin, it shouldn't be generating an
SDP with an invalid clock rate.

Can you run it with "gst-launch-1.0 -v" to see wahtr caps the
payloaders set on webrtcbin ?

Do you set any codec preferences on webrtcbin ?

Olivier

> 
> Thanks,
> Peter
> 
> 
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-- 
Olivier Crête
olivier.crete at collabora.com

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