SPS/PPS missing on Describe

[cedricve]

Hey @mpromonet amazing work here!

I'm using the joy4 library and noticed that the Describe method using your RTSP server is missing codec information (which is unexpected and is deviating from the RFC). Is there any particular reason for this?

https://github.com/kerberos-io/joy4/blob/master/format/rtsp/client.go#L664

We receive something like this:

v=0
o=- 1656233372976675 1 IN IP4 192.168.1.234
s=LIVE555 Streaming Media v2022.06.16
i=LIVE555 Streaming Media v2022.06.16
t=0 0
a=tool:LIVE555 Streaming Media v2022.06.16
a=type:broadcast
a=control:*
a=range:npt=now-
a=x-qt-text-nam:LIVE555 Streaming Media v2022.06.16
a=x-qt-text-inf:LIVE555 Streaming Media v2022.06.16
m=video 0 RTP/AVP 26
c=IN IP4 0.0.0.0
b=AS:500
a=fmtp:26 
a=x-dimensions:1280,960
a=control:track1

But would expect to have an a=rtmap record for the codec like this.

< v=0
o=- 16601003535168796699 16601003535168796699 IN IP4 kerberos
s=Unnamed
i=N/A
c=IN IP4 0.0.0.0
t=0 0
a=tool:vlc 3.0.16
a=recvonly
a=type:broadcast
a=charset:UTF-8
a=control:rtsp://192.168.1.234:8554/stream1
m=video 0 RTP/AVP 96
b=RR:0
a=rtpmap:96 H264/90000
a=fmtp:96 packetization-mode=1;profile-level-id=640028;sprop-parameter-sets=J2QAKKwrQFAe0IAAAAMAgAAAHnJQABMSwAAvrze9wDxImoA=,KO4fLA==;
a=control:rtsp://192.168.1.234:8554/stream1/trackID=0

[mpromonet]

Hi @cedricve,

This is because your are capturing JPEG, the payload type 26. Your device should be able to capture H264 frame, then you will get an H264 stream with SPS & PPS.

Best Regards, Michel.

[cedricve]

Oh my god that explains it :) It’s indeed a USB camera, I was assuming to have your library doing internal encoding. My bad looks like it requires a passthrough with FFMPEG.

[mpromonet]

Hi,

The approach is lightweight, just capture frames from v4l2 interface and publish through RTSP, encoding can be done between the real device and a v4l2loopback one.

Best Regards, Michel.