Fix OPUS/48000/1 for RTSP from some cameras

Again, trying to make WebRTC work with OPUS audio from Thingino.

streams:
  terreiro:
  - rtsp://thingino:thingino@192.168.1.39/ch1

Maybe it's because it's OPUS/1 not OPUS/2? Maybe it's the same reason why #1505 is happening.

{
  "producers": [
    {
      "id": 14,
      "format_name": "rtsp",
      "protocol": "rtsp+tcp",
      "remote_addr": "192.168.1.39:554",
      "url": "rtsp://thingino:thingino@192.168.1.39/ch1",
      "sdp": "v=0\r\no=- 1733960107351613 1 IN IP4 192.168.1.39\r\ns=thingino prudynt\r\ni=stream1\r\nt=0 0\r\na=tool:LIVE555 Streaming Media v2024.11.28\r\na=type:broadcast\r\na=control:*\r\na=range:npt=now-\r\na=x-qt-text-nam:thingino prudynt\r\na=x-qt-text-inf:stream1\r\nm=video 0 RTP/AVP 96\r\nc=IN IP4 0.0.0.0\r\nb=AS:5000\r\na=rtpmap:96 H264/90000\r\na=fmtp:96 packetization-mode=1;profile-level-id=64001E;sprop-parameter-sets=Z2QAHqw7UFAX/LCAAAADAIAAABlC,aO48gA==\r\na=control:track1\r\nm=audio 0 RTP/AVP 97\r\nc=IN IP4 0.0.0.0\r\nb=AS:32\r\na=rtpmap:97 OPUS/48000\r\na=control:track2\r\n",
      "user_agent": "go2rtc/1.9.7",
      "medias": [
        "video, recvonly, H264",
        "audio, recvonly, OPUS/48000"
      ],
      "receivers": [
        {
          "id": 20,
          "codec": {
            "codec_name": "h264",
            "codec_type": "video",
            "level": 30,
            "profile": "High"
          },
          "childs": [
            87,
            169
          ],
          "bytes": 28946303,
          "packets": 24551
        },
        {
          "id": 62,
          "codec": {
            "codec_name": "opus",
            "codec_type": "audio",
            "sample_rate": 48000
          },
          "childs": [
            63,
            66
          ],
          "bytes": 5499651,
          "packets": 34589
        }
      ],
      "bytes_recv": 35188634
    }
  ],
  "consumers": [
    {
      "id": 56,
      "format_name": "rtsp",
      "protocol": "rtsp+tcp",
      "remote_addr": "127.0.0.1:36056",
      "sdp": "v=0\r\no=- 1 1 IN IP4 0.0.0.0\r\ns=go2rtc/1.9.7\r\nc=IN IP4 0.0.0.0\r\nt=0 0\r\nm=audio 0 RTP/AVP 96\r\na=rtpmap:96 OPUS/48000\r\na=control:trackID=0\r\n",
      "user_agent": "go2rtc/1.9.7",
      "medias": [
        "audio, sendonly, ALL"
      ],
      "senders": [
        {
          "id": 63,
          "codec": {
            "codec_name": "opus",
            "codec_type": "audio",
            "sample_rate": 48000
          },
          "parent": 62,
          "bytes": 5499651,
          "packets": 34589
        }
      ],
      "bytes_send": 6053075
    },
    {
      "id": 61,
      "format_name": "rtsp",
      "protocol": "rtsp+tcp",
      "remote_addr": "127.0.0.1:36084",
      "sdp": "v=0\r\no=- 1 1 IN IP4 0.0.0.0\r\ns=go2rtc/1.9.7\r\nc=IN IP4 0.0.0.0\r\nt=0 0\r\nm=audio 0 RTP/AVP 96\r\na=rtpmap:96 OPUS/48000\r\na=control:trackID=0\r\n",
      "user_agent": "FFmpeg Frigate/0.14.1-f4f3cfa",
      "medias": [
        "audio, sendonly, OPUS"
      ],
      "senders": [
        {
          "id": 66,
          "codec": {
            "codec_name": "opus",
            "codec_type": "audio",
            "sample_rate": 48000
          },
          "parent": 62,
          "bytes": 5499651,
          "packets": 34589
        }
      ],
      "bytes_send": 6053075
    },
    {
      "id": 86,
      "format_name": "rtsp",
      "protocol": "rtsp+tcp",
      "remote_addr": "127.0.0.1:45040",
      "sdp": "v=0\r\no=- 1 1 IN IP4 0.0.0.0\r\ns=go2rtc/1.9.7\r\nc=IN IP4 0.0.0.0\r\nt=0 0\r\nm=video 0 RTP/AVP 96\r\na=rtpmap:96 H264/90000\r\na=fmtp:96 packetization-mode=1;profile-level-id=64001E;sprop-parameter-sets=Z2QAHqw7UFAX/LCAAAADAIAAABlC,aO48gA==\r\na=control:trackID=0\r\n",
      "user_agent": "FFmpeg Frigate/0.14.1-f4f3cfa",
      "medias": [
        "video, sendonly, ANY"
      ],
      "senders": [
        {
          "id": 87,
          "codec": {
            "codec_name": "h264",
            "codec_type": "video",
            "level": 30,
            "profile": "High"
          },
          "parent": 20,
          "bytes": 28301630,
          "packets": 24015
        }
      ],
      "bytes_send": 28685870
    },
    {
      "id": 168,
      "format_name": "webrtc",
      "protocol": "ws+udp",
      "remote_addr": "192.168.1.15:49875 host",
      "user_agent": "Mozilla/5.0 (Windows NT 10.0; Win64; x64) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/131.0.0.0 Safari/537.36",
      "medias": [
        "video, sendonly, VP8, VP9, H264, AV1",
        "audio, sendonly, OPUS/48000/2, G722/8000, PCMU/8000, PCMA/8000, L16, PCML"
      ],
      "senders": [
        {
          "id": 169,
          "codec": {
            "codec_name": "h264",
            "codec_type": "video"
          },
          "parent": 20,
          "bytes": 5764018,
          "packets": 4851
        }
      ],
      "bytes_send": 5833856
    }
  ]
}

PS: MSE works.

I have never saw OPUS/48000 without /2. I don't think that's the standard at all. It needs to be further investigated.

As Thingino is open source, I can try to change it to output in OPUS/48000/2.

I really cannot comment whether this is a standard or not, but I guess it makes sense to send a single audio track given there is a single microphone. Two audio tracks would use more data, I suppose, for no good reason.

What is your opinion about it? Do you think I should try to patch Thingino?

I am also seeing this on a OpenIPC camera, https://opus-codec.org/ list mono and stereo as part of the specification.
Indicates to just duplicate the channel in this situation.

Of course OPUS can support mono any other bitrates. But I'm not sure about OPUS in the RTSP:

https://datatracker.ietf.org/doc/html/rfc7587

 Example 1: Standard mono session with 48000 Hz clock rate

       m=audio 54312 RTP/AVP 101
       a=rtpmap:101 opus/48000/2

You are right:
https://datatracker.ietf.org/doc/html/rfc7587#section-7

   o  The media subtype ("opus") goes in SDP "a=rtpmap" as the encoding
      name.  The RTP clock rate in "a=rtpmap" MUST be 48000, and the
      number of channels MUST be 2.

So Thingino and OpenIPC are currently non compliant.

Additionally, since opus/48000/2 is the only valid definition, maybe makes sense to regexp replace all opus to 48000/2 in the incoming SDP and avoid future issues with non compliant servers.

Additionally, since opus/48000/2 is the only valid definition, maybe makes sense to regexp replace all opus to 48000/2 in the incoming SDP and avoid future issues with non compliant servers.

Do you think that would be enough to make it work?

I've manually adjusted this in prudynt to opus/2 and it worked with go2rtc webrtc. Only in internal testing, not production. Uncertain if it will cause problems with other clients though.

Fix OPUS/48000/1 for RTSP from some cameras #1506

@AlexxIT

@AlexxIT integrated a fix: 0d6b8fc. Exciting! I will try it as soon as possible.

Yes, I got some cameras sent to me for testing that have the same codec. So it was easy to fix and test.

@AlexxIT

@AlexxIT, out of curiosity, was this camera you got running thingino too?

No. It was https://openipc.org/ firmware.

https://github.com/AlexxIT/go2rtc/releases/tag/v1.9.8

Fix OPUS/48000/1 for RTSP from some cameras AlexxIT#1506

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Fix OPUS/48000/1 for RTSP from some cameras #1506

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