SIP Inbound Trunk - One-Way Audio Issue

Telephony
1

Hello Team,

I’m reaching out regarding a critical issue with our voice agent implementation using LiveKit Cloud and SIP inbound trunks. We’re experiencing one-way audio problems where the agent can hear callers perfectly, but callers cannot hear the agent’s responses.

Any guidance would be greatly appreciated.

2

Thank you for the quick response!

I downloaded and analyzed the PCAP from the dashboard. Here’s what I found:

RTP Analysis:
The PCAP shows ONE RTP stream:

  • Source: 10.42.8.95 (LiveKit) → Dest: 185.XX.XXX.XX (Caller)
  • Codec: G.711 µ-law (PCMU)
  • Packets: 1,038 packets sent
  • Lost: 0% packet loss
  • Duration: ~20 seconds
  • Quality: Good (low jitter)

So LiveKit IS sending RTP packets to the caller, but the caller hears complete silence.

From my side (caller):

  • I can hear nothing from the agent
  • But the agent hears me perfectly (STT worked and transcribed my speech correctly)
  • The agent generated a response (I saw it in the logs)
  • Just no audio coming through

The RTP data is traveling from LiveKit to me (1,038 packets), but there’s no audible sound. Could this be an issue with the audio payload in the RTP packets?

Let me know if you need any other information!

3

I see you also contacted support. I responded to the email. But basically, in the PCAP, I see RTP packets from LiveKit.

I did not understand why your to and from address are both xxx.sip.livekit.cloud. Are you doing that on purpose? If so, what is your use case for why you would do that?