One Way Audio/ No Audio Problems

by **Admin** Wed Jan 02, 2019 2:41 am

One-way Audio/No Audio is a common VoIP problem. It is one of the most frequent support questions we receive. There are many possible causes.

Outdated firmware in routers, VoIP phones, Firewalls, etc. can cause one-way audio. Ensure you have the latest updates for all the devices in the call path.
Firewall mistakenly blocking RTP, be sure firewalls configured correctly
Particularly if NAT is involved in the call path, configuration of the various devices may be a problem. Please click here for NAT configuration on Telcobridges devices
Another reason for one way audio is having your system set to offering unsupported codecs within your other SIP systems.
- Please check the following link for TB supported codecs; Voice Codecs
- Check if the codecs are configured correctly in the SDP; Profile SDP Description
Just as each side of a call must send RTP within the same codec, each side must also have the same phase timing (or ptime value). Profile SDP Description
Configured RTP port ranges can cause a problem too. Check FreeSBC and endpoints (Clients, SIP Trunks) are using correct RTP ports. RTP Port Range
High one-way packet loss. If sufficient packet loss occurs in one direction on a call, that half of the conversion may break down, but not cause the entire call to drop. Packet loss can occur due to a number of reasons:
- High utilization on a link with no QoS.
- Misconfigured interface: Half-duplex or duplex mismatch.
- Underperforming network devices.
- Cabling faults.
Wrong threshold configuration under SBC Advanced parameter can cause FreeSBC to block RTP-Audio by the firewall due to thresholds. You can see the following error in your call trace;
** Data path error;
-Blocking all packets due to excessive packets/bandwidth from network
Please double check your thresholds configuration from;
Code:
SBC -> Advanced parameters

Please check the following wiki for more troubleshooting steps; FreeSBC Troubleshooting Guide