Bad Voice Quality Happens when Calling from Linkus to Grandstream IP Phone


  • Firmware version: Any
  • Model: Linkus, Grandstream

Problem Description:

The calls from Linkus to Grandstream Phone exist a bad voice quality issue. The voice hears well if calls between Linkus. Also, calls from IP phone to IP phone are working.


Transcoding problem between iLBC to other codecs, all that seems the voice codes issue.

  • Capture the SIP packet on PBX, and reproduce the issue.
  1. make a call between Linkus and SIP phone.
  2. make a call between SIP phones.

Download the packet, it shows the iLBC Frame Size is using 30ms, And the Linkus mode is 20ms




Access the Grandsteam SIP phone WEB, and change the iLBC Frame Size to 20ms. Or remove iLBC codec.



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