What can I do about poor voice quality when using softphone?

Question:
What can I do about poor voice quality when using softphone?

Solution 1
Remove the following codecs from the list of available codecs in the SIP gateway on the XPhone Connect administration interface (Telephony > Gateways > SIP) or alternatively put them in the back of the list

- OPUS
- G722

Solution 2
Poor voice quality during conferences in connection with Softphone may occur due to a set bypass media flag. Remove this flag in the SIP gateway on the XPhone Connect administration interface (Telephony > Gateways > SIP).

Solution 3
Set the following registry keys on your client computer:
Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters.

Parameters: REG_DWORD
Name: DisableUserTOSSetting
Value: 0

Parameter: REG_SZ
Name: Do not use NLA
Value: 1

Also check the steps from the following article:

https://www.c4b.com/de/knowledgebase/xcc/analyse-sprachqualitaet.php

Solution 4 (applies from V9):

In some cases the registry keys mentioned below had to be set in V8. These can lead to the above mentioned problem in V9, accordingly we recommend to remove the following keys in V9 if you or your customer are affected by the issue.

Path:
[HKEYCURRENTUSER\Software\C4B\Softphone\ReadOnly]

Remove the following values:

"JitterBufferSize"="0"
"NAudioSinkBufferSize"="25"
"NAudioSourceBufferSize"="25"