What can I do against poor voice quality / one directional Audio when using softphone?

Question:
What can I do against poor voice quality / one directional Audio when using softphone?

Solution 1 (mostly helps against poor Audio quality)

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 (mostly helps against poor Audio quality and one directional Audio)

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 (mostly helps against poor Audio quality)

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 as of V9 mostly helps against one directional Audio)

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"

Solution 5 (applies as of V9 - helps with one-sided speech during a call):

If the voice transmission stops sporadically during a call, it can help to set the following parameter in the advanced settings of the SIP gateway:

Parameter:          GwB2BuaSetting_rtp-rewrite-timestamps
Value:                  true