We have a strange case which is a bit difficult to explain but I will try to keep it simple. The problem arises when two clients talk with each other using CSDK 4.2 and during the conversation one client receives a cellular call. If client accepts cellular call by holding SIP call, other client waits in hold mode which is fine. But after cellular call ends and SIP call un-held we receive a “could not start media” error with a code number 401 which causes call to fail and end. This happens almost all the time. So we can say that this case is consistent. When we check SIP traces we don’t see anything unusual or suspicious. CSDK sends a “Bye” signal to end the call. But actually no one ends the call, it just fails by itself at the moment of un-hold action.

Complete debul level log is in the attachment

Thanks for your questions, the logs here is a good source of information, I will review them with the team and get back to you.

Hi sercanoztorun,

Here is what our design team recommends -

"From the logs we see that the iOS Audio Unit wasn’t successfully initialized:
InitializeAudioUnit: Failed to initialize Audio Unit. Error: 561017449. Line: 638

This error (561017449) is defined in AVAudioSession.h:
AVAudioSessionErrorInsufficientPriority = '!pri', /* 0x21707269, 561017449 */
and is described as "The app was not allowed to set the audio category because another app (Phone, etc.) is controlling it."

Please make sure your app sets the Audio Session Category to “AVAudioSessionCategoryPlayAndRecord” prior to un-hold the VoIP session.

In general, the application should be always using this Audio Session Category when starting a VoIP session."

Does this resolve your issue?

Yes, your comment and suggestions were quite helpful. For others who may encounter similar problems I want to describe my case and solution. I use mode and options when set and activate AVAudioSession. Once I have added "AVAudioSessionCategoryOptionDuckOthers" option to try something and forgot to remove. I just removed that option which fixed my problem. Thanks again for your help.

The call transfer fails with the following TSAPI reason code: CSTA_UNIVERSAL_FAILURE_CONF, CONFERENCE_MEMBER_LIMIT_EXCEEDED

The following TSAPI reason code is returned when the agent tries to unhold the customer call: CSTA_UNIVERSAL_FAILURE_CONF, RESOURCE_BUSY mygiftcardsite balance