VoiceMail Codec Renegotiation

Dear All,

I want to have an idea about the possibility of forcing the VoiceMail to renegotiate codecs based on this scenario:
Let’s suppose that I have 2 messages in my VoiceMail: M1 is registered under G711 & M2 is registered under G729. I want to hear M1 & the welcoming message with G711 & M2 with G729 without making transcoding.
Is it possible to force the VoiceMail to do that? develop a function allowing that? or modifying chan_sip?

Thank you for your help.

The version of the audio file with the lowest cost codec will be used, although one would normally have all the versions with the same contents.

On the other hand, I can’t work out what you are really trying to do.

Thank you David for your response.
I want that the user will hear the voicemails with the best possible quality.
The normal scenario is to hear all the messages with the same codec. Is it possible to force the Voicemail to change the codec & renegociate even by adding a module or modifying one of the files of Asterisk? In other words, can Voicemail send a re-invite?