I'm facing a wired situation in sip calling using Portsip sdk. While I'm using dtmf method INFO and stop processing both incoming and outgoing audio during sip calling I can hear the dtmf tones. But when I'm using dtmf method RFC2833 and stop processing both incoming and outgoing audio, I can't hear the dtmf tones. I want to know, if it is the default feature of INFO and RFC2833.
With SIP INFO, DTMF is sent out-of-band, as part of the SIP dialog, so you don't need to be processing the audio streams to receive it. With RFC2833, DTMF is sent in-band, in specially marked RTP packets, so if you are not receiving or processing the audio streams, you will not hear DTMF either.
As a simple example, using SIP INFO and the default port for SIP, you would be getting your DTMF on UDP port 5060. Using RFC2833, you would be getting it on whatever epheremal port was negotiated for the RTP stream, e.g. UDP 20542.
Here is a brief introduction to the different options for sending DTMF with SIP