Net::sip is a perl framework that provides many useful tools with which to write software for sip endpoints (e.g phones, answer machines), sip proxies and registrars. it contains no gui and no real code for working with video or audio, though it does have some support for rtp (no rtcp) and working with pcmu/8000 data, enough for sending pcmu/8000 encoded audio to a sip peer and for receiving and saving pcmu/8000 audio data.