Vippie PC and Siplink are softphones for Windows  operating system (all versions). In the new release an implementation of  g729 codec has been added. Now the softphones support following voice codecs: g729, g723.1, g711a/u, GSM.    G.729 is an audio data compression algorithm for voice that compresses digital voice in packets of 10 milliseconds duration. Music or DTMF tones can only be transported reliably with this codec using the RTP Payload for DTMF Digits, Telephony Tones, and Telephony Signals as specified in RFC 2833. Because of its low bandwidth requirements, G.729 is mostly used in  VoIP applications where bandwidth must be conserved. Standard G.729 operates at a bit rate of 8 kbit/s.