Inline. Regards, Gaurav
-----Original Message----- From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of jc.huang Sent: Thursday, December 21, 2006 10:53 AM To: [email protected] Subject: Re: [Sip-implementors] Difference between G.711 and T.30 in RTPPackets The following are abstracted from rfc2833: Tone name frequency on period off period ______________________________________________________ CNG 1100 0.5 3.0 V.25 CT 1300 0.5 2.0 CED 2100 3.3 -- ANS 2100 3.3 -- ANSam 2100*15 3.3 -- V.21 "0" bit, ch. 1 1180 0.00333 V.21 "1" bit, ch. 1 980 0.00333 V.21 "0" bit, ch. 2 1850 0.00333 V.21 "1" bit, ch. 2 1650 0.00333 ITU dial tone 425 -- -- U.S. dial tone 350+440 -- -- They inspire me that implementing T.30 is the same as inbound DTMF does in RTP packets. GK>> That is true. I think you meant in-band DTMF instead of inbound DTMF. >Hi, >My coworker asks me what is the difference between G.711 and T.30 in RTP packets, they all are enclosed in RTP packets with the same payload size. I remembered T.30 was based on HDLC, but not clear how to implement it in Internet. Do SIP devices supporting T.30 use HDLC binary datas as RTP payload? GK>> Yes the do. >I know that SIP devices could specify free and valid payload type value for T.30. GK>> I don't think you'll achieve anything by specifying a payload type for T.30 as it is merely a signaling mechanism not a media/ payload carrier. T.38 is one of the payload types that you negotiate for fax applications as defined under http://www.iana.org/assignments/rtp-parameters (Refer Section for Dynamic Payload Types) The other alternative is obviously to send in-band fax using G711. >Thanks, > Thanks! ------------------ jc.huang _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors _______________________________________________ Sip-implementors mailing list [email protected] https://lists.cs.columbia.edu/cucslists/listinfo/sip-implementors
