G.729 코덱에서 DTMF입력

Posted at 2012/05/30 20:11 // in Tips // by Daniel

아, 그래서 ARS 입력이 안된 거였구나

There are some challenges with G.729. While it works great for voice communication, it doesn't do very well for things like faxing, data, and transmitting touch tones. This is because G.729 is designed specifically to translate voice, not data.

So if G.729 doesn't support touch tones, how is it you can do touch tones on a VoIP line? We'll explain that next time.


On VoIP, you can signal touch tones one of two-ways: in-band or out-of-band. In-band signaling only works with G.711 and even so, it's generally not recommended. The preferred method is therefore out-of-band signaling for touch tones, and is the only method supported with codecs like G.729.

There are two standards for DTMF signaling out-of-band in VoIP: RFC 2833, which is the common method, and SIP INFO, which can also signal this information. In both cases, they transmit when a particular touch tone has been activated and when the touch tone has been deactivated.

The challenge with both methods is correctly indicating when a particular button has been pressed and, more importantly, when it has been released. Both RFC 2833 and SIP INFO take this into account, but use different methods. RFC 2833 is the most common method and seems to be a bit more reliable than SIP INFO, based on my experience.

그러니까 RFC2833 형식으로 선택해서 써보면 되겠구나


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