![]() DTMF options įreeSWITCH attempts to negotiate rfc2833 DTMF out-of-band transmission.Īn option to offer rfc2833 but accept INFO was added in GIT bc7cb400c0d576817b12836012899925dce61cca on June 23, 2011. This AFAIK is the only DTMF intercept mode supported by FreeSWITCH ATM. ![]() Regenerate the detected DTMF tones on the opposite leg. ![]() 2.5 DTMF intercept w/ DTMF detection, removal and regeneration ĭetect DTMF using Goertzel and drop samples identified as containing DTMF tones. The opposite leg will hear silence (with or without some bleeding). 2.4 DTMF intercept w/ DTMF detection and removal ĭetect DTMF using Goertzel and drop samples containing DTMF tones. In some implementations this could be a cheaper operation than detect and remove. 2.3 DTMF intercept w/ DTMF removal ĭTMF is filtered out. DTMF detection is done by running Goertzel on each 20ms buffer but NOT dropping frames in which DTMF is detected. 2.2 DTMF passthrough inband w/ DTMF detection Īudio passes between the A and B legs without being modified. Mode descriptions 2.1 DTMF passthrough inband Īudio passes between the A and B legs without being inspected or modified. Two such triples would be needed to fully describe the behavior of two bridged channels: one for the rx and one for tx audio path. In the context of two bridged analog channels, we need to consider 5 possible approaches to DTMF handling per audio path (tx and rx).ĭTMF behavior for a single audio path can be captured by a triple of booleans as follows: The tones A, B, C, and D are very rare nowadays but they are still possible to send (e.g., someone has an old device with the extra ABCD column) and thus make sure that you handle them in your app, otherwise they may cause it to crash. When writing an application, make sure to handle all valid DTMF tones (with sound clips copied from the DTMF wikipedia page): 2.5 DTMF intercept w/ DTMF detection, removal and regeneration.2.4 DTMF intercept w/ DTMF detection and removal.2.2 DTMF passthrough inband w/ DTMF detection.
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