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Beginner

SPA303 dtmf issues

Hi,

We are using SPA303 (fw 7.4.8) configured with 'DTMF Tx Method' set to 'AVT'.

DTMFs are not being recognized by some of our providers. We've tested both with 'Yes' and 'No' in 'Mark All AVT Packets' option and got the same results.

We can see in captures first DTMF RTP Event packet comes out with EventDuration=0. According to RFC4733 it should not be 0.

We've checked this behavior in SPA9X2 and it sends first RTP Event packet three times with Event Duration not equal to 0.

Is there any way to change this initial event duration in SPA303 config?

Attached you'll find a capture with a DTMF digit coming from a SPA303 in AVT mode. The first RTP event packet has EventDuration = 0.

Thanks.

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Frequent Contributor

This is because of the chipset used in the 50x/30x series.  It's not a software programming error.

Basically the other side should accept the 0 in the 1st packet and then see the continuing packets for that DTMF where the event duration is increasing and the end of event is false, indicating the contination of that DTMF tone.  Only when the packet indicates end whereby end of event is true does the DTMF tone ceases to be transmitted.