Проблема в пересылке dtmf тона при rfc2833

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Столкнулась с проблемой неправильной пересылки длины тона при тоновом наборе. Нет разницы по какому каналу идет звонок SIP или же IAX2. Это особенно ощутимо, когда звонят на конференцию, требующую ввести код доступа. Вот что видно в логах при неудачной попытке ввода:

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF begin '8' received on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF begin passthrough '8' on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end '8' received on SIP/1288-00000159, duration 60 ms

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end accepted with begin '8' on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end '8' detected to have actual duration 69 on the wire, emulation will be triggered on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end '8' has duration 69 but want minimum 80, emulating on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end emulation of '8' queued on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF begin '6' received on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF begin passthrough '6' on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end '6' received on SIP/1288-00000159, duration 60 ms

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end accepted with begin '6' on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end '6' detected to have actual duration 69 on the wire, emulation will be triggered on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end '6' has duration 69 but want minimum 80, emulating on SIP/1288-00000159

[Sep 1 16:59:34] DTMF[11823] channel.c: DTMF end emulation of '6' queued on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF begin '4' received on SIP/128800000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF begin passthrough '4' on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end '4' received on SIP/1288-00000159, duration 80 ms

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end accepted with begin '4' on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end '4' detected to have actual duration 69 on the wire, emulation will be triggered on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end '4' has duration 69 but want minimum 80, emulating on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end emulation of '4' queued on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF begin '4' received on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF begin passthrough '4' on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end '4' received on SIP/1288-00000159, duration 60 ms

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end accepted with begin '4' on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end '4' detected to have actual duration 69 on the wire, emulation will be triggered on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end '4' has duration 69 but want minimum 80, emulating on SIP/1288-00000159

[Sep 1 16:59:35] DTMF[11823] channel.c: DTMF end emulation of '4' queued on SIP/1288-00000159

[Sep 1 16:59:36] DTMF[11823] channel.c: DTMF begin '#' received on SIP/1288-00000159

[Sep 1 16:59:36] DTMF[11823] channel.c: DTMF begin passthrough '#' on SIP/1288-00000159

[Sep 1 16:59:36] DTMF[11823] channel.c: DTMF end '#' received on SIP/1288-00000159, duration 100 ms

[Sep 1 16:59:36] DTMF[11823] channel.c: DTMF end accepted with begin '#' on SIP/1288-00000159

[Sep 1 16:59:36] DTMF[11823] channel.c: DTMF end passthrough '#' on SIP/1288-00000159

Происходит это не постоянно, но с завидной частотой. Бывает зависит от скорости ввода кода доступа. Если подолгу держать каждую нажатую цифру, а в промежутках между нажатиями делать паузы - код принимается. Звонки совершаются с телефонов cisco spa504g и cisco 7905

Установлен Астериск 1.8.3 RFC2833 метод испульзуется из-за требований установленных "SKYPE CONNECT" и "SKYPE FOR ASTERISK". Буду благодарна любому дельному совету. Спасибо.