[Freeswitch-users] start_dtmf false positives

Roman Dissauer roman at dissauer.net
Tue Jan 30 14:05:12 UTC 2018


Hi,

In a quick check I recognized that spandsp_start_dtmf and start_dtmf use same function pointer dtmf_session_function. Seems I didn’t dig deep enough, just found out that spandsp_start_dtmf uses different algorithm.

Thanks for the hint Brian!
I’ll try out spandsp_start_dtmf and report back if issues are gone.

Kind Regards,
Roman


> Am 30.01.2018 um 13:08 schrieb Brian West <brian at freeswitch.com>:
> 
> spandsp_start_dtmf absolutely does NOT use libteletone, where exactly did you get that idea?
> 
> On Tue, Jan 30, 2018 at 4:51 AM, Roman Dissauer <roman at dissauer.net> wrote:
> Hi,
> 
> thanks Alexey, but spandsp_start_dtmf uses exactly same libteletone under the hood.
> 
> Kind Regards,
> Roman
> 
> RDI SOLUTIONS e.U.
> Rosasgasse 13/24
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>> Am 30.01.2018 um 00:06 schrieb Alexey Sibyakin <alex at freeswitch.com>:
>> 
>> Have you tried spandsp_start_dtmf? It has its quirks but after some tuning It worked for me much better than start_dtmf.
>> 
>> On Tue, Jan 30, 2018 at 1:15 AM, Steve Underwood <coppice12 at gmail.com> wrote:
>> The false positive rate for the DTMF decoder in spandsp is extremely low. Tests show it has one of the lowest false positive rates in the industry. If you are seeing significant false positives you might actually have some DTMF in the audio. Can you capture some troublesome audio to a file for analysis?
>> 
>> Regards,
>> 
>> Steve
>> On 01/29/2018 02:35 PM, Roman Dissauer wrote:
>>> Hi Guys,
>>> 
>>> we have troubles reliably recognizing DTMF tones by using dialplan application start_dtmf.
>>> From our carriers we get some calls with inband DTMF and some with RFC2833. To our customers we need to always do RFC2833. Therefore we check SDP information and enable start_dtmf when RFC2833 is not available on the incoming call. When start_dtmf is executed we have a lot of false positives mostly at the start of audio but also during the call.
>>> 
>>> Is there a way to prevent false DTMF detection? Does anyone have same issues and a solution for it?
>>> 
>>> Kind regards
>>> Roman Dissauer
>>> 
>>> RDI SOLUTIONS e.U.
>>> Rosasgasse 13/24
>>> 1120 Wien, Österreich
>>> T: +43 1 3530349 - 10
>>> F: +43 1 3530349 - 99
>>> roman.dissauer at rdi.at
>>> www.rdi.at
>>> 
>>> 
>>> 
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> 
> 
> _________________________________________________________________________
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> 
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> Brian West | Co-founder and Developer
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