[asterisk-dev] DTMF detection in dsp.c intolerant?

Steve Underwood steveu at coppice.org
Wed Aug 22 09:58:09 CDT 2007

Tony Mountifield wrote:
> In article <46CC389F.4040707 at coppice.org>,
> Steve Underwood <steveu at coppice.org> wrote:
>> Those files decode OK with the DTMF decoder in spandsp. Since the one in 
>> * is based on that, the problem must be due to something subtle in the 
>> differences.
> Hi Steve, many thanks for your reply. Would you mind running the following
> file through the same decoder?
> http://www.softins.co.uk/dtmf-call-31378.wav
> In this one the audio is not so clean, but I would have thought a good
> decoder should still be able to extract the DTMF.
> The string sent was again *82779736*91856360** but this time Asterisk
> only detected *87936*918636*
> I'll have a look at the decoder in spandsp and try to compare it with
> the one in Asterisk.
> BTW, I'm using Asterisk 1.2.
spandsp finds what you say is really there. If you have spandsp, the 
DTMF receiver test program can be used to decode wave file of 8k 
sample/second audio, with a command line:
    ./dtmf_rx_tests -d <file name>


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