VoIP and DTMF decoding

Discussion in 'VOIP' started by John M., Feb 24, 2004.

  1. John M.

    John M. Guest

    I plan to implement an IVR solution using VoIP.

    A VoIP gateway/router connects my telco voice circuits to the Ethernet
    (G.711) and my app server is simply a Linux box. The app answers call,
    plays an audio prompt, receives a touchtone DTMF reply, and then streams
    the selected pre-recorded audio program.

    QUESTION: Does VoIP have DTMF decoding built-in to the protocol?
    Or would my app server have to decode the raw PCM digital audio in
    order to detect the touch tones? Are there routines to do this already?

    Any advice appreciated. THANKS!
    John M., Feb 24, 2004
    #1
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  2. John M.

    Jack L. Guest

    John M. wrote:
    > QUESTION: Does VoIP have DTMF decoding built-in to the protocol?
    > Or would my app server have to decode the raw PCM digital audio in
    > order to detect the touch tones? Are there routines to do this
    > already?


    I think that softwares such as Gnophone and Linphone has a C-library which
    handles DTMF decoding. Maybe they can inspire you.

    --
    Mvh / Best regards,
    Jack, Copenhagen

    The email address is for real. :)
    Jack L., Feb 24, 2004
    #2
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  3. (John M.) wrote in
    news::

    > A VoIP gateway/router connects my telco voice circuits to the Ethernet
    > (G.711) and my app server is simply a Linux box. The app answers call,
    > plays an audio prompt, receives a touchtone DTMF reply, and then streams
    > the selected pre-recorded audio program.
    >
    > QUESTION: Does VoIP have DTMF decoding built-in to the protocol?


    Yes, I know for certain that H.323 has several ways to send DTMF signals to
    endpoints (be it inband, as RFC<mumble> data or as H.245 UserInformation
    signals). The problem is what is your gateway doing. If it uses inband
    DTMF, you're in some sort of trouble, because now the endpoint has to
    decode the DTMF from the media stream, otherwise it's easy.

    --
    Andreas
    Andreas Sikkema, Feb 24, 2004
    #3
  4. DTMF decoding (using SIP) can be inband, using RFC2833 or SIP-info (maybe
    more).
    My "Handytone ATA-286" adapter and BudgetPhone does this
    (http://www.telappliant.com).

    I have made a simple VoIP server program, that receives DTMF tones as
    RFC2833 or SIP-info, and answers back with inband (g711) sounds.
    Was easy to do, as the decoding was just to read data passing by and not by
    decoding sound patterns.

    --
    Christen Fihl
    http://HSPascal.fihl.net
    Christen Fihl, Feb 24, 2004
    #4
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