[asterisk-dev] DTMF Volume

John Todd jtodd at digium.com
Mon Jul 7 11:50:57 CDT 2008

At 2:23 PM +0100 2008/7/3, Tony Redstone wrote:
>On Wed, Jul 2, 2008 at 7:00 PM, Konstantin Bokarius
><bokarius at comcast.net> wrote:
>>  When I tried to change that value to a negative, low (1-10), or very high
>>  number I did not notice any change with the DTMF volume.
>>  Are there other values that need to be changed - or am I missing something?
>The function you are looking it is for inserting real DTMF tones into
>the audio stream.  However, you've already said you're using rfc2833
>so you want to be looking at the ast_rtp_senddigit_*() functions in
>main/rtp.c instead.
>In each of the three senddigit functions, the value is set within the
>rtpheader[3]=... line.
>     rtpheader[3] = htonl((rtp->send_digit << 24) | (0xa << 16) |
>The volume is the 0xa value.  You need to increase this value to
>reduce DTMF volume.  I'm sure it goes without saying but read rfc2833
>to find out more regarding what the volume values correspond to.
>Hope this helps

It may be that volume control for DTMF would be useful from within 
the dialplan, possibly as a patch to the SendDTMF application with an 
additional modifier, perhaps with 0-10 as the scale.  This could then 
generically modify the volume either on an in-band transmission of 
DTMF or by translating to the requisite volume equivalent on RFC2833 

Patches welcome.


John Todd
jtodd at digium.com        +1-256-428-6083
Asterisk Open Source Community Director

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