[SIPForum-discussion] Decoding G711 audio

mfc at aol.in mfc at aol.in
Thu May 22 08:47:32 UTC 2008

I thank you for your valuable information and time, Mr. Malcom. I've selected the SIP INFO message way of doing this. Thanks again and I really appreciate your help. There's just the third question left unanswered and I'm hoping that someone would answer that too. :-)

Rajesh R.


-----Original Message-----
From: Malcolm Howlett <malcolm at c3.co.uk>
To: discussion at sipforum.org
Sent: Thu, 22 May 2008 1:33 pm
Subject: Re: [SIPForum-discussion] Decoding G711 audio



From: mfc at aol.in
[mailto:mfc at aol.in] 

Sent: 22 May 2008 06:26

To: discussion at sipforum.org

Subject: [SIPForum-discussion]
Decoding G711 audio


 AHello all,

I have a few queries and I am totally new to VoIP.

|1. Is there a way to
convert G711 (both alaw and mulaw) back to PCM? I searched through the internet
and am still |searching,
but I thought I will put up this query to you people as someone might have
experienced this problem |already.

Well at a minimum there are lots of people
who do hardware cards with DSPs that do it. Aculab, Pika technologies are 2
companies that spring to mind, not a cheap alternative

2. How are DTMF tones transmitted over a SIP call? If I dial say 34 when a call
is mature, how is this tone sent to the other end? What are the commands used?
Is it sent as a MESSAGE?


Any one of (and indeed combination of) 3

In band audio – dependant on the
audio codec as some of them can’t carry it

RFC2833 – negotiated in SDP

SIP INFO messages

3. Is there a way to retrieve all the registered client information (the client
extension and ID/name) from the SIP Server/Registrar? Is this possible? Can you
provide me some leads to a program or some API/Functions?



I thank you all for your time. I appreciate it.

Warm Regards,

Rajesh R.

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