[SIPForum-discussion] Decoding G711 audio

Malcolm Howlett malcolm at c3.co.uk
Thu May 22 08:03:48 UTC 2008




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


Hello 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 ways

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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