[SIPForum-discussion] RFC 2833 RTP Event

Fri Jun 22 05:56:48 UTC 2007

Hi Amit,

Are you talking about receiving packets over the network?

Since it comes over UDP, you should be able to receive them over an UDP 
socket as packets. On node A you need to open an UDP socket and listen on 
a particular port. On node B you should send UDP RTP packets over the same 
node.

Ethereal traces will help you determine towards which port the RTP packets 
are destined. So if you are expecting RTP from an unknown source (for 
which you can't control the RTP destination port this way should help)

If you are using a signaling control protocol like SIP to setup the RTP, 
then the RTP port info will be exchanged in the SIP offer-anser while call 
setup (m line of SDP will have it)

Once you are able to receive the packets over UDP, use a standart RTP 
header typecast to extract payload info, etc.

thanks,
Dipanjan

amit <amit.v at pyronetworks.com> 
Sent by: discussion-bounces at sipforum.org
06/22/2007 11:23 AM

To
Pradeep J <pradeep.jan at gmail.com>
cc
discussion at sipforum.org
Subject
Re: [SIPForum-discussion] RFC 2833 RTP Event

Hi pradeep,

i m already have ethereal.
ethereal shows the rtp event packets
but i m not able to capture these packets via JMF Or any other program.

you have any solution regarding this.

Thank you in advance.

       Amit 

On Fri, 2007-06-22 at 01:18 -0400, Pradeep J wrote:
Hi,
You can capture the RTP packets by taking the ethereal trace ..
The ethereal tool can be downloaded from www.winshark.com

Cheers,
Pradeep

On 6/20/07, amit <amit.v at pyronetworks.com> wrote:
Hi Onur,

you are right easy to decode the digit from the incoming RTP  packets. But 
i am not able to capture these RTP packets.

How I can capture these Packets Help me

Thank you in advance.

       Amit 

On Wed, 2007-06-20 at 13:21 +0300, Onur Cinar wrote:

Hi Amit,

Actually if you take a look at the RFC 2833 you should be able to easily 
decode the digit from the incoming packets. The payload is 32 bits:

8 bits  for event
1 bit  E flag
1 bit  R flag
6 bits volume
16 bits duration (in ms)

The first 8 bits hold the digit that you are looking for. Take a look at 
section 3.10 for the values.

Although you are only interested in the digits, take E flag in to account 
as well in order to make sure that you won't count the same digit more 
than one time. 

Regards,

-onur

---
Visit Nuvoiz.com for our SoftPhone Solutions!
A. Onur Cinar - Istanbul Office Manager
www.nuvoiz.com

On 6/20/07, amit <amit.v at pyronetworks.com> wrote:

Hi All,

I would like to read the specific DTMF digit from the received RTP Event. 
At the moment I detect that there are DTMF tones (RemotePayloadChangeEvent 
-> Payload 101), but I have no idea to receive the "RFC 2833 RTP Event", 
that I see in my Ethereal Capture. If I have this Event I think I can 
extract the Event ID... 

I would be pleased to see some ideas or helpfull code fragments how to 
receive this RFC 2833 RTP Event.

Thank you in advance.
Amit 

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-- 
Cheers,
Pradeep

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