Ethereal-dev: RE: [Ethereal-dev] Building mpeg-4 dissector, help.
Hi,
A possible solution could be:
To get the dynamic payload type from an SDP description in a SIP call there is a problem in that at first a list of avalable codecs and you don't know which will be selected in the end. But from what I have seen the line :
Media Description, name and address (m): audio 20004 RTP/AVP 4
only contains one entry in the SIP/ACK where as it contains all avalable payload types in the 200 OK message :
Media Description, name and address (m): audio 14196 RTP/AVP 96 111 112 6 0 8 4 5 3 101
So then it should be possible to only store the "Conversations info" if only one codec is in the list, the next step would be to include the information
from :
Media Attribute (a): rtpmap:96 MP4V-ES/90000
( payload_type = 96, payload_type_str= MP4V-ES )
in the call to "conversations", conversation would forward the data in pinfo->private_data to the RTP dissector, the RTP dissector should do a lookup
on sub dissector based on payload_type_str and sub dissector should register the string in a new lookup table simmilar to "media type".
Emile could you post your dissector as it is at the moment ? I might be able to test it a bit.
Best regards
Anders
-----Original Message-----
From: ethereal-dev-bounces@xxxxxxxxxxxx
[mailto:ethereal-dev-bounces@xxxxxxxxxxxx]On Behalf Of Martin Regner
Sent: den 2 mars 2004 21:32
To: Ethereal development; Simon.Hailstone@xxxxxxxxxxxxxxxxxxx
Subject: Re: [Ethereal-dev] Building mpeg-4 dissector, help.
Martin Regner wrote:
> If there is no "conversation" started it could be started and some data
can
> be stored that will make RTP dissector to use a specific payload
dissector.
> If there is already a "conversation" some data can be set so that RTP
> disector will use a specific payload dissector for all packets for that
> "conversation".
>
The same "conversation" may be used for several different codecs (several
static and/or dynamic payload types),
so maybe we need to associate some data for a "conversation" that says that:
payload type 98 for this specific conversation and direction should be
disected with "rtpevent" dissector,
payload type 107 for this specific conversation and direction should be
dissected with "mpeg4" dissector.
(and maybe also have a possibility to specify that this is valid from
frame-number X to frame-number Y, but it may be better
to solve that in "conversation" mechnanism instead)
It could probably be possible for SDP dissector to store information about
payload-types and their corresponding codecs
when starting up a "conversation" when it sees the SDP message.
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