Question #403402 on rohc changed:
https://answers.launchpad.net/rohc/+question/403402
Status: Answered => Open
gael anyouzoa is still having a problem:
I have taken notes about, i'm working into,i will reply about soon.
Le Dimanche 30 octobre 2016 12h08, Didier Barvaux
<[email protected]> a écrit :
Your question #403402 on rohc changed:
https://answers.launchpad.net/rohc/+question/403402
Status: Open => Answered
Didier Barvaux proposed the following answer:
Hello,
> I want to integrate rohc library on asterisk source code
> the aim is to modify the file "chan_sip.c (it's the sip channel for asterisk)
> i have already identified whick methods to modify
> but i'm not an expert on c language
> I need some orientation.
Integration of ROHC in Asterisk is a great idea! I think about it since
ages :)
Here is my understanding of ROHC integration in Asterisk:
1/ The chan_sip.c channel should be modified to support ROHC negotiation
through a custom SIP header "X-ROHC-Support" or the like.
2/ The ROHC compressor/decompressor shall be initialized when one RTP engine is
instanced in res/res_rtp_asterisk.c by chan_rtp.c ; they shall be destroyed
when the RTP stream is destroyed.
3/ The compression and decompression shall be performed in the RTP engine too
(rtp_sendto function probably). However the RTP header cannot be compressed
alone. The ROHC protocol and library work on IP/UDP/RTP headers altogether, not
on the RTP header alone. So, the UDP socket created by Asterisk in
create_new_socket() shall probably be modified into a RAW socket. The IP and
UDP headers shall therefore be built manually before compression. That's the
weird part :-/
> Yet, if there's others alternatives to make VoIP with ROHC,
> tell me more
You may try the IP/ROHC tunnel: https://rohc-
lib.org/wiki/doku.php#ip_rohc_tunnel
Your changes on Asterisk will handle SIP/RTP streams. The IP/ROHC tunnel
is a more generic solution, it handles all streams. However integration
would be better with Asterisk. Especially for detection of RTP streams.
>From within Asterisk, RTP streams can be detected from the SIP
exchanges.
Regards,
Didier
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