rohc team mailing list archive

[Didier Barvaux <question219552@xxxxxxxxxxxxxxxxxxxxx>]

Question #219552 on rohc changed:
https://answers.launchpad.net/rohc/+question/219552

    Status: Open => Answered

Didier Barvaux proposed the following answer:
> I use iftop and my router as 2 different tools to mesure
> outgoing bandwith in 2 different cases.
>     - When the tunnel is up and my call goes through the tunnel.
>     - When the tunnel is down and my call goes directly to my voip
>        switch.
> In those 2 situations, I get the same results.

If you monitor your SIP/RTP streams with iftop, they'll appear as
uncompressed because iftop monitors the streams before they got
compressed. You can monitor the UDP/5000 stream generated by the tunnel
instead, however the IP/UDP encapsulation added by the tunnel will not
give you accurate numbers about the ROHC compression.


> How can I tell my library to use RTP profiles?

The ROHC library provides 2 ways to tell it that one UDP stream is one RTP stream:
 - a list of UDP ports configured with rohc_comp_add_rtp_port() [1]
 - a callback function called for every UDP packet and defined with rohc_comp_set_rtp_detection_cb() [2]

These functions are not available on the 1.5.x versions. They will be
shipped with the to-be-released 1.6.0 version. Use the main dev branch
in the meantime.

[1] http://bazaar.launchpad.net/~didier-barvaux/rohc/main/view/head:/src/comp/rohc_comp.c#L1368
[2] http://bazaar.launchpad.net/~didier-barvaux/rohc/main/view/head:/src/comp/rohc_comp.c#L1157


> Apart from the tunnel, what other way to compress rtp do I have?

The ROHC library is a library, so it is intended to be used in other
programs. The library itself does not provide a standalone program
(except the tunnel tool for testing purposes).

Regards,
Didier

-- 
You received this question notification because you are a member of ROHC
Team, which is an answer contact for rohc.