[SR-Users] kamailio + rtpengine: damaged media (Red Hat Linux)

[Richard Fuchs]

On 06/09/14 10:52, Alexey Rybalko wrote:
> Hello to all!
> 
> I encountered strange issue with rtpengine: voice during a call is heard
> like random binary data. (Video freezes during a video call). _It goes
> fine during 2-3 seconds_ before the media flow becomes glitched. It's
> related to SRTP calls only (RTP-SRTP, SRTP-RTP, SRTP-SRTP). RTP calls
> through mediaproxy are ok.
> 
> Used platform: Red Hat Linux 6.4, rtpengine (3.3.0 ?, latest form
> GitHub), kamailio (4.2.0-dev6) + websocket module. I have successfully
> installed (manually) mediaproxy daemon, Kamailio module, iptables
> library and kernel module. Kernel module was loaded (lsmod lists it,
> there are file in /proc/mediaproxy/0) and iptables were configured as
> expected.

Hard to tell what the problem is without looking at the RTP traffic. The
log looks fine. The delay you mentioned could indicate that it might be
the kernel module that's misbehaving. Perhaps you can try the same thing
again, but without the iptables rules installed (and/or without the
kernel module loaded), and see if that makes a difference.

> Mediaproxy log looks fine except of a few suspicious messages "No
> support for kernel packet forwarding available". I'm not sure they are
> related to the mentioned problem but I would like to have working kernel
> support. Attached example is for SIP-to-websocket call.

Those are actually expected on the RTCP ports, as RTCP is not supported
by the kernel module. I suppose the log messages shouldn't actually be
there for those ports.

> That would be great if you make any suggestions/comments on this issue.
> Need to mention that I haven't saw such problems on Debian Linux.

That's curious, perhaps something went wrong when compiling the kernel
module then? I have to admit that I have zero experience with rtpengine
on Red Hat myself.

> Couple of other questions:
> - What does message "Call-ID to delete not found" means?

Your SIP proxy sends two "delete" messages to rtpengine for some reason.
The first one already tears down the whole call, so the second one
triggers an error. No harm done, but also unnecessary.

> - "x_tables" is mentioned as required in the documentation for rtpengine
> kernel module (xt_MEDIAPROXY). Seems to be for Debian only. Is it
> required for other distros?

The x_tables module is a prerequisite for all xt_* modules. If you don't
have x_tables as a module (doesn't show up in lsmod), then perhaps it's
compiled into the kernel. You wouldn't be able to use iptables at all
without x_tables present.

cheers