[Freeswitch-users] RTP delay with cng

[Jose Fco. Irles Durá]

Hi,

I have a FreeSWITCH 1.4.15 (from debian repositories), but I've been
having a problem for a long time (with older versions too) and I don't
know if it is a configuration problem or a bug.
The FreeSWITCH runs on an openvz machine and this server is not overloaded.
Before testing with trunk branch I want to share my problem looking
for help to solve it (it's in production)

I have an issue with some providers that send to my FreeSWITCH CN
packets. When this happens, the other call leg has a terrible delay
and bad quality sound.It starts with a little delay, but during the
call the delay increases more and more.

Capturing with wireshark and decoding rtp stream I can see 31% of
packets dropped by Jitter Buff in the leg in wich the delay occurs
(from FreeSWITCH IP to the other endpoint)

I don't have any problem when the provider doesn't send CN packets.

If I configure FreeSWITCH not to negotiate "comfort noise"  (profile:
supress-cng=true), the provider sends cn packets too.

I tried with no luck variables such as:

- send_silence_when_idle (with values "400" and "true")
- bridge_generate_comfort_noise=true



The rtp related params of my sofia profile are:

rtp-timer-name=soft
inbound-zrtp-passthru=false (don't use zrtp)
rtp-timeout-sec=300
rtp-hold-timeout-sec=1800
inbound-late-negotiation=true
NDLB-allow-bad-iananame=true
supress-cng=true
vad=none
t38-passthru=true
inbound-codec-prefs=PCMA,PCMU,G722,GSM
outbound-codec-prefs=PCMA,PCMU,G722,GSM

In the dialplan the only variables that I set related with rtp are:

set inherit_codec=true
export absolute_codec_string=${ep_codec_string}

Thanks in advance
--
Jose Fco. Irles Durá