It's the optional 'encoding parameters' field. For audio channels, this is the number of channels. So /1 means 1 channel (mono) which for G729 is just fine.

-Steve


On 22 September 2010 21:14, Sergey Okhapkin <sos@sokhapkin.dyndns.org> wrote:
a=rtpmap:18 G729/8000/1

Seems to me wrong. What is /1?

On Wednesday 22 September 2010, Frank Ochere wrote:
> Hello,
>
>
>
> I've been seeing the error below for calls sent to a particular SIP
>  gateway, anyone knows what it means and should I be concerned?
>
> (I use g729 for my inbound and outbound codec prefs in FS)
>
>
>
> 2010-09-22 10:34:23.398832 [ERR] sofia.c:4919 Codec Error! v=0
>
> o=00345254725065043 1285213687 1285213687 IN IP4 1.1.1.1
>
> s=AddPac Gateway SDP
>
> c=IN IP4 1.1.1.1
>
> t=1285213687 0
>
> m=audio 24686 RTP/AVP 18
>
> a=rtpmap:18 G729/8000/1
>
> a=recvonly
>
> a=ptime:20
>
>
>
> Kind Regards
>
>
>
> Frank Ochere
>