Re: [Linphone-developers] oRTP pb during SIP refresh

[Simon Morlat]

Hi Frederik,

I understand the problem, and I agree it's a bug for many people.
Now the problem with your patch is that it simply disables the RTP
session locking feature. You could rather remove the entire 20-30 lines
of code.
I cannot accept a patch that removes a feature that was required by
other people in the past.
A better approach (to me) would to render the SSRC_CHANGED_THRESHOLD
configurable, through an api call, so that we can meet everybody's
requirements.
In linphone you have
rtp_session_signal_connect(rtpr,"ssrc_changed",(RtpCallback)rtp_session_resync,(long)NULL);
so that when the ssrc change is notified, the SYNC flag is set again.
So if you set the SSRC changed threshold lets say to 0, it will work
perfectly.

I just commited to git a small patch to implement this:

Author: Simon Morlat <address@hidden>  2010-01-21 11:49:14
Committer: Simon Morlat <address@hidden>  2010-01-21 11:49:14
Parent: 5679b02d5a4cf4de680a4bf37ab620935041d2d1 (add missing
declarations in linphonecore.h)
Branches: master, remotes/origin/master, remotes/private/master
Follows: 
Precedes: 

    set ssrc_changed_thres to 0


Simon



Le jeudi 21 janvier 2010 à 10:22 +0100, Frédérik Rouleau a écrit :
> Hi Simon,
> 
> I cannot see why my patch is a problem. You are still locked to a
> stream, it just enable to switch faster on a new stream when you ask
> oRTP to.
> Linphone has the same problem, at each refresh, you have a 1 second
> silence (50 * 20ms). The gateway is a Cirpack, the same equipement
> used by Free operator in France. Might be difficult to have any
> upgrade on that side !!!
> You also have this problem during ringing, when you answer the call,
> the RTP stream is reset by the Cirpack, then you also have a 1 s
> silence !
> I am looking for a way to solve this issues. If you have better
> suggestion, I am open to any proposal.
> 
> Regards,
> 
> Frédérik
> 
> 
> 2010/1/19 Simon Morlat <address@hidden>
>         Hi Frédérik,
>         
>         I understand this change solves your problem, but it is not
>         really
>         compatible with what this SSRC checking was done for.
>         Initially the goal was to lock on the initial stream (and
>         discard any
>         others), and when one stream appears to be active (50 packet
>         received
>         without any other SSRC in between), we lock to this new
>         stream.
>         I think the gateway should not reinit the seq and timestamp
>         numbers.
>         
>         RFC4028 was implemented in linphone quite recently. If you
>         have both
>         last svn/git of linphone and last svn of eXosip2, and have
>         use_session_timers=1 in the [sip] section of the .linphonerc
>         config
>         file, they are enabled.
>         
>         Try it, this may workaround the gateway behaviour.
>         
>         Simon
>         
>         Le mardi 12 janvier 2010 à 16:03 +0100, Frédérik Rouleau a
>         écrit :
>         
>         > Hello all,
>         >
>         > I am using oRTP and a SIP gateway which support SIP REFRESH
>         (RFC
>         > 4028). So at a fixed interval (600 s) I receive a SIP UPDATE
>         but the
>         > gateway also reinit the SSRC et seq number of the RTP flow.
>         > The problem is that oRTP waits 1 second before it sends
>         SSRC_CHANGED
>         > message and during that ime I am loosing RTP paquets.
>         Looking into the
>         > code shows that there is a constant SSRC_CHANGED_THRESHOLD
>         set at 50
>         > setting this delay.
>         >
>         > Reducing the threshold might have some side effects but can
>         we add a
>         > kind of SSRC_change_pending state which set the flag
>         > RTP_SESSION_RECV_SYNC on the first SSRC change paquet. for
>         example the
>         > rtp_parse code will look like:
>         >
>         >             if
>         (session->inc_same_ssrc_count>SSRC_CHANGED_THRESHOLD){
>         >
>         >                 /* store the sender rtp address to do
>         symmetric RTP */
>         >                 if (!session->use_connect){
>         >                     if (session->rtp.socket>0 &&
>         > session->symmetric_rtp){
>         >                         /* store the sender rtp address to
>         do
>         > symmetric RTP */
>         >
>         memcpy(&session->rtp.rem_addr,addr,addrlen);
>         >                         session->rtp.rem_addrlen=addrlen;
>         >                     }
>         >                 }
>         >                 session->rtp.rcv_last_ts = rtp->timestamp;
>         >                 session->rcv.ssrc=rtp->ssrc;
>         >
>         rtp_signal_table_emit(&session->on_ssrc_changed);
>         >             }else if (session->ssrc_change_pending){
>         >                 session->ssrc_change_pending=FALSE;
>         >                 rtp_session_set_flag(session,
>         RTP_SESSION_RECV_SYNC);
>         >             }else{
>         >                 /*discard the packet*/
>         >                 ortp_debug("Receiving packet with unknown
>         ssrc.");
>         >                 stats->bad++;
>         >                 ortp_global_stats.bad++;
>         >                 freemsg(mp);
>         >                 return;
>         >             }
>         >
>         > What do you think about it ? If you agree I can make changes
>         and
>         > propose a patch.
>         >
>         > Regards,
>         >
>         >
>         
>         > _______________________________________________
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>         
>         
>