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From: | Simon Morlat |
Subject: | Re: [Linphone-users] ortp: RTP Data Header Validity Checks |
Date: | Thu, 14 May 2009 16:32:01 +0200 |
User-agent: | KMail/1.11.2 (Linux/2.6.29-1-amd64; KDE/4.2.2; x86_64; ; ) |
Hi, Concerning the timestamp fix, you are right. I think I never saw this bug because I called rtp_session_resync() within the ssrc-changed callback. I've added this line into my svn tree, it will be commited soon. > Hi, > > i have a question to validity checks after sender change its SSRC. Ortp > discarts SSRC_CHANGED_THRESHOLD RTP Pakets till declaring source as valid. > In RFC 3550 is a code snippet with MIN_SEQUENTIAL set to 2. > SSRC_CHANGED_THRESHOLD is set to 50 Pakets. What is the reason for such a > high value (in Time it's 1s)? > > And there ist possibly a bug in validity check. Sender sends following RTP > stream: SSRC:a;Seq: b;Time: c > SSRC:a;Seq: b+1;Time: c+160 > SSRC:a;Seq: b+2;Time: c+320 > ... > SSRC:a;Seq: b+k;Time: c+(k*160) > now sender change it SSRC, Seq and Time > SSRC:x;Seq: y;Time: z > SSRC:x;Seq: y+1;Time: z+160 > SSRC:x;Seq: y+2;Time: z+320 > > if z ist lower than c+(k*160), all RTP Pakets will be discarded till sender > sends RTP Paket with Timestamp higher than c+(k*160). I think after SSRC is > decrared as valid, Timestamp should be set to current RTP Paket Timestamp. > Something like this (rtpparce.c in version 15): > > *************** > *** 148,153 **** > --- 148,154 ---- > } > > session->rcv.ssrc=rtp->ssrc; > + session->rtp.rcv_last_ts = rtp->timestamp; > > rtp_signal_table_emit(&session->on_ssrc_changed); }else{ > /*discard the packet*/ > *************** > > BR > Rudi > > > _______________________________________________ > Linphone-users mailing list > address@hidden > http://lists.nongnu.org/mailman/listinfo/linphone-users |
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