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[Linphone-users] ortp: RTP Data Header Validity Checks
From: |
Rudolf Svanda |
Subject: |
[Linphone-users] ortp: RTP Data Header Validity Checks |
Date: |
Thu, 14 May 2009 08:19:21 +0200 |
User-agent: |
KMail/1.9.10 |
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] ortp: RTP Data Header Validity Checks,
Rudolf Svanda <=