[Iaxclient-devel] Bugfix in libiax2

[Steve K. <st...@st...>]

Iaxclient-developers,

    We just fixed a bug we found in libiax2, which caused it to never 
send full voice frames.  The basic problem is that the logic to check to 
see if we should send a full frame basically looks to see if the top 
half of the timestamp has changed, but it wasn't using the timestamp of 
the previous frame for the comparison, it was using the timestamp of the 
current frame.  Therefore, the top half will always be equal, and full 
frames will never be sent.

    I'm not sure how this affects some of the problems that people were 
having with transferred calls, but it causes havoc to the jitterbuffer 
mechanism on asterisk servers.  This will likely screw up any calls to 
an asterisk server which has the jitterbuffer enabled (which is no 
longer the default, but seems pretty important for most internet calls).

    The patch is below, and has been committed to sourceforge CVS.

    Mark:  Please also apply this to digium libiax2 CVS if it looks 
correct to you.

-SteveK


Log Message:
calc_timestamp modifies pvt->lastsent.  Therefore, the next test is always true, (since ts will ==
lastsent), and we'll never send full audio frames.

If we don't send full audio frames, we quickly screw up the jitterbuffer mechanism on the receiving
asterisk server, because the timestamp wraps, and nothing ever corrects it.

This fix follows the way this section of code works in chan_iax2.c

-SK/JO



Index: iax.c
===================================================================
RCS file: /cvsroot/iaxclient/iaxclient/lib/libiax2/src/iax.c,v
retrieving revision 1.13
retrieving revision 1.14
diff -u -d -r1.13 -r1.14
--- iax.c	13 Feb 2004 22:20:01 -0000	1.13
+++ iax.c	20 Feb 2004 22:26:51 -0000	1.14
@@ -631,9 +631,12 @@
 		return -1;
 	}
 	
+	/* this must come before the next call to calc_timestamp() since
+	 calc_timestamp() will change lastsent to the returned value */
+	lastsent = pvt->lastsent;
+
 	/* Calculate actual timestamp */
 	fts = calc_timestamp(pvt, ts);
-	lastsent = pvt->lastsent;
 
 	if (((fts & 0xFFFF0000L) == (lastsent & 0xFFFF0000L))
 		/* High two bits are the same on timestamp, or sending on a trunk */ &&