diff -urN --exclude=.svn asterisk-lastjb/abstract_jb.c asterisk-jb/abstract_jb.c
--- asterisk-lastjb/abstract_jb.c	2006-02-28 17:13:17.000000000 +0100
+++ asterisk-jb/abstract_jb.c	2006-02-28 15:41:37.000000000 +0100
@@ -341,13 +341,22 @@
 		return -1;
 	}
 	
-	if(!f->has_timing_info || f->len < 2)
+	/* We consider an enabled jitterbuffer should receive frames with valid timing info. */
+	if(!f->has_timing_info || f->len < 2 || f->ts < 0)
 	{
-		/* TODO: Shouldn't we disable the jb here? Or we can produce timestamp and seqno? */
+		ast_log(LOG_WARNING, "Recieved frame with invalid timing info: "
+			"has_timing_info=%d, len=%ld, ts=%ld\n", f->has_timing_info, f->len, f->ts);
 		return -1;
 	}
 	
-	frr = ast_frisolate(f);
+	if(f->mallocd & AST_MALLOCD_HDR)
+	{
+		frr = ast_frdup(f);
+	}
+	else
+	{
+		frr = ast_frisolate(f);
+	}
 	if(frr == NULL)
 	{
 		ast_log(LOG_ERROR, "Failed to isolate frame for the jitterbuffer on channel '%s'\n", chan->name);
diff -urN --exclude=.svn asterisk-lastjb/scx_jitterbuf.c asterisk-jb/scx_jitterbuf.c
--- asterisk-lastjb/scx_jitterbuf.c	2006-02-28 17:13:17.000000000 +0100
+++ asterisk-jb/scx_jitterbuf.c	2006-02-28 15:41:37.000000000 +0100
@@ -305,8 +305,6 @@
 
 int scx_jb_get(struct scx_jb *jb, struct scx_jb_frame *frame, long now, long interpl)
 {
-	long halflen;
-	
 	assert(now >= 0);
 	assert(interpl >= 2);
 	
@@ -326,10 +324,8 @@
 		return SCX_JB_INTERP;
 	}
 	
-	halflen = (long) ((double) jb->frames->ms / 2.0);
-	
 	/* Isn't it too late for the first frame available in the jb? */
-	if(now > jb->frames->delivery + halflen)
+	if(now > jb->frames->delivery + jb->frames->ms)
 	{
 		/* yes - should drop this frame and update next to point the next frame (get_jb_head() does it) */
 		get_jb_head(jb, frame);
@@ -338,7 +334,7 @@
 	}
 	
 	/* isn't it too early to play the first frame available? */
-	if(now < jb->frames->delivery  - halflen)
+	if(now < jb->frames->delivery)
 	{
 		/* yes - should interpolate one frame */
 		/* update next */