--- chan_sip.c	2006-02-13 14:58:52.768542984 +0200
+++ chan_sip.c.geop	2006-02-23 15:34:55.723163288 +0200
@@ -4521,6 +4521,22 @@
 	respprep(&resp, p, msg, req);
 	if (p->rtp) {
 		ast_rtp_offered_from_local(p->rtp, 0);
+
+//////////////////////////////////////////////////////////////////
+		char *codec=pbx_builtin_getvar_helper(p->owner,"SIP_CODEC");
+		if (codec) {
+			int fmt=ast_getformatbyname(codec);
+			if (fmt) {
+				ast_log(LOG_NOTICE, "Changing codec to '%s' for this call because of ${SIP_CODEC) variable\n",codec);
+				if (p->jointcapability & fmt) {
+					p->jointcapability &= fmt;
+					p->capability &= fmt;
+				} else
+					ast_log(LOG_NOTICE, "Ignoring ${SIP_CODEC} variable because it is not shared by both ends.\n");
+			} else ast_log(LOG_NOTICE, "Ignoring ${SIP_CODEC} variable because of unrecognized/not configured codec (check allow/disallow in sip.conf): %s\n",codec);
+		}
+/////////////////////////////////////////////////////////////////
+
 		add_sdp(&resp, p);
 	} else {
 		ast_log(LOG_ERROR, "Can't add SDP to response, since we have no RTP session allocated. Call-ID %s\n", p->callid);