Index: channels/chan_sip.c
===================================================================
--- channels/chan_sip.c	(Revision 242356)
+++ channels/chan_sip.c	(Arbeitskopie)
@@ -1770,6 +1770,7 @@
 	unsigned int reqsipoptions;		/*!< Required SIP options on the other end */
 	struct ast_codec_pref prefs;		/*!< codec prefs */
 	format_t capability;				/*!< Special capability (codec) */
+	format_t dynamic_t38_capability;	/*!< Switch T.38 on/off from dialplan */ 
 	format_t jointcapability;			/*!< Supported capability at both ends (codecs) */
 	format_t peercapability;			/*!< Supported peer capability */
 	format_t prefcodec;				/*!< Preferred codec (outbound only) */
@@ -2490,6 +2491,7 @@
 
 /*--- Codec handling / SDP */
 static void try_suggested_sip_codec(struct sip_pvt *p);
+static void dynamic_switch_t38(struct sip_pvt *p);
 static const char *get_sdp_iterate(int* start, struct sip_request *req, const char *name);
 static char get_sdp_line(int *start, int stop, struct sip_request *req, const char **value);
 static int find_sdp(struct sip_request *req);
@@ -6492,6 +6494,25 @@
 	return;	
 }
 
+/*! \brief Set T.38 on/off from dialplan using the T.38_SWITCH channel variable */
+static void dynamic_switch_t38(struct sip_pvt *p)
+{
+	const char *t38_state;
+
+	p->dynamic_t38_capability = 1;
+	t38_state = pbx_builtin_getvar_helper(p->owner, "T.38_SWITCH");
+	
+	if (!t38_state) 
+		return;
+	
+	if(strcmp(t38_state, "off") == 0) {
+		ast_log(LOG_NOTICE, "Changing T.38 state to '%s' for this call because of ${T.38_SWITCH} variable\n", t38_state);
+		p->dynamic_t38_capability = 0;
+	}
+	
+	return;	
+}
+
 /*! \brief  sip_answer: Answer SIP call , send 200 OK on Invite
  * Part of PBX interface */
 static int sip_answer(struct ast_channel *ast)
@@ -8484,8 +8505,8 @@
 			ast_log(LOG_DEBUG, "Processing session-level SDP %c=%s... %s\n", type, value, (processed == TRUE)? "OK." : "UNSUPPORTED.");
  	}
 
+	dynamic_switch_t38(p);
 
-
 	/* Scan media stream (m=) specific parameters loop */
 	while (!ast_strlen_zero(nextm)) {
 		int audio = FALSE;
@@ -8565,7 +8586,7 @@
 				ast_rtp_codecs_payloads_set_m_type(&newtextrtp, NULL, codec);
 			}
 		/* Search for image media definition */
-		} else if (p->udptl && ((sscanf(m, "image %30d udptl t38%n", &x, &len) == 1 && len > 0) ||
+		} else if (p->dynamic_t38_capability != 0 && p->udptl && ((sscanf(m, "image %30d udptl t38%n", &x, &len) == 1 && len > 0) ||
 					(sscanf(m, "image %30d UDPTL t38%n", &x, &len) == 1 && len > 0) )) {
 			image = TRUE;
 			if (debug)