set isac default ptime to 30

src/switch_core.c

@@ -1730,6 +1730,7 @@ static void switch_load_core_config(const char *file)
 	switch_xml_t xml = NULL, cfg = NULL;
 
 	switch_core_hash_insert(runtime.ptimes, "ilbc", &d_30);
+	switch_core_hash_insert(runtime.ptimes, "isac", &d_30);
 	switch_core_hash_insert(runtime.ptimes, "G723", &d_30);
 
 	if ((xml = switch_xml_open_cfg(file, &cfg, NULL))) {