diff --git a/lib_com/options.h b/lib_com/options.h
index 4156782ca3614b8f74f5e8737113ffe6c679af65..7a60330ace8187340d31cb171b63e517b7cd5d26 100755
--- a/lib_com/options.h
+++ b/lib_com/options.h
@@ -218,6 +218,7 @@
 
 #define MASA_AND_OBJECTS                                /* Nokia: Combination of MASA and objects */
 #define FIX_653_BUG_IN_SKIP_MATRIX                      /* Dlb: fix for issue #653, bug in the ivas_spar_get_skip_mat function*/
+#define FIX_663_PARAM_ISM_EXT                           /* FhG: Issue 663: ParamISM EXT output improvement */
 
 
 /* ################## End BE DEVELOPMENT switches ######################### */
diff --git a/lib_dec/ivas_ism_param_dec.c b/lib_dec/ivas_ism_param_dec.c
index b64c52bc7184f1bdba67ee0227351ad1a35cc88d..06283748dcf0735532f007ec4e86daf222629dcc 100644
--- a/lib_dec/ivas_ism_param_dec.c
+++ b/lib_dec/ivas_ism_param_dec.c
@@ -839,6 +839,7 @@ void ivas_param_ism_dec(
             }
         }
 
+#ifndef FIX_663_PARAM_ISM_EXT
         for ( i = 0; i < nchan_transport; i++ )
         {
             for ( j = 0; j < nchan_out_woLFE; j++ )
@@ -853,6 +854,29 @@ void ivas_param_ism_dec(
                 }
             }
         }
+#else
+        for ( j = 0; j < nchan_out_woLFE; j++ )
+        {
+            if ( hDirAC->azimuth_values[j] > 0.0f )
+            {
+                hDirAC->hParamIsmRendering->proto_matrix[j] = 1.0f;
+                hDirAC->hParamIsmRendering->proto_matrix[nchan_out_woLFE + j] = 0.0f;
+            }
+            else
+            {
+                if ( hDirAC->azimuth_values[j] < 0.0f )
+                {
+                    hDirAC->hParamIsmRendering->proto_matrix[j] = 0.0f;
+                    hDirAC->hParamIsmRendering->proto_matrix[nchan_out_woLFE + j] = 1.0f;
+                }
+                else /* == 0.0f */
+                {
+                    hDirAC->hParamIsmRendering->proto_matrix[j] = 0.5f;
+                    hDirAC->hParamIsmRendering->proto_matrix[nchan_out_woLFE + j] = 0.5f;
+                }
+            }
+        }
+#endif
     }
 
     /* Energy Compensation */
@@ -1193,6 +1217,7 @@ void ivas_param_ism_dec_digest_tc(
             }
         }
 
+#ifndef FIX_663_PARAM_ISM_EXT
         for ( i = 0; i < nchan_transport; i++ )
         {
             for ( j = 0; j < nchan_out_woLFE; j++ )
@@ -1207,6 +1232,29 @@ void ivas_param_ism_dec_digest_tc(
                 }
             }
         }
+#else
+        for ( j = 0; j < nchan_out_woLFE; j++ )
+        {
+            if ( hDirAC->azimuth_values[j] > 0.0f )
+            {
+                hDirAC->hParamIsmRendering->proto_matrix[j] = 1.0f;
+                hDirAC->hParamIsmRendering->proto_matrix[nchan_out_woLFE + j] = 0.0f;
+            }
+            else
+            {
+                if ( hDirAC->azimuth_values[j] < 0.0f )
+                {
+                    hDirAC->hParamIsmRendering->proto_matrix[j] = 0.0f;
+                    hDirAC->hParamIsmRendering->proto_matrix[nchan_out_woLFE + j] = 1.0f;
+                }
+                else /* == 0.0f */
+                {
+                    hDirAC->hParamIsmRendering->proto_matrix[j] = 0.5f;
+                    hDirAC->hParamIsmRendering->proto_matrix[nchan_out_woLFE + j] = 0.5f;
+                }
+            }
+        }
+#endif
     }
 
     /* Energy Compensation */