diff --git a/aom/aomcx.h b/aom/aomcx.h
index 53bdc1e..f275890 100644
--- a/aom/aomcx.h
+++ b/aom/aomcx.h
@@ -1677,10 +1677,10 @@
 
 /*!brief Parameters for setting ref frame config */
 typedef struct aom_svc_ref_frame_config {
-  // 7 references: LAST_FRAME (0), LAST2_FRAME(1), LAST3_FRAME(2),
-  // GOLDEN_FRAME(3), BWDREF_FRAME(4), ALTREF2_FRAME(5), ALTREF_FRAME(6).
+  // 7 references: The index 0 - 6 refers to the references:
+  // last(0), last2(1), last3(2), golden(3), bwdref(4), altref2(5), altref(6).
   int reference[7]; /**< Reference flag for each of the 7 references. */
-  /*! Buffer slot index for each of 7 references. */
+  /*! Buffer slot index for each of 7 references indexed above. */
   int ref_idx[7];
   int refresh[8]; /**< Refresh flag for each of the 8 slots. */
 } aom_svc_ref_frame_config_t;
diff --git a/av1/encoder/nonrd_pickmode.c b/av1/encoder/nonrd_pickmode.c
index 9b774e2..2b46559 100644
--- a/av1/encoder/nonrd_pickmode.c
+++ b/av1/encoder/nonrd_pickmode.c
@@ -1805,10 +1805,10 @@
   use_ref_frame[ALTREF_FRAME] = use_alt_ref_frame;
   use_ref_frame[GOLDEN_FRAME] = use_golden_ref_frame;
   use_ref_frame[LAST_FRAME] = use_last_ref_frame;
-  // For now keep this assert on, but we should remove it for svc mode,
-  // as the user may want to generate an intra-only frame (no inter-modes).
-  // Remove this assert in subsequent CL when nonrd_pickmode is tested for the
-  // case of intra-only frame (no references enabled).
+  // Keep this assert on, as only 3 references are used in nonrd_pickmode
+  // (LAST, GOLDEN, ALTREF), and if all 3 are not set by user then this
+  // frame must be an intra-only frame and hence should never enter the
+  // pickmode here for inter frames.
   assert(use_last_ref_frame || use_golden_ref_frame || use_alt_ref_frame);
 }
 
diff --git a/examples/svc_encoder_rtc.cc b/examples/svc_encoder_rtc.cc
index 8bae0d1..cc23dc2 100644
--- a/examples/svc_encoder_rtc.cc
+++ b/examples/svc_encoder_rtc.cc
@@ -437,10 +437,12 @@
       enc_cfg->rc_target_bitrate, enc_cfg->kf_max_dist);
 }
 
-static int mode_to_num_temporal_layers[11] = {
-  1, 2, 3, 3, 2, 1, 1, 3, 3, 3, 3
+static int mode_to_num_temporal_layers[12] = {
+  1, 2, 3, 3, 2, 1, 1, 3, 3, 3, 3, 3,
 };
-static int mode_to_num_spatial_layers[11] = { 1, 1, 1, 1, 1, 2, 3, 2, 3, 3, 3 };
+static int mode_to_num_spatial_layers[12] = {
+  1, 1, 1, 1, 1, 2, 3, 2, 3, 3, 3, 3,
+};
 
 // For rate control encoding stats.
 struct RateControlMetrics {
@@ -615,6 +617,7 @@
   int i;
   int enable_longterm_temporal_ref = 1;
   int shift = (layering_mode == 8) ? 2 : 0;
+  int simulcast_mode = (layering_mode == 11);
   *use_svc_control = 1;
   layer_id->spatial_layer_id = spatial_layer_id;
   int lag_index = 0;
@@ -1110,7 +1113,173 @@
           ref_frame_config->ref_idx[SVC_GOLDEN_FRAME] = 4;
         }
       }
-      if (layer_id->spatial_layer_id > 0) {
+      break;
+    case 11:
+      // Simulcast mode for 3 spatial and 3 temporal layers.
+      // No inter-layer predicton, only prediction is temporal and single
+      // reference (LAST).
+      // No overlap in buffer slots between spatial layers. So for example,
+      // SL0 only uses slots 0 and 1.
+      // SL1 only uses slots 2 and 3.
+      // SL2 only uses slots 4 and 5.
+      // All 7 references for each inter-frame must only access buffer slots
+      // for that spatial layer.
+      // On key (super)frames: SL1 and SL2 must have no references set
+      // and must refresh all the slots for that layer only (so 2 and 3
+      // for SL1, 4 and 5 for SL2). The base SL0 will be labelled internally
+      // as a Key frame (refresh all slots). SL1/SL2 will be labelled
+      // internally as Intra-only frames that allow that stream to be decoded.
+      // These conditions will allow for each spatial stream to be
+      // independently decodeable.
+
+      // Initialize all references to 0 (don't use reference).
+      for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+        ref_frame_config->reference[i] = 0;
+      // Initialize as no refresh/update for all slots.
+      for (i = 0; i < REF_FRAMES; i++) ref_frame_config->refresh[i] = 0;
+      for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+        ref_frame_config->ref_idx[i] = 0;
+
+      if (is_key_frame) {
+        if (layer_id->spatial_layer_id == 0) {
+          // Assign LAST/GOLDEN to slot 0/1.
+          // Refesh slots 0 and 1 for SL0.
+          // SL0: this will get set to KEY frame internally.
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 0;
+          ref_frame_config->ref_idx[SVC_GOLDEN_FRAME] = 1;
+          ref_frame_config->refresh[0] = 1;
+          ref_frame_config->refresh[1] = 1;
+        } else if (layer_id->spatial_layer_id == 1) {
+          // Assign LAST/GOLDEN to slot 2/3.
+          // Refesh slots 2 and 3 for SL1.
+          // This will get set to Intra-only frame internally.
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 2;
+          ref_frame_config->ref_idx[SVC_GOLDEN_FRAME] = 3;
+          ref_frame_config->refresh[2] = 1;
+          ref_frame_config->refresh[3] = 1;
+        } else if (layer_id->spatial_layer_id == 2) {
+          // Assign LAST/GOLDEN to slot 4/5.
+          // Refresh slots 4 and 5 for SL2.
+          // This will get set to Intra-only frame internally.
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 4;
+          ref_frame_config->ref_idx[SVC_GOLDEN_FRAME] = 5;
+          ref_frame_config->refresh[4] = 1;
+          ref_frame_config->refresh[5] = 1;
+        }
+      } else if (superframe_cnt % 4 == 0) {
+        // Base temporal layer: TL0
+        layer_id->temporal_layer_id = 0;
+        if (layer_id->spatial_layer_id == 0) {  // SL0
+          // Reference LAST. Assign all references to either slot
+          // 0 or 1. Here we assign LAST to slot 0, all others to 1.
+          // Update slot 0 (LAST).
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 1;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 0;
+          ref_frame_config->refresh[0] = 1;
+        } else if (layer_id->spatial_layer_id == 1) {  // SL1
+          // Reference LAST. Assign all references to either slot
+          // 2 or 3. Here we assign LAST to slot 2, all others to 3.
+          // Update slot 2 (LAST).
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 3;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 2;
+          ref_frame_config->refresh[2] = 1;
+        } else if (layer_id->spatial_layer_id == 2) {  // SL2
+          // Reference LAST. Assign all references to either slot
+          // 4 or 5. Here we assign LAST to slot 4, all others to 5.
+          // Update slot 4 (LAST).
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 5;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 4;
+          ref_frame_config->refresh[4] = 1;
+        }
+      } else if ((superframe_cnt - 1) % 4 == 0) {
+        // First top temporal enhancement layer: TL2
+        layer_id->temporal_layer_id = 2;
+        if (layer_id->spatial_layer_id == 0) {  // SL0
+          // Reference LAST (slot 0). Assign other references to slot 1.
+          // No update/refresh on any slots.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 1;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 0;
+        } else if (layer_id->spatial_layer_id == 1) {  // SL1
+          // Reference LAST (slot 2). Assign other references to slot 3.
+          // No update/refresh on any slots.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 3;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 2;
+        } else if (layer_id->spatial_layer_id == 2) {  // SL2
+          // Reference LAST (slot 4). Assign other references to slot 4.
+          // No update/refresh on any slots.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 5;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 4;
+        }
+      } else if ((superframe_cnt - 2) % 4 == 0) {
+        // Middle temporal enhancement layer: TL1
+        layer_id->temporal_layer_id = 1;
+        if (layer_id->spatial_layer_id == 0) {  // SL0
+          // Reference LAST (slot 0).
+          // Set GOLDEN to slot 1 and update slot 1.
+          // This will be used as reference for next TL2.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 1;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 0;
+          ref_frame_config->refresh[1] = 1;
+        } else if (layer_id->spatial_layer_id == 1) {  // SL1
+          // Reference LAST (slot 2).
+          // Set GOLDEN to slot 3 and update slot 3.
+          // This will be used as reference for next TL2.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 3;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 2;
+          ref_frame_config->refresh[3] = 1;
+        } else if (layer_id->spatial_layer_id == 2) {  // SL2
+          // Reference LAST (slot 4).
+          // Set GOLDEN to slot 5 and update slot 5.
+          // This will be used as reference for next TL2.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 5;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 4;
+          ref_frame_config->refresh[5] = 1;
+        }
+      } else if ((superframe_cnt - 3) % 4 == 0) {
+        // Second top temporal enhancement layer: TL2
+        layer_id->temporal_layer_id = 2;
+        if (layer_id->spatial_layer_id == 0) {  // SL0
+          // Reference LAST (slot 1). Assign other references to slot 0.
+          // No update/refresh on any slots.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 0;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 1;
+        } else if (layer_id->spatial_layer_id == 1) {  // SL1
+          // Reference LAST (slot 3). Assign other references to slot 2.
+          // No update/refresh on any slots.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 2;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 3;
+        } else if (layer_id->spatial_layer_id == 2) {  // SL2
+          // Reference LAST (slot 5). Assign other references to slot 4.
+          // No update/refresh on any slots.
+          ref_frame_config->reference[SVC_LAST_FRAME] = 1;
+          for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+            ref_frame_config->ref_idx[i] = 4;
+          ref_frame_config->ref_idx[SVC_LAST_FRAME] = 5;
+        }
+      }
+      if (!simulcast_mode && layer_id->spatial_layer_id > 0) {
         // Always reference GOLDEN (inter-layer prediction).
         ref_frame_config->reference[SVC_GOLDEN_FRAME] = 1;
         if (ksvc_mode) {
@@ -1128,8 +1297,8 @@
       // allow for top spatial layer to use additional temporal reference.
       // Additional reference is only updated on base temporal layer, every
       // 10 TL0 frames here.
-      if (enable_longterm_temporal_ref && layer_id->spatial_layer_id == 2 &&
-          layering_mode == 8) {
+      if (!simulcast_mode && enable_longterm_temporal_ref &&
+          layer_id->spatial_layer_id == 2 && layering_mode == 8) {
         ref_frame_config->ref_idx[SVC_ALTREF_FRAME] = REF_FRAMES - 1;
         if (!is_key_frame) ref_frame_config->reference[SVC_ALTREF_FRAME] = 1;
         if (base_count % 10 == 0 && layer_id->temporal_layer_id == 0)
@@ -1710,10 +1879,14 @@
       frame_cnt_layer[layer] += 1;
 
       got_data = 0;
+      // For simulcast (mode 11): write out each spatial layer to the file.
+      int ss_layers_write = (app_input.layering_mode == 11)
+                                ? layer_id.spatial_layer_id + 1
+                                : ss_number_layers;
       while ((pkt = aom_codec_get_cx_data(&codec, &iter))) {
         switch (pkt->kind) {
           case AOM_CODEC_CX_FRAME_PKT:
-            for (int sl = layer_id.spatial_layer_id; sl < ss_number_layers;
+            for (int sl = layer_id.spatial_layer_id; sl < ss_layers_write;
                  ++sl) {
               for (int tl = layer_id.temporal_layer_id; tl < ts_number_layers;
                    ++tl) {
diff --git a/test/svc_datarate_test.cc b/test/svc_datarate_test.cc
index d99d6a3..04f2fd7 100644
--- a/test/svc_datarate_test.cc
+++ b/test/svc_datarate_test.cc
@@ -94,6 +94,7 @@
     rps_recovery_frame_ = 0;
     user_define_frame_qp_ = 0;
     set_speed_per_layer_ = false;
+    simulcast_mode_ = false;
   }
 
   virtual void PreEncodeFrameHook(::libaom_test::VideoSource *video,
@@ -144,7 +145,7 @@
         video->frame(), &layer_id_, &ref_frame_config_, &ref_frame_comp_pred_,
         spatial_layer_id, multi_ref_, comp_pred_,
         (video->frame() % cfg_.kf_max_dist) == 0, dynamic_enable_disable_mode_,
-        rps_mode_, rps_recovery_frame_);
+        rps_mode_, rps_recovery_frame_, simulcast_mode_);
     if (intra_only_ == 1 && frame_sync_ > 0) {
       // Set an Intra-only frame on SL0 at frame_sync_.
       // In order to allow decoding to start on SL0 in mid-sequence we need to
@@ -254,6 +255,15 @@
       last_pts_ = pkt->data.frame.pts;
       superframe_cnt_++;
     }
+    // For simulcast mode: verify that for first frame to start decoding,
+    // for SL > 0, are Intra-only frames (not Key), whereas SL0 is Key.
+    if (simulcast_mode_ && superframe_cnt_ == (int)frame_to_start_decoding_) {
+      if (layer_id_.spatial_layer_id > 0) {
+        EXPECT_NE(pkt->data.frame.flags & AOM_FRAME_IS_KEY, AOM_FRAME_IS_KEY);
+      } else if (layer_id_.spatial_layer_id == 0) {
+        EXPECT_EQ(pkt->data.frame.flags & AOM_FRAME_IS_KEY, AOM_FRAME_IS_KEY);
+      }
+    }
   }
 
   virtual void EndPassHook() {
@@ -279,6 +289,11 @@
       if (layer_to_decode_ == 0 && frame_sync_ > 0 &&
           (layer_frame_cnt_ - 1) % 3 != 0)
         return 0;
+    } else if (simulcast_mode_) {
+      // Only start decoding at frames_to_start_decoding_ and only
+      // for top spatial layer SL2 (layer_to_decode_).
+      if (current_video_frame_ < frame_to_start_decoding_) return 0;
+      if (layer_id_.spatial_layer_id < (int)layer_to_decode_) return 0;
     }
     return 1;
   }
@@ -345,13 +360,301 @@
     }
   }
 
+  // Simulcast mode for 3 spatial and 3 temporal layers.
+  // No inter-layer predicton, only prediction is temporal and single
+  // reference (LAST).
+  // No overlap in buffer slots between spatial layers. So for example,
+  // SL0 only uses slots 0 and 1.
+  // SL1 only uses slots 2 and 3.
+  // SL2 only uses slots 4 and 5.
+  // All 7 references for each inter-frame must only access buffer slots
+  // for that spatial layer.
+  // On key (super)frames: SL1 and SL2 must have no references set
+  // and must refresh all the slots for that layer only (so 2 and 3
+  // for SL1, 4 and 5 for SL2). The base SL0 will be labelled internally
+  // as a Key frame (refresh all slots). SL1/SL2 will be labelled
+  // internally as Intra-only frames that allow that stream to be decoded.
+  // These conditions will allow for each spatial stream to be
+  // independently decodeable.
+  static void ref_config_simulcast3SL3TL(
+      aom_svc_ref_frame_config_t *ref_frame_config,
+      aom_svc_layer_id_t *layer_id, int is_key_frame, int superframe_cnt) {
+    int i;
+    // Initialize all references to 0 (don't use reference).
+    for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+      ref_frame_config->reference[i] = 0;
+    // Initialize as no refresh/update for all slots.
+    for (i = 0; i < REF_FRAMES; i++) ref_frame_config->refresh[i] = 0;
+    for (i = 0; i < INTER_REFS_PER_FRAME; i++) ref_frame_config->ref_idx[i] = 0;
+
+    if (is_key_frame) {
+      if (layer_id->spatial_layer_id == 0) {
+        // Assign LAST/GOLDEN to slot 0/1.
+        // Refesh slots 0 and 1 for SL0.
+        // SL0: this will get set to KEY frame internally.
+        ref_frame_config->ref_idx[0] = 0;
+        ref_frame_config->ref_idx[3] = 1;
+        ref_frame_config->refresh[0] = 1;
+        ref_frame_config->refresh[1] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {
+        // Assign LAST/GOLDEN to slot 2/3.
+        // Refesh slots 2 and 3 for SL1.
+        // This will get set to Intra-only frame internally.
+        ref_frame_config->ref_idx[0] = 2;
+        ref_frame_config->ref_idx[3] = 3;
+        ref_frame_config->refresh[2] = 1;
+        ref_frame_config->refresh[3] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {
+        // Assign LAST/GOLDEN to slot 4/5.
+        // Refresh slots 4 and 5 for SL2.
+        // This will get set to Intra-only frame internally.
+        ref_frame_config->ref_idx[0] = 4;
+        ref_frame_config->ref_idx[3] = 5;
+        ref_frame_config->refresh[4] = 1;
+        ref_frame_config->refresh[5] = 1;
+      }
+    } else if (superframe_cnt % 4 == 0) {
+      // Base temporal layer: TL0
+      layer_id->temporal_layer_id = 0;
+      if (layer_id->spatial_layer_id == 0) {  // SL0
+        // Reference LAST. Assign all references to either slot
+        // 0 or 1. Here we assign LAST to slot 0, all others to 1.
+        // Update slot 0 (LAST).
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 1;
+        ref_frame_config->ref_idx[0] = 0;
+        ref_frame_config->refresh[0] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {  // SL1
+        // Reference LAST. Assign all references to either slot
+        // 2 or 3. Here we assign LAST to slot 2, all others to 3.
+        // Update slot 2 (LAST).
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 3;
+        ref_frame_config->ref_idx[0] = 2;
+        ref_frame_config->refresh[2] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {  // SL2
+        // Reference LAST. Assign all references to either slot
+        // 4 or 5. Here we assign LAST to slot 4, all others to 5.
+        // Update slot 4 (LAST).
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 5;
+        ref_frame_config->ref_idx[0] = 4;
+        ref_frame_config->refresh[4] = 1;
+      }
+    } else if ((superframe_cnt - 1) % 4 == 0) {
+      // First top temporal enhancement layer: TL2
+      layer_id->temporal_layer_id = 2;
+      if (layer_id->spatial_layer_id == 0) {  // SL0
+        // Reference LAST (slot 0). Assign other references to slot 1.
+        // No update/refresh on any slots.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 1;
+        ref_frame_config->ref_idx[0] = 0;
+      } else if (layer_id->spatial_layer_id == 1) {  // SL1
+        // Reference LAST (slot 2). Assign other references to slot 3.
+        // No update/refresh on any slots.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 3;
+        ref_frame_config->ref_idx[0] = 2;
+      } else if (layer_id->spatial_layer_id == 2) {  // SL2
+        // Reference LAST (slot 4). Assign other references to slot 4.
+        // No update/refresh on any slots.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 5;
+        ref_frame_config->ref_idx[0] = 4;
+      }
+    } else if ((superframe_cnt - 2) % 4 == 0) {
+      // Middle temporal enhancement layer: TL1
+      layer_id->temporal_layer_id = 1;
+      if (layer_id->spatial_layer_id == 0) {  // SL0
+        // Reference LAST (slot 0).
+        // Set GOLDEN to slot 1 and update slot 1.
+        // This will be used as reference for next TL2.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 1;
+        ref_frame_config->ref_idx[0] = 0;
+        ref_frame_config->refresh[1] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {  // SL1
+        // Reference LAST (slot 2).
+        // Set GOLDEN to slot 3 and update slot 3.
+        // This will be used as reference for next TL2.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 3;
+        ref_frame_config->ref_idx[0] = 2;
+        ref_frame_config->refresh[3] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {  // SL2
+        // Reference LAST (slot 4).
+        // Set GOLDEN to slot 5 and update slot 5.
+        // This will be used as reference for next TL2.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 5;
+        ref_frame_config->ref_idx[0] = 4;
+        ref_frame_config->refresh[5] = 1;
+      }
+    } else if ((superframe_cnt - 3) % 4 == 0) {
+      // Second top temporal enhancement layer: TL2
+      layer_id->temporal_layer_id = 2;
+      if (layer_id->spatial_layer_id == 0) {  // SL0
+        // Reference LAST (slot 1). Assign other references to slot 0.
+        // No update/refresh on any slots.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[0] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {  // SL1
+        // Reference LAST (slot 3). Assign other references to slot 2.
+        // No update/refresh on any slots.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 2;
+        ref_frame_config->ref_idx[0] = 3;
+      } else if (layer_id->spatial_layer_id == 2) {  // SL2
+        // Reference LAST (slot 5). Assign other references to slot 4.
+        // No update/refresh on any slots.
+        ref_frame_config->reference[0] = 1;
+        for (i = 0; i < INTER_REFS_PER_FRAME; i++)
+          ref_frame_config->ref_idx[i] = 4;
+        ref_frame_config->ref_idx[0] = 5;
+      }
+    }
+  }
+
+  // 3 spatial and 3 temporal layer.
+  // Overlap in the buffer slot updates: the slots 3 and 4 updated by
+  // first TL2 are reused for update in TL1 superframe.
+  static void ref_config_3SL3TL(aom_svc_ref_frame_config_t *ref_frame_config,
+                                aom_svc_layer_id_t *layer_id, int is_key_frame,
+                                int superframe_cnt) {
+    if (superframe_cnt % 4 == 0) {
+      // Base temporal layer.
+      layer_id->temporal_layer_id = 0;
+      if (layer_id->spatial_layer_id == 0) {
+        // Reference LAST, update LAST.
+        // Set all buffer_idx to 0.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->refresh[0] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 1,
+        // GOLDEN (and all other refs) to slot 0.
+        // Update slot 1 (LAST).
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[0] = 1;
+        ref_frame_config->refresh[1] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 2,
+        // GOLDEN (and all other refs) to slot 1.
+        // Update slot 2 (LAST).
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 1;
+        ref_frame_config->ref_idx[0] = 2;
+        ref_frame_config->refresh[2] = 1;
+      }
+    } else if ((superframe_cnt - 1) % 4 == 0) {
+      // First top temporal enhancement layer.
+      layer_id->temporal_layer_id = 2;
+      if (layer_id->spatial_layer_id == 0) {
+        // Reference LAST (slot 0).
+        // Set GOLDEN to slot 3 and update slot 3.
+        // Set all other buffer_idx to slot 0.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[3] = 3;
+        ref_frame_config->refresh[3] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 1,
+        // GOLDEN (and all other refs) to slot 3.
+        // Set LAST2 to slot 4 and Update slot 4.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 3;
+        ref_frame_config->ref_idx[0] = 1;
+        ref_frame_config->ref_idx[1] = 4;
+        ref_frame_config->refresh[4] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 2,
+        // GOLDEN (and all other refs) to slot 4.
+        // No update.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 4;
+        ref_frame_config->ref_idx[0] = 2;
+      }
+    } else if ((superframe_cnt - 2) % 4 == 0) {
+      // Middle temporal enhancement layer.
+      layer_id->temporal_layer_id = 1;
+      if (layer_id->spatial_layer_id == 0) {
+        // Reference LAST.
+        // Set all buffer_idx to 0.
+        // Set GOLDEN to slot 3 and update slot 3.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[3] = 3;
+        ref_frame_config->refresh[3] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 1,
+        // GOLDEN (and all other refs) to slot 3.
+        // Set LAST2 to slot 4 and update slot 4.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 3;
+        ref_frame_config->ref_idx[0] = 1;
+        ref_frame_config->ref_idx[2] = 4;
+        ref_frame_config->refresh[4] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 2,
+        // GOLDEN (and all other refs) to slot 4.
+        // Set LAST2 to slot 5 and update slot 5.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 4;
+        ref_frame_config->ref_idx[0] = 2;
+        ref_frame_config->ref_idx[2] = 5;
+        ref_frame_config->refresh[5] = 1;
+      }
+    } else if ((superframe_cnt - 3) % 4 == 0) {
+      // Second top temporal enhancement layer.
+      layer_id->temporal_layer_id = 2;
+      if (layer_id->spatial_layer_id == 0) {
+        // Set LAST to slot 3 and reference LAST.
+        // Set GOLDEN to slot 3 and update slot 3.
+        // Set all other buffer_idx to 0.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[0] = 3;
+        ref_frame_config->ref_idx[3] = 3;
+        ref_frame_config->refresh[3] = 1;
+      } else if (layer_id->spatial_layer_id == 1) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 4,
+        // GOLDEN to slot 3. Set LAST2 to slot 4 and update slot 4.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[0] = 4;
+        ref_frame_config->ref_idx[3] = 3;
+        ref_frame_config->ref_idx[1] = 4;
+        ref_frame_config->refresh[4] = 1;
+      } else if (layer_id->spatial_layer_id == 2) {
+        // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 5,
+        // GOLDEN to slot 4. No update.
+        for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
+        ref_frame_config->ref_idx[0] = 5;
+        ref_frame_config->ref_idx[3] = 4;
+      }
+    }
+    if (layer_id->spatial_layer_id > 0) {
+      // Always reference GOLDEN (inter-layer prediction).
+      ref_frame_config->reference[3] = 1;
+      if (is_key_frame && layer_id->spatial_layer_id > 0) {
+        // On superframes whose base is key: remove LAST since GOLDEN
+        // is used as reference.
+        ref_frame_config->reference[0] = 0;
+      }
+    }
+  }
+
   // Layer pattern configuration.
   virtual int set_layer_pattern(
       int frame_cnt, aom_svc_layer_id_t *layer_id,
       aom_svc_ref_frame_config_t *ref_frame_config,
       aom_svc_ref_frame_comp_pred_t *ref_frame_comp_pred, int spatial_layer,
       int multi_ref, int comp_pred, int is_key_frame,
-      int dynamic_enable_disable_mode, int rps_mode, int rps_recovery_frame) {
+      int dynamic_enable_disable_mode, int rps_mode, int rps_recovery_frame,
+      int simulcast_mode) {
     int lag_index = 0;
     int base_count = frame_cnt >> 2;
     layer_id->spatial_layer_id = spatial_layer;
@@ -506,128 +809,21 @@
       // Reference GOLDEN.
       if (layer_id->spatial_layer_id > 0) ref_frame_config->reference[3] = 1;
     } else if (number_temporal_layers_ == 3 && number_spatial_layers_ == 3) {
-      // 3 spatial and 3 temporal layer.
-      // Overlap in the buffer slot updates: the slots 3 and 4 updated by
-      // first TL2 are reused for update in TL1 superframe.
-      if (superframe_cnt_ % 4 == 0) {
-        // Base temporal layer.
-        layer_id->temporal_layer_id = 0;
-        if (layer_id->spatial_layer_id == 0) {
-          // Reference LAST, update LAST.
-          // Set all buffer_idx to 0.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->refresh[0] = 1;
-        } else if (layer_id->spatial_layer_id == 1) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 1,
-          // GOLDEN (and all other refs) to slot 0.
-          // Update slot 1 (LAST).
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->ref_idx[0] = 1;
-          ref_frame_config->refresh[1] = 1;
-        } else if (layer_id->spatial_layer_id == 2) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 2,
-          // GOLDEN (and all other refs) to slot 1.
-          // Update slot 2 (LAST).
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 1;
-          ref_frame_config->ref_idx[0] = 2;
-          ref_frame_config->refresh[2] = 1;
+      if (simulcast_mode) {
+        ref_config_simulcast3SL3TL(ref_frame_config, layer_id, is_key_frame,
+                                   superframe_cnt_);
+      } else {
+        ref_config_3SL3TL(ref_frame_config, layer_id, is_key_frame,
+                          superframe_cnt_);
+        // Allow for top spatial layer to use additional temporal reference.
+        // Additional reference is only updated on base temporal layer, every
+        // 10 TL0 frames here.
+        if (multi_ref && layer_id->spatial_layer_id == 2) {
+          ref_frame_config->ref_idx[6] = 7;
+          if (!is_key_frame) ref_frame_config->reference[6] = 1;
+          if (base_count % 10 == 0 && layer_id->temporal_layer_id == 0)
+            ref_frame_config->refresh[7] = 1;
         }
-      } else if ((superframe_cnt_ - 1) % 4 == 0) {
-        // First top temporal enhancement layer.
-        layer_id->temporal_layer_id = 2;
-        if (layer_id->spatial_layer_id == 0) {
-          // Reference LAST (slot 0).
-          // Set GOLDEN to slot 3 and update slot 3.
-          // Set all other buffer_idx to slot 0.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->ref_idx[3] = 3;
-          ref_frame_config->refresh[3] = 1;
-        } else if (layer_id->spatial_layer_id == 1) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 1,
-          // GOLDEN (and all other refs) to slot 3.
-          // Set LAST2 to slot 4 and Update slot 4.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 3;
-          ref_frame_config->ref_idx[0] = 1;
-          ref_frame_config->ref_idx[1] = 4;
-          ref_frame_config->refresh[4] = 1;
-        } else if (layer_id->spatial_layer_id == 2) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 2,
-          // GOLDEN (and all other refs) to slot 4.
-          // No update.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 4;
-          ref_frame_config->ref_idx[0] = 2;
-        }
-      } else if ((superframe_cnt_ - 2) % 4 == 0) {
-        // Middle temporal enhancement layer.
-        layer_id->temporal_layer_id = 1;
-        if (layer_id->spatial_layer_id == 0) {
-          // Reference LAST.
-          // Set all buffer_idx to 0.
-          // Set GOLDEN to slot 3 and update slot 3.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->ref_idx[3] = 3;
-          ref_frame_config->refresh[3] = 1;
-        } else if (layer_id->spatial_layer_id == 1) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 1,
-          // GOLDEN (and all other refs) to slot 3.
-          // Set LAST2 to slot 4 and update slot 4.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 3;
-          ref_frame_config->ref_idx[0] = 1;
-          ref_frame_config->ref_idx[2] = 4;
-          ref_frame_config->refresh[4] = 1;
-        } else if (layer_id->spatial_layer_id == 2) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 2,
-          // GOLDEN (and all other refs) to slot 4.
-          // Set LAST2 to slot 5 and update slot 5.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 4;
-          ref_frame_config->ref_idx[0] = 2;
-          ref_frame_config->ref_idx[2] = 5;
-          ref_frame_config->refresh[5] = 1;
-        }
-      } else if ((superframe_cnt_ - 3) % 4 == 0) {
-        // Second top temporal enhancement layer.
-        layer_id->temporal_layer_id = 2;
-        if (layer_id->spatial_layer_id == 0) {
-          // Set LAST to slot 3 and reference LAST.
-          // Set GOLDEN to slot 3 and update slot 3.
-          // Set all other buffer_idx to 0.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->ref_idx[0] = 3;
-          ref_frame_config->ref_idx[3] = 3;
-          ref_frame_config->refresh[3] = 1;
-        } else if (layer_id->spatial_layer_id == 1) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 4,
-          // GOLDEN to slot 3. Set LAST2 to slot 4 and update slot 4.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->ref_idx[0] = 4;
-          ref_frame_config->ref_idx[3] = 3;
-          ref_frame_config->ref_idx[1] = 4;
-          ref_frame_config->refresh[4] = 1;
-        } else if (layer_id->spatial_layer_id == 2) {
-          // Reference LAST and GOLDEN. Set buffer_idx for LAST to slot 5,
-          // GOLDEN to slot 4. No update.
-          for (int i = 0; i < 7; i++) ref_frame_config->ref_idx[i] = 0;
-          ref_frame_config->ref_idx[0] = 5;
-          ref_frame_config->ref_idx[3] = 4;
-        }
-      }
-      if (layer_id->spatial_layer_id > 0) {
-        // Always reference GOLDEN (inter-layer prediction).
-        ref_frame_config->reference[3] = 1;
-        if (is_key_frame && layer_id->spatial_layer_id > 0) {
-          // On superframes whose base is key: remove LAST since GOLDEN
-          // is used as reference.
-          ref_frame_config->reference[0] = 0;
-        }
-      }
-      // Allow for top spatial layer to use additional temporal reference.
-      // Additional reference is only updated on base temporal layer, every
-      // 10 TL0 frames here.
-      if (multi_ref && layer_id->spatial_layer_id == 2) {
-        ref_frame_config->ref_idx[6] = 7;
-        if (!is_key_frame) ref_frame_config->reference[6] = 1;
-        if (base_count % 10 == 0 && layer_id->temporal_layer_id == 0)
-          ref_frame_config->refresh[7] = 1;
       }
     }
     // If the top spatial layer is first-time encoded in mid-sequence
@@ -1090,6 +1286,60 @@
     EXPECT_EQ((int)GetMismatchFrames(), 150);
   }
 
+  virtual void BasicRateTargetingSVC3TL3SLSimulcast() {
+    cfg_.rc_buf_initial_sz = 500;
+    cfg_.rc_buf_optimal_sz = 500;
+    cfg_.rc_buf_sz = 1000;
+    cfg_.rc_dropframe_thresh = 0;
+    cfg_.rc_min_quantizer = 0;
+    cfg_.rc_max_quantizer = 56;
+    cfg_.rc_end_usage = AOM_CBR;
+    cfg_.g_lag_in_frames = 0;
+    cfg_.g_error_resilient = 0;
+    cfg_.kf_max_dist = 150;
+    cfg_.kf_min_dist = 150;
+    int num_frames = 300;
+    ::libaom_test::I420VideoSource video("hantro_collage_w352h288.yuv", 352,
+                                         288, 30, 1, 0, num_frames);
+    const int bitrate_array[2] = { 500, 1000 };
+    cfg_.rc_target_bitrate = bitrate_array[GET_PARAM(4)];
+    ResetModel();
+    simulcast_mode_ = 1;
+    frame_to_start_decoding_ = cfg_.kf_max_dist;
+    layer_to_decode_ = 2;  // SL2
+    number_temporal_layers_ = 3;
+    number_spatial_layers_ = 3;
+    // SL0
+    const int bitrate_sl0 = 1 * cfg_.rc_target_bitrate / 8;
+    target_layer_bitrate_[0] = 50 * bitrate_sl0 / 100;
+    target_layer_bitrate_[1] = 70 * bitrate_sl0 / 100;
+    target_layer_bitrate_[2] = bitrate_sl0;
+    // SL1
+    const int bitrate_sl1 = 3 * cfg_.rc_target_bitrate / 8;
+    target_layer_bitrate_[3] = 50 * bitrate_sl1 / 100;
+    target_layer_bitrate_[4] = 70 * bitrate_sl1 / 100;
+    target_layer_bitrate_[5] = bitrate_sl1;
+    // SL2
+    const int bitrate_sl2 = 4 * cfg_.rc_target_bitrate / 8;
+    target_layer_bitrate_[6] = 50 * bitrate_sl2 / 100;
+    target_layer_bitrate_[7] = 70 * bitrate_sl2 / 100;
+    target_layer_bitrate_[8] = bitrate_sl2;
+    ASSERT_NO_FATAL_FAILURE(RunLoop(&video));
+    // Only SL2 layer is decoded.
+    for (int tl = 0; tl < number_temporal_layers_; tl++) {
+      int i = layer_to_decode_ * number_temporal_layers_ + tl;
+      ASSERT_GE(effective_datarate_tl[i], target_layer_bitrate_[i] * 0.6)
+          << " The datarate for the file is lower than target by too much!";
+      ASSERT_LE(effective_datarate_tl[i], target_layer_bitrate_[i] * 1.7)
+          << " The datarate for the file is greater than target by too much!";
+    }
+    // Only top spatial layer (SL2) is decoded, starting at frame 150
+    // (frame_to_start_decoding_), so there (300 - 150) / 2 = 75
+    // non-reference frames, so mismatch is 75.
+    int num_mismatch = (num_frames - frame_to_start_decoding_) / 2;
+    EXPECT_EQ((int)GetMismatchFrames(), num_mismatch);
+  }
+
   virtual void BasicRateTargetingSVC1TL2SLIntraOnlyTest() {
     cfg_.rc_buf_initial_sz = 500;
     cfg_.rc_buf_optimal_sz = 500;
@@ -2133,6 +2383,7 @@
   int screen_mode_;
   int rps_mode_;
   int rps_recovery_frame_;
+  int simulcast_mode_;
 
   int user_define_frame_qp_;
   int frame_qp_;
@@ -2199,6 +2450,14 @@
   BasicRateTargetingSVC3TL3SLIntraMidSeqDecodeAll();
 }
 
+// Check simulcast mode for 3 spatial layers, 3 temporal,
+// Key frame is inserted on base SLO in mid-stream, and verify that the
+// top spatial layer (SL2) case be decoded, starting with an Intra-only frame.
+// Verify that we can decode all frames for SL2 with no mismatch.
+TEST_P(DatarateTestSVC, BasicRateTargetingSVC3TL3SLSimulcast) {
+  BasicRateTargetingSVC3TL3SLSimulcast();
+}
+
 // Check basic rate targeting for CBR, for 2 spatial layers, 1 temporal,
 // with Intra-only frame inserted in the stream.
 TEST_P(DatarateTestSVC, BasicRateTargetingSVC1TL2SLIntraOnly) {