diff --git a/vp9/encoder/vp9_lookahead.c b/vp9/encoder/vp9_lookahead.c
index a88d5ecf8..cf03e0142 100644
--- a/vp9/encoder/vp9_lookahead.c
+++ b/vp9/encoder/vp9_lookahead.c
@@ -28,8 +28,8 @@ struct lookahead_ctx {
 
 
 /* Return the buffer at the given absolute index and increment the index */
-static struct lookahead_entry * pop(struct lookahead_ctx *ctx,
-                                    unsigned int *idx) {
+static struct lookahead_entry *pop(struct lookahead_ctx *ctx,
+                                   unsigned int *idx) {
   unsigned int index = *idx;
   struct lookahead_entry *buf = ctx->buf + index;
 
@@ -55,16 +55,19 @@ void vp9_lookahead_destroy(struct lookahead_ctx *ctx) {
 }
 
 
-struct lookahead_ctx * vp9_lookahead_init(unsigned int width,
-                                          unsigned int height,
-                                          unsigned int subsampling_x,
-                                          unsigned int subsampling_y,
-                                          unsigned int depth) {
+struct lookahead_ctx *vp9_lookahead_init(unsigned int width,
+                                         unsigned int height,
+                                         unsigned int subsampling_x,
+                                         unsigned int subsampling_y,
+                                         unsigned int depth) {
   struct lookahead_ctx *ctx = NULL;
 
   // Clamp the lookahead queue depth
   depth = clamp(depth, 1, MAX_LAG_BUFFERS);
 
+  // Allocate memory to keep previous source frames available.
+  depth += MAX_PRE_FRAMES;
+
   // Allocate the lookahead structures
   ctx = calloc(1, sizeof(*ctx));
   if (ctx) {
@@ -96,7 +99,7 @@ int vp9_lookahead_push(struct lookahead_ctx *ctx, YV12_BUFFER_CONFIG   *src,
   int mb_cols = (src->y_width + 15) >> 4;
 #endif
 
-  if (ctx->sz + 1 > ctx->max_sz)
+  if (ctx->sz + 1  + MAX_PRE_FRAMES > ctx->max_sz)
     return 1;
   ctx->sz++;
   buf = pop(ctx, &ctx->write_idx);
@@ -159,11 +162,11 @@ int vp9_lookahead_push(struct lookahead_ctx *ctx, YV12_BUFFER_CONFIG   *src,
 }
 
 
-struct lookahead_entry * vp9_lookahead_pop(struct lookahead_ctx *ctx,
-                                           int drain) {
+struct lookahead_entry *vp9_lookahead_pop(struct lookahead_ctx *ctx,
+                                          int drain) {
   struct lookahead_entry *buf = NULL;
 
-  if (ctx->sz && (drain || ctx->sz == ctx->max_sz)) {
+  if (ctx->sz && (drain || ctx->sz == ctx->max_sz - MAX_PRE_FRAMES)) {
     buf = pop(ctx, &ctx->read_idx);
     ctx->sz--;
   }
@@ -171,16 +174,28 @@ struct lookahead_entry * vp9_lookahead_pop(struct lookahead_ctx *ctx,
 }
 
 
-struct lookahead_entry * vp9_lookahead_peek(struct lookahead_ctx *ctx,
-                                            int index) {
+struct lookahead_entry *vp9_lookahead_peek(struct lookahead_ctx *ctx,
+                                           int index) {
   struct lookahead_entry *buf = NULL;
 
-  if (index < (int)ctx->sz) {
-    index += ctx->read_idx;
-    if (index >= (int)ctx->max_sz)
-      index -= ctx->max_sz;
-    buf = ctx->buf + index;
+  if (index >= 0) {
+    // Forward peek
+    if (index < (int)ctx->sz) {
+      index += ctx->read_idx;
+      if (index >= (int)ctx->max_sz)
+        index -= ctx->max_sz;
+      buf = ctx->buf + index;
+    }
+  } else if (index < 0) {
+    // Backward peek
+    if (-index <= MAX_PRE_FRAMES) {
+      index += ctx->read_idx;
+      if (index < 0)
+        index += ctx->max_sz;
+      buf = ctx->buf + index;
+    }
   }
+
   return buf;
 }
 
diff --git a/vp9/encoder/vp9_lookahead.h b/vp9/encoder/vp9_lookahead.h
index ff63c0d0d..046c533cc 100644
--- a/vp9/encoder/vp9_lookahead.h
+++ b/vp9/encoder/vp9_lookahead.h
@@ -20,6 +20,9 @@ extern "C" {
 
 #define MAX_LAG_BUFFERS 25
 
+// The max of past frames we want to keep in the queue.
+#define MAX_PRE_FRAMES 1
+
 struct lookahead_entry {
   YV12_BUFFER_CONFIG  img;
   int64_t             ts_start;
diff --git a/vp9/encoder/vp9_onyx_if.c b/vp9/encoder/vp9_onyx_if.c
index f112fa24f..f425a16a2 100644
--- a/vp9/encoder/vp9_onyx_if.c
+++ b/vp9/encoder/vp9_onyx_if.c
@@ -189,6 +189,7 @@ static void dealloc_compressor_data(VP9_COMP *cpi) {
 
   vp9_free_frame_buffer(&cpi->last_frame_uf);
   vp9_free_frame_buffer(&cpi->scaled_source);
+  vp9_free_frame_buffer(&cpi->scaled_last_source);
   vp9_free_frame_buffer(&cpi->alt_ref_buffer);
   vp9_lookahead_destroy(cpi->lookahead);
 
@@ -595,6 +596,13 @@ void vp9_alloc_compressor_data(VP9_COMP *cpi) {
     vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
                        "Failed to allocate scaled source buffer");
 
+  if (vp9_alloc_frame_buffer(&cpi->scaled_last_source,
+                             cm->width, cm->height,
+                             cm->subsampling_x, cm->subsampling_y,
+                             VP9_ENC_BORDER_IN_PIXELS))
+    vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
+                       "Failed to allocate scaled last source buffer");
+
   vpx_free(cpi->tok);
 
   {
@@ -636,6 +644,13 @@ static void update_frame_size(VP9_COMP *cpi) {
     vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
                        "Failed to reallocate scaled source buffer");
 
+  if (vp9_realloc_frame_buffer(&cpi->scaled_last_source,
+                               cm->width, cm->height,
+                               cm->subsampling_x, cm->subsampling_y,
+                               VP9_ENC_BORDER_IN_PIXELS, NULL, NULL, NULL))
+    vpx_internal_error(&cm->error, VPX_CODEC_MEM_ERROR,
+                       "Failed to reallocate scaled last source buffer");
+
   {
     int y_stride = cpi->scaled_source.y_stride;
 
@@ -2554,6 +2569,19 @@ static void encode_frame_to_data_rate(VP9_COMP *cpi,
   } else {
     cpi->Source = cpi->un_scaled_source;
   }
+
+  // Scale the last source buffer, if required.
+  if (cpi->unscaled_last_source != NULL) {
+    if (cm->mi_cols * MI_SIZE != cpi->unscaled_last_source->y_width ||
+        cm->mi_rows * MI_SIZE != cpi->unscaled_last_source->y_height) {
+      scale_and_extend_frame_nonnormative(cpi->unscaled_last_source,
+                                          &cpi->scaled_last_source);
+      cpi->Last_Source = &cpi->scaled_last_source;
+    } else {
+      cpi->Last_Source = cpi->unscaled_last_source;
+    }
+  }
+
   vp9_scale_references(cpi);
 
   vp9_clear_system_state();
@@ -2985,6 +3013,7 @@ int vp9_get_compressed_data(VP9_COMP *cpi, unsigned int *frame_flags,
   vpx_usec_timer_start(&cmptimer);
 
   cpi->source = NULL;
+  cpi->last_source = NULL;
 
   set_high_precision_mv(cpi, ALTREF_HIGH_PRECISION_MV);
 
@@ -3047,6 +3076,13 @@ int vp9_get_compressed_data(VP9_COMP *cpi, unsigned int *frame_flags,
 #if CONFIG_MULTIPLE_ARF
     int i;
 #endif
+
+    // Get last frame source.
+    if (cm->current_video_frame > 0) {
+      if ((cpi->last_source = vp9_lookahead_peek(cpi->lookahead, -1)) == NULL)
+        return -1;
+    }
+
     if ((cpi->source = vp9_lookahead_pop(cpi->lookahead, flush))) {
       cm->show_frame = 1;
       cm->intra_only = 0;
@@ -3085,6 +3121,13 @@ int vp9_get_compressed_data(VP9_COMP *cpi, unsigned int *frame_flags,
   if (cpi->source) {
     cpi->un_scaled_source = cpi->Source = force_src_buffer ? force_src_buffer
                                                            : &cpi->source->img;
+
+  if (cpi->last_source != NULL) {
+    cpi->unscaled_last_source = &cpi->last_source->img;
+  } else {
+    cpi->unscaled_last_source = NULL;
+  }
+
     *time_stamp = cpi->source->ts_start;
     *time_end = cpi->source->ts_end;
     *frame_flags = cpi->source->flags;
diff --git a/vp9/encoder/vp9_onyx_int.h b/vp9/encoder/vp9_onyx_int.h
index 6dbe4d474..1ee5cc5d7 100644
--- a/vp9/encoder/vp9_onyx_int.h
+++ b/vp9/encoder/vp9_onyx_int.h
@@ -307,10 +307,14 @@ typedef struct VP9_COMP {
 #else
   struct lookahead_entry  *alt_ref_source;
 #endif
+  struct lookahead_entry  *last_source;
 
   YV12_BUFFER_CONFIG *Source;
+  YV12_BUFFER_CONFIG *Last_Source;  // NULL for first frame and alt_ref frames
   YV12_BUFFER_CONFIG *un_scaled_source;
   YV12_BUFFER_CONFIG scaled_source;
+  YV12_BUFFER_CONFIG *unscaled_last_source;
+  YV12_BUFFER_CONFIG scaled_last_source;
 
   int key_frame_frequency;