Make last frame source available in current frame encoding

While encoding a frame, its last frame source can be used to give
acurate motion information. This patch prevents last frame to be
overwritten so that it is available during current frame encoding.

The last source is scaled when it is necessary. cpi->Last_Source
points to the last source frame.

Change-Id: I0e1ef5e9e1d2badf9d0c7a1a44a7ed5b24c09425

4 files changed, 83 insertions, 18 deletions

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 122477906..65f92d087 100644
--- a/vp9/encoder/vp9_onyx_if.c
+++ b/vp9/encoder/vp9_onyx_if.c
@@ -200,6 +200,7 @@ 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);
 
@@ -960,6 +961,13 @@ 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);
 
   {
@@ -1001,6 +1009,13 @@ 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;
 
@@ -2914,6 +2929,19 @@ 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();
@@ -3332,6 +3360,7 @@ 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);
 
@@ -3394,6 +3423,13 @@ 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;
@@ -3432,6 +3468,13 @@ 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 582fa0ea3..8255073c9 100644
--- a/vp9/encoder/vp9_onyx_int.h
+++ b/vp9/encoder/vp9_onyx_int.h
@@ -596,10 +596,14 @@ 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;