shithub: libvpx

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Non-rd partition: Use force split on 16x16 for low resolutions.

For low resolutions, whem 4x4downsample is used for variance,
use the same force split (that is used for 8x8downsample) for 16x16 blocks.

No change in metrics. Small improvement visually.

Change-Id: I915b9895902d0b9a41e75d37fee1bf3714d2366d

--- a/vp9/encoder/vp9_encodeframe.c

+++ b/vp9/encoder/vp9_encodeframe.c

@@ -401,7 +401,6 @@

   variance_node vt;

   const int block_width = num_8x8_blocks_wide_lookup[bsize];

   const int block_height = num_8x8_blocks_high_lookup[bsize];

-  const int low_res = (cm->width <= 352 && cm->height <= 288);

   assert(block_height == block_width);

   tree_to_node(data, bsize, &vt);

@@ -414,7 +413,7 @@

   // No check for vert/horiz split as too few samples for variance.

   if (bsize == bsize_min) {

     // Variance already computed to set the force_split.

-    if (low_res || cm->frame_type == KEY_FRAME)

+    if (cm->frame_type == KEY_FRAME)

       get_variance(&vt.part_variances->none);

     if (mi_col + block_width / 2 < cm->mi_cols &&

         mi_row + block_height / 2 < cm->mi_rows &&

@@ -425,7 +424,7 @@

     return 0;

   } else if (bsize > bsize_min) {

     // Variance already computed to set the force_split.

-    if (low_res || cm->frame_type == KEY_FRAME)

+    if (cm->frame_type == KEY_FRAME)

       get_variance(&vt.part_variances->none);

     // For key frame: take split for bsize above 32X32 or very high variance.

     if (cm->frame_type == KEY_FRAME &&

@@ -897,6 +896,14 @@

         for (m = 0; m < 4; m++)

           fill_variance_tree(&vtemp->split[m], BLOCK_8X8);

         fill_variance_tree(vtemp, BLOCK_16X16);

+        // If variance of this 16x16 block is above the threshold, force block

+        // to split. This also forces a split on the upper levels.

+        get_variance(&vtemp->part_variances.none);

+        if (vtemp->part_variances.none.variance > thresholds[2]) {

+          force_split[5 + i2 + j] = 1;

+          force_split[i + 1] = 1;

+          force_split[0] = 1;

+        }

       }

     }

     fill_variance_tree(&vt.split[i], BLOCK_32X32);