shithub: libvpx

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vp8: Remove isolated skin & non skin blocks.

Neutral on RTC metrics and speed on Pixel.

Change-Id: I26b907483fe133e6e4c1009d147631f0d0e0f2fb

--- a/vp8/encoder/onyx_if.c

+++ b/vp8/encoder/onyx_if.c

@@ -628,16 +628,15 @@

   const SKIN_DETECTION_BLOCK_SIZE bsize =

       (cm->Width * cm->Height <= 352 * 288) ? SKIN_8X8 : SKIN_16X16;

-  int offset = 0;

+

   for (mb_row = 0; mb_row < cm->mb_rows; mb_row++) {

     num_bl = 0;

     for (mb_col = 0; mb_col < cm->mb_cols; mb_col++) {

       const int bl_index = mb_row * cm->mb_cols + mb_col;

-      cpi->skin_map[offset] =

+      cpi->skin_map[bl_index] =

           vp8_compute_skin_block(src_y, src_u, src_v, src_ystride, src_uvstride,

                                  bsize, cpi->consec_zero_last[bl_index], 0);

       num_bl++;

-      offset++;

       src_y += 16;

       src_u += 8;

       src_v += 8;

@@ -645,6 +644,29 @@

     src_y += (src_ystride << 4) - (num_bl << 4);

     src_u += (src_uvstride << 3) - (num_bl << 3);

     src_v += (src_uvstride << 3) - (num_bl << 3);

+  }

+

+  // Remove isolated skin blocks (none of its neighbors are skin) and isolated

+  // non-skin blocks (all of its neighbors are skin). Skip the boundary.

+  for (mb_row = 1; mb_row < cm->mb_rows - 1; mb_row++) {

+    for (mb_col = 1; mb_col < cm->mb_cols - 1; mb_col++) {

+      const int bl_index = mb_row * cm->mb_cols + mb_col;

+      int num_neighbor = 0;

+      int mi, mj;

+      int non_skin_threshold = 8;

+

+      for (mi = -1; mi <= 1; mi += 1) {

+        for (mj = -1; mj <= 1; mj += 1) {

+          int bl_neighbor_index = (mb_row + mi) * cm->mb_cols + mb_col + mj;

+          if (cpi->skin_map[bl_neighbor_index]) num_neighbor++;

+        }

+      }

+

+      if (cpi->skin_map[bl_index] && num_neighbor < 2)

+        cpi->skin_map[bl_index] = 0;

+      if (!cpi->skin_map[bl_index] && num_neighbor == non_skin_threshold)

+        cpi->skin_map[bl_index] = 1;

+    }

   }

 }