shithub: libvpx

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Updates to skin detection

-Use 8x8 or 16x16 blocks.
-Option to use average of center pixel(s).

Change-Id: I7d962da30039d41385843e11606bc6482c7906f9

--- a/vp9/encoder/vp9_skin_detection.c

+++ b/vp9/encoder/vp9_skin_detection.c

@@ -51,7 +51,7 @@

 #ifdef OUTPUT_YUV_SKINMAP

 // For viewing skin map on input source.

 void vp9_compute_skin_map(VP9_COMP *const cpi, FILE *yuv_skinmap_file) {

-  int i, j, mi_row, mi_col;

+  int i, j, mi_row, mi_col, num_bl;

   VP9_COMMON *const cm = &cpi->common;

   uint8_t *y;

   const uint8_t *src_y = cpi->Source->y_buffer;

@@ -59,6 +59,15 @@

   const uint8_t *src_v = cpi->Source->v_buffer;

   const int src_ystride = cpi->Source->y_stride;

   const int src_uvstride = cpi->Source->uv_stride;

+  int y_bsize = 16;  // Use 8x8 or 16x16.

+  int uv_bsize = y_bsize >> 1;

+  int ypos = y_bsize >> 1;

+  int uvpos = uv_bsize >> 1;

+  int shy = (y_bsize == 8) ? 3 : 4;

+  int shuv = shy - 1;

+  int fac = y_bsize / 8;

+  // Use center pixel or average of center 2x2 pixels.

+  int mode_filter = 1;

   YV12_BUFFER_CONFIG skinmap;

   memset(&skinmap, 0, sizeof(YV12_BUFFER_CONFIG));

   if (vpx_alloc_frame_buffer(&skinmap, cm->width, cm->height,

@@ -69,19 +78,34 @@

   }

   memset(skinmap.buffer_alloc, 128, skinmap.frame_size);

   y = skinmap.y_buffer;

-  // Loop through 8x8 blocks and set skin map based on center pixel of block.

+  // Loop through blocks and set skin map based on center pixel of block.

   // Set y to white for skin block, otherwise set to source with gray scale.

   // Ignore rightmost/bottom boundary blocks.

-  for (mi_row = 0; mi_row < cm->mi_rows - 1; ++mi_row) {

-    for (mi_col = 0; mi_col < cm->mi_cols - 1; ++mi_col) {

-      // Use middle pixel for each 8x8 block for skin detection.

-      // If middle pixel is skin, assign whole 8x8 block to skin.

-      const uint8_t ysource = src_y[4 * src_ystride + 4];

-      const uint8_t usource = src_u[2 * src_uvstride + 2];

-      const uint8_t vsource = src_v[2 * src_uvstride + 2];

+  for (mi_row = 0; mi_row < cm->mi_rows - 1; mi_row += fac) {

+    num_bl = 0;

+    for (mi_col = 0; mi_col < cm->mi_cols - 1; mi_col += fac) {

+      // Select pixel for each block for skin detection.

+      // Use center pixel, or 2x2 average at center.

+      uint8_t ysource = src_y[ypos * src_ystride + ypos];

+      uint8_t usource = src_u[uvpos * src_uvstride + uvpos];

+      uint8_t vsource = src_v[uvpos * src_uvstride + uvpos];

+      uint8_t ysource2 = src_y[(ypos + 1) * src_ystride + ypos];

+      uint8_t usource2 = src_u[(uvpos + 1) * src_uvstride + uvpos];

+      uint8_t vsource2 = src_v[(uvpos + 1) * src_uvstride + uvpos];

+      uint8_t ysource3 = src_y[ypos * src_ystride + (ypos + 1)];

+      uint8_t usource3 = src_u[uvpos * src_uvstride + (uvpos  + 1)];

+      uint8_t vsource3 = src_v[uvpos * src_uvstride + (uvpos +  1)];

+      uint8_t ysource4 = src_y[(ypos + 1) * src_ystride + (ypos + 1)];

+      uint8_t usource4 = src_u[(uvpos + 1) * src_uvstride + (uvpos  + 1)];

+      uint8_t vsource4 = src_v[(uvpos + 1) * src_uvstride + (uvpos +  1)];

+      if (mode_filter == 1) {

+        ysource = (ysource + ysource2 + ysource3 + ysource4) >> 2;

+        usource = (usource + usource2 + usource3 + usource4) >> 2;

+        vsource = (vsource + vsource2 + vsource3 + vsource4) >> 2;

+      }

       const int is_skin = vp9_skin_pixel(ysource, usource, vsource);

-      for (i = 0; i < 8; i++) {

-        for (j = 0; j < 8; j++) {

+      for (i = 0; i < y_bsize; i++) {

+        for (j = 0; j < y_bsize; j++) {

           if (is_skin)

             y[i * src_ystride + j] = 255;

           else

@@ -88,15 +112,16 @@

             y[i * src_ystride + j] = src_y[i * src_ystride + j];

         }

       }

-      y += 8;

-      src_y += 8;

-      src_u += 4;

-      src_v += 4;

+      num_bl++;

+      y += y_bsize;

+      src_y += y_bsize;

+      src_u += uv_bsize;

+      src_v += uv_bsize;

     }

-    y += (src_ystride << 3) - ((cm->mi_cols - 1) << 3);

-    src_y += (src_ystride << 3) - ((cm->mi_cols - 1) << 3);

-    src_u += (src_uvstride << 2) - ((cm->mi_cols - 1) << 2);

-    src_v += (src_uvstride << 2) - ((cm->mi_cols - 1) << 2);

+    y += (src_ystride << shy) - (num_bl << shy);

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

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

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

   }

   vp9_write_yuv_frame_420(&skinmap, yuv_skinmap_file);

   vpx_free_frame_buffer(&skinmap);