shithub: libvpx

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ref: 327c9bb1da0e0ceac4293ab42fa8c25e8f1706c9
parent: de1a9c77a7e54f6c0dce272850c43251f38b6c6c
author: Jerome Jiang <jianj@google.com>
date: Thu May 25 09:58:20 EDT 2017

Refactor: Move vp8 skin detection to new files.

Change-Id: If760f28cbbf22beac1cc9bd1546f13831e9dd3f0

--- /dev/null
+++ b/vp8/common/skin_detection.c
@@ -1,0 +1,104 @@
+/*
+ *  Copyright (c) 2015 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#include "vp8/common/skin_detection.h"
+
+#define MODEL_MODE 1
+
+// Fixed-point skin color model parameters.
+static const int skin_mean[5][2] = { { 7463, 9614 },
+                                     { 6400, 10240 },
+                                     { 7040, 10240 },
+                                     { 8320, 9280 },
+                                     { 6800, 9614 } };
+static const int skin_inv_cov[4] = { 4107, 1663, 1663, 2157 };  // q16
+static const int skin_threshold[6] = { 1570636, 1400000, 800000,
+                                       800000,  800000,  800000 };  // q18
+
+// Thresholds on luminance.
+static const int y_low = 40;
+static const int y_high = 220;
+
+// Evaluates the Mahalanobis distance measure for the input CbCr values.
+static int evaluate_skin_color_difference(int cb, int cr, int idx) {
+  const int cb_q6 = cb << 6;
+  const int cr_q6 = cr << 6;
+  const int cb_diff_q12 =
+      (cb_q6 - skin_mean[idx][0]) * (cb_q6 - skin_mean[idx][0]);
+  const int cbcr_diff_q12 =
+      (cb_q6 - skin_mean[idx][0]) * (cr_q6 - skin_mean[idx][1]);
+  const int cr_diff_q12 =
+      (cr_q6 - skin_mean[idx][1]) * (cr_q6 - skin_mean[idx][1]);
+  const int cb_diff_q2 = (cb_diff_q12 + (1 << 9)) >> 10;
+  const int cbcr_diff_q2 = (cbcr_diff_q12 + (1 << 9)) >> 10;
+  const int cr_diff_q2 = (cr_diff_q12 + (1 << 9)) >> 10;
+  const int skin_diff =
+      skin_inv_cov[0] * cb_diff_q2 + skin_inv_cov[1] * cbcr_diff_q2 +
+      skin_inv_cov[2] * cbcr_diff_q2 + skin_inv_cov[3] * cr_diff_q2;
+  return skin_diff;
+}
+
+// Checks if the input yCbCr values corresponds to skin color.
+int skin_pixel(int y, int cb, int cr, int motion) {
+  if (y < y_low || y > y_high) {
+    return 0;
+  } else {
+    if (MODEL_MODE == 0) {
+      return (evaluate_skin_color_difference(cb, cr, 0) < skin_threshold[0]);
+    } else {
+      int i = 0;
+      // Exit on grey.
+      if (cb == 128 && cr == 128) return 0;
+      // Exit on very strong cb.
+      if (cb > 150 && cr < 110) return 0;
+      for (; i < 5; ++i) {
+        int skin_color_diff = evaluate_skin_color_difference(cb, cr, i);
+        if (skin_color_diff < skin_threshold[i + 1]) {
+          if (y < 60 && skin_color_diff > 3 * (skin_threshold[i + 1] >> 2)) {
+            return 0;
+          } else if (motion == 0 &&
+                     skin_color_diff > (skin_threshold[i + 1] >> 1)) {
+            return 0;
+          } else {
+            return 1;
+          }
+        }
+        // Exit if difference is much large than the threshold.
+        if (skin_color_diff > (skin_threshold[i + 1] << 3)) {
+          return 0;
+        }
+      }
+      return 0;
+    }
+  }
+}
+
+int compute_skin_block(const uint8_t *y, const uint8_t *u, const uint8_t *v,
+                       int stride, int strideuv, int consec_zeromv,
+                       int curr_motion_magn) {
+  // No skin if block has been zero/small motion for long consecutive time.
+  if (consec_zeromv > 60 && curr_motion_magn == 0) {
+    return 0;
+  } else {
+    int motion = 1;
+    // Take center pixel in block to determine is_skin.
+    const int ysource = (y[7 * stride + 7] + y[7 * stride + 8] +
+                         y[8 * stride + 7] + y[8 * stride + 8]) >>
+                        2;
+    const int usource = (u[3 * strideuv + 3] + u[3 * strideuv + 4] +
+                         u[4 * strideuv + 3] + u[4 * strideuv + 4]) >>
+                        2;
+    const int vsource = (v[3 * strideuv + 3] + v[3 * strideuv + 4] +
+                         v[4 * strideuv + 3] + v[4 * strideuv + 4]) >>
+                        2;
+    if (consec_zeromv > 25 && curr_motion_magn == 0) motion = 0;
+    return skin_pixel(ysource, usource, vsource, motion);
+  }
+}
--- /dev/null
+++ b/vp8/common/skin_detection.h
@@ -1,0 +1,30 @@
+/*
+ *  Copyright (c) 2015 The WebM project authors. All Rights Reserved.
+ *
+ *  Use of this source code is governed by a BSD-style license
+ *  that can be found in the LICENSE file in the root of the source
+ *  tree. An additional intellectual property rights grant can be found
+ *  in the file PATENTS.  All contributing project authors may
+ *  be found in the AUTHORS file in the root of the source tree.
+ */
+
+#ifndef VP8_ENCODER_SKIN_DETECTION_H_
+#define VP8_ENCODER_SKIN_DETECTION_H_
+
+#include "vpx/vpx_integer.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+int skin_pixel(int y, int cb, int cr, int motion);
+
+int compute_skin_block(const uint8_t *y, const uint8_t *u, const uint8_t *v,
+                       int stride, int strideuv, int consec_zeromv,
+                       int curr_motion_magn);
+
+#ifdef __cplusplus
+}  // extern "C"
+#endif
+
+#endif  // VP8_ENCODER_SKIN_DETECTION_H_
--- a/vp8/encoder/pickinter.c
+++ b/vp8/encoder/pickinter.c
@@ -25,6 +25,7 @@
 #include "vp8/common/reconintra4x4.h"
 #include "vpx_dsp/variance.h"
 #include "mcomp.h"
+#include "vp8/common/skin_detection.h"
 #include "rdopt.h"
 #include "vpx_dsp/vpx_dsp_common.h"
 #include "vpx_mem/vpx_mem.h"
@@ -36,82 +37,9 @@
 extern unsigned int cnt_pm;
 #endif
 
-#define MODEL_MODE 1
-
 extern const int vp8_ref_frame_order[MAX_MODES];
 extern const MB_PREDICTION_MODE vp8_mode_order[MAX_MODES];
 
-// Fixed point implementation of a skin color classifier. Skin color
-// is model by a Gaussian distribution in the CbCr color space.
-// See ../../test/skin_color_detector_test.cc where the reference
-// skin color classifier is defined.
-
-// Fixed-point skin color model parameters.
-static const int skin_mean[5][2] = { { 7463, 9614 },
-                                     { 6400, 10240 },
-                                     { 7040, 10240 },
-                                     { 8320, 9280 },
-                                     { 6800, 9614 } };
-static const int skin_inv_cov[4] = { 4107, 1663, 1663, 2157 };  // q16
-static const int skin_threshold[6] = { 1570636, 1400000, 800000,
-                                       800000,  800000,  800000 };  // q18
-
-// Evaluates the Mahalanobis distance measure for the input CbCr values.
-static int evaluate_skin_color_difference(int cb, int cr, int idx) {
-  const int cb_q6 = cb << 6;
-  const int cr_q6 = cr << 6;
-  const int cb_diff_q12 =
-      (cb_q6 - skin_mean[idx][0]) * (cb_q6 - skin_mean[idx][0]);
-  const int cbcr_diff_q12 =
-      (cb_q6 - skin_mean[idx][0]) * (cr_q6 - skin_mean[idx][1]);
-  const int cr_diff_q12 =
-      (cr_q6 - skin_mean[idx][1]) * (cr_q6 - skin_mean[idx][1]);
-  const int cb_diff_q2 = (cb_diff_q12 + (1 << 9)) >> 10;
-  const int cbcr_diff_q2 = (cbcr_diff_q12 + (1 << 9)) >> 10;
-  const int cr_diff_q2 = (cr_diff_q12 + (1 << 9)) >> 10;
-  const int skin_diff =
-      skin_inv_cov[0] * cb_diff_q2 + skin_inv_cov[1] * cbcr_diff_q2 +
-      skin_inv_cov[2] * cbcr_diff_q2 + skin_inv_cov[3] * cr_diff_q2;
-  return skin_diff;
-}
-
-// Checks if the input yCbCr values corresponds to skin color.
-static int is_skin_color(int y, int cb, int cr, int consec_zeromv) {
-  if (y < 40 || y > 220) {
-    return 0;
-  } else {
-    if (MODEL_MODE == 0) {
-      return (evaluate_skin_color_difference(cb, cr, 0) < skin_threshold[0]);
-    } else {
-      int i = 0;
-      // No skin if block has been zero motion for long consecutive time.
-      if (consec_zeromv > 60) return 0;
-      // Exit on grey.
-      if (cb == 128 && cr == 128) return 0;
-      // Exit on very strong cb.
-      if (cb > 150 && cr < 110) return 0;
-      for (; i < 5; ++i) {
-        int skin_color_diff = evaluate_skin_color_difference(cb, cr, i);
-        if (skin_color_diff < skin_threshold[i + 1]) {
-          if (y < 60 && skin_color_diff > 3 * (skin_threshold[i + 1] >> 2)) {
-            return 0;
-          } else if (consec_zeromv > 25 &&
-                     skin_color_diff > (skin_threshold[i + 1] >> 1)) {
-            return 0;
-          } else {
-            return 1;
-          }
-        }
-        // Exit if difference is much large than the threshold.
-        if (skin_color_diff > (skin_threshold[i + 1] << 3)) {
-          return 0;
-        }
-      }
-      return 0;
-    }
-  }
-}
-
 static int macroblock_corner_grad(unsigned char *signal, int stride,
                                   int offsetx, int offsety, int sgnx,
                                   int sgny) {
@@ -760,27 +688,12 @@
 #endif
 
   // Check if current macroblock is in skin area.
-  {
-    const int y = (x->src.y_buffer[7 * x->src.y_stride + 7] +
-                   x->src.y_buffer[7 * x->src.y_stride + 8] +
-                   x->src.y_buffer[8 * x->src.y_stride + 7] +
-                   x->src.y_buffer[8 * x->src.y_stride + 8]) >>
-                  2;
-    const int cb = (x->src.u_buffer[3 * x->src.uv_stride + 3] +
-                    x->src.u_buffer[3 * x->src.uv_stride + 4] +
-                    x->src.u_buffer[4 * x->src.uv_stride + 3] +
-                    x->src.u_buffer[4 * x->src.uv_stride + 4]) >>
-                   2;
-    const int cr = (x->src.v_buffer[3 * x->src.uv_stride + 3] +
-                    x->src.v_buffer[3 * x->src.uv_stride + 4] +
-                    x->src.v_buffer[4 * x->src.uv_stride + 3] +
-                    x->src.v_buffer[4 * x->src.uv_stride + 4]) >>
-                   2;
-    x->is_skin = 0;
-    if (!cpi->oxcf.screen_content_mode) {
-      int block_index = mb_row * cpi->common.mb_cols + mb_col;
-      x->is_skin = is_skin_color(y, cb, cr, cpi->consec_zero_last[block_index]);
-    }
+  x->is_skin = 0;
+  if (!cpi->oxcf.screen_content_mode) {
+    int block_index = mb_row * cpi->common.mb_cols + mb_col;
+    x->is_skin = compute_skin_block(
+        x->src.y_buffer, x->src.u_buffer, x->src.v_buffer, x->src.y_stride,
+        x->src.uv_stride, cpi->consec_zero_last[block_index], 0);
   }
 #if CONFIG_TEMPORAL_DENOISING
   if (cpi->oxcf.noise_sensitivity) {
--- a/vp8/vp8cx.mk
+++ b/vp8/vp8cx.mk
@@ -61,6 +61,8 @@
 VP8_CX_SRCS-yes += encoder/rdopt.c
 VP8_CX_SRCS-yes += encoder/segmentation.c
 VP8_CX_SRCS-yes += encoder/segmentation.h
+VP8_CX_SRCS-yes += common/skin_detection.c
+VP8_CX_SRCS-yes += common/skin_detection.h
 VP8_CX_SRCS-yes += encoder/tokenize.c
 VP8_CX_SRCS-yes += encoder/dct_value_cost.h
 VP8_CX_SRCS-yes += encoder/dct_value_tokens.h