ref: d545c19afaa08138702f023e736e6c0da5107c99
dir: /vp9/encoder/vp9_skin_detection.c/
/* * 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 <limits.h> #include <math.h> #include "vp9/common/vp9_blockd.h" #include "vp9/encoder/vp9_encoder.h" #include "vp9/encoder/vp9_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; } int vp9_skin_pixel(const uint8_t y, const uint8_t cb, const uint8_t 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 vp9_compute_skin_block(const uint8_t *y, const uint8_t *u, const uint8_t *v, int stride, int strideuv, int bsize, 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 y_width_shift = (4 << b_width_log2_lookup[bsize]) >> 1; const int y_height_shift = (4 << b_height_log2_lookup[bsize]) >> 1; const int uv_width_shift = y_width_shift >> 1; const int uv_height_shift = y_height_shift >> 1; const uint8_t ysource = y[y_height_shift * stride + y_width_shift]; const uint8_t usource = u[uv_height_shift * strideuv + uv_width_shift]; const uint8_t vsource = v[uv_height_shift * strideuv + uv_width_shift]; if (consec_zeromv > 25 && curr_motion_magn == 0) motion = 0; return vp9_skin_pixel(ysource, usource, vsource, motion); } } #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, num_bl; VP9_COMMON *const cm = &cpi->common; uint8_t *y; const uint8_t *src_y = cpi->Source->y_buffer; const uint8_t *src_u = cpi->Source->u_buffer; 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 = 0; YV12_BUFFER_CONFIG skinmap; memset(&skinmap, 0, sizeof(YV12_BUFFER_CONFIG)); if (vpx_alloc_frame_buffer(&skinmap, cm->width, cm->height, cm->subsampling_x, cm->subsampling_y, VP9_ENC_BORDER_IN_PIXELS, cm->byte_alignment)) { vpx_free_frame_buffer(&skinmap); return; } memset(skinmap.buffer_alloc, 128, skinmap.frame_size); y = skinmap.y_buffer; // 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 += fac) { num_bl = 0; for (mi_col = 0; mi_col < cm->mi_cols - 1; mi_col += fac) { int is_skin = 0; if (mode_filter == 1) { // Use 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)]; ysource = (ysource + ysource2 + ysource3 + ysource4) >> 2; usource = (usource + usource2 + usource3 + usource4) >> 2; vsource = (vsource + vsource2 + vsource3 + vsource4) >> 2; is_skin = vp9_skin_pixel(ysource, usource, vsource, 1); } else { int block_size = BLOCK_8X8; int consec_zeromv = 0; int bl_index = mi_row * cm->mi_cols + mi_col; int bl_index1 = bl_index + 1; int bl_index2 = bl_index + cm->mi_cols; int bl_index3 = bl_index2 + 1; if (y_bsize == 8) consec_zeromv = cpi->consec_zero_mv[bl_index]; else consec_zeromv = VPXMIN(cpi->consec_zero_mv[bl_index], VPXMIN(cpi->consec_zero_mv[bl_index1], VPXMIN(cpi->consec_zero_mv[bl_index2], cpi->consec_zero_mv[bl_index3]))); if (y_bsize == 16) block_size = BLOCK_16X16; is_skin = vp9_compute_skin_block(src_y, src_u, src_v, src_ystride, src_uvstride, block_size, consec_zeromv, 0); } for (i = 0; i < y_bsize; i++) { for (j = 0; j < y_bsize; j++) { if (is_skin) y[i * src_ystride + j] = 255; else y[i * src_ystride + j] = src_y[i * src_ystride + j]; } } num_bl++; y += y_bsize; src_y += y_bsize; src_u += uv_bsize; src_v += uv_bsize; } 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); } #endif