vp9_ssim.c

/*
 *  Copyright (c) 2010 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 "vp9/encoder/vp9_onyx_int.h"

void vp9_ssim_parms_16x16_c(uint8_t *s, int sp, uint8_t *r,
                            int rp, unsigned long *sum_s, unsigned long *sum_r,
                            unsigned long *sum_sq_s, unsigned long *sum_sq_r,
                            unsigned long *sum_sxr) {
  int i, j;
  for (i = 0; i < 16; i++, s += sp, r += rp) {
    for (j = 0; j < 16; j++) {
      *sum_s += s[j];
      *sum_r += r[j];
      *sum_sq_s += s[j] * s[j];
      *sum_sq_r += r[j] * r[j];
      *sum_sxr += s[j] * r[j];
    }
  }
}
void vp9_ssim_parms_8x8_c(uint8_t *s, int sp, uint8_t *r, int rp,
                          unsigned long *sum_s, unsigned long *sum_r,
                          unsigned long *sum_sq_s, unsigned long *sum_sq_r,
                          unsigned long *sum_sxr) {
  int i, j;
  for (i = 0; i < 8; i++, s += sp, r += rp) {
    for (j = 0; j < 8; j++) {
      *sum_s += s[j];
      *sum_r += r[j];
      *sum_sq_s += s[j] * s[j];
      *sum_sq_r += r[j] * r[j];
      *sum_sxr += s[j] * r[j];
    }
  }
}

const static int64_t cc1 =  26634; // (64^2*(.01*255)^2
const static int64_t cc2 = 239708; // (64^2*(.03*255)^2

static double similarity(unsigned long sum_s, unsigned long sum_r,
                         unsigned long sum_sq_s, unsigned long sum_sq_r,
                         unsigned long sum_sxr, int count) {
  int64_t ssim_n, ssim_d;
  int64_t c1, c2;

  // scale the constants by number of pixels
  c1 = (cc1 * count * count) >> 12;
  c2 = (cc2 * count * count) >> 12;

  ssim_n = (2 * sum_s * sum_r + c1) * ((int64_t) 2 * count * sum_sxr -
                                       (int64_t) 2 * sum_s * sum_r + c2);

  ssim_d = (sum_s * sum_s + sum_r * sum_r + c1) *
           ((int64_t)count * sum_sq_s - (int64_t)sum_s * sum_s +
            (int64_t)count * sum_sq_r - (int64_t) sum_r * sum_r + c2);

  return ssim_n * 1.0 / ssim_d;
}

static double ssim_16x16(uint8_t *s, int sp, uint8_t *r, int rp) {
  unsigned long sum_s = 0, sum_r = 0, sum_sq_s = 0, sum_sq_r = 0, sum_sxr = 0;
  vp9_ssim_parms_16x16(s, sp, r, rp, &sum_s, &sum_r, &sum_sq_s, &sum_sq_r,