vp9_variance.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_rtcd.h"

#include "vpx_ports/mem.h"
#include "vpx/vpx_integer.h"

#include "vp9/common/vp9_common.h"
#include "vp9/common/vp9_filter.h"

#include "vp9/encoder/vp9_variance.h"

void variance(const uint8_t *a, int  a_stride,
              const uint8_t *b, int  b_stride,
              int  w, int  h, unsigned int *sse, int *sum) {
  int i, j;

  *sum = 0;
  *sse = 0;

  for (i = 0; i < h; i++) {
    for (j = 0; j < w; j++) {
      const int diff = a[j] - b[j];
      *sum += diff;
      *sse += diff * diff;
    }

    a += a_stride;
    b += b_stride;
  }
}

// Applies a 1-D 2-tap bi-linear filter to the source block in either horizontal
// or vertical direction to produce the filtered output block. Used to implement
// first-pass of 2-D separable filter.
//
// Produces int32_t output to retain precision for next pass. Two filter taps
// should sum to VP9_FILTER_WEIGHT. pixel_step defines whether the filter is
// applied horizontally (pixel_step=1) or vertically (pixel_step=stride). It
// defines the offset required to move from one input to the next.
static void var_filter_block2d_bil_first_pass(const uint8_t *src_ptr,
                                              uint16_t *output_ptr,
                                              unsigned int src_pixels_per_line,
                                              int pixel_step,
                                              unsigned int output_height,
                                              unsigned int output_width,
                                              const int16_t *vp9_filter) {
  unsigned int i, j;

  for (i = 0; i < output_height; i++) {
    for (j = 0; j < output_width; j++) {
      output_ptr[j] = ROUND_POWER_OF_TWO((int)src_ptr[0] * vp9_filter[0] +
                          (int)src_ptr[pixel_step] * vp9_filter[1],
                          FILTER_BITS);

      src_ptr++;
    }

    // Next row...
    src_ptr    += src_pixels_per_line - output_width;
    output_ptr += output_width;
  }