/*
 *  Copyright (c) 2014 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 <assert.h>
#include <limits.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>

#if CONFIG_VP9_HIGHBITDEPTH
#include "vpx_dsp/vpx_dsp_common.h"
#endif  // CONFIG_VP9_HIGHBITDEPTH
#include "vpx_ports/mem.h"
#include "vp10/common/common.h"
#include "vp10/encoder/resize.h"

#define FILTER_BITS               7

#define INTERP_TAPS               8
#define SUBPEL_BITS               5
#define SUBPEL_MASK               ((1 << SUBPEL_BITS) - 1)
#define INTERP_PRECISION_BITS     32

typedef int16_t interp_kernel[INTERP_TAPS];

// Filters for interpolation (0.5-band) - note this also filters integer pels.
static const interp_kernel filteredinterp_filters500[(1 << SUBPEL_BITS)] = {
  {-3,  0, 35, 64, 35,  0, -3, 0},
  {-3, -1, 34, 64, 36,  1, -3, 0},
  {-3, -1, 32, 64, 38,  1, -3, 0},
  {-2, -2, 31, 63, 39,  2, -3, 0},
  {-2, -2, 29, 63, 41,  2, -3, 0},
  {-2, -2, 28, 63, 42,  3, -4, 0},
  {-2, -3, 27, 63, 43,  4, -4, 0},
  {-2, -3, 25, 62, 45,  5, -4, 0},
  {-2, -3, 24, 62, 46,  5, -4, 0},
  {-2, -3, 23, 61, 47,  6, -4, 0},
  {-2, -3, 21, 60, 49,  7, -4, 0},
  {-1, -4, 20, 60, 50,  8, -4, -1},
  {-1, -4, 19, 59, 51,  9, -4, -1},
  {-1, -4, 17, 58, 52, 10, -4, 0},
  {-1, -4, 16, 57, 53, 12, -4, -1},
  {-1, -4, 15, 56, 54, 13, -4, -1},
  {-1, -4, 14, 55, 55, 14, -4, -1},
  {-1, -4, 13, 54, 56, 15, -4, -1},
  {-1, -4, 12, 53, 57, 16, -4, -1},
  {0, -4, 10, 52, 58, 17, -4, -1},
  {-1, -4,  9, 51, 59, 19, -4, -1},
  {-1, -4,  8, 50, 60, 20, -4, -1},
  {0, -4,  7, 49, 60, 21, -3, -2},
  {0, -4,  6, 47, 61, 23, -3, -2},
  {0, -4,  5, 46, 62, 24, -3, -2},
  {0, -4,  5, 45, 62, 25, -3, -2},
  {0, -4,  4, 43, 63, 27, -3, -2},
  {0, -4,  3, 42, 63, 28, -2, -2},
  {0, -3,  2, 41, 63, 29, -2, -2},
  {0, -3,  2, 39, 63, 31, -2, -2},
  {0, -3,  1, 38, 64, 32, -1, -3},
  {0, -3,  1, 36, 64, 34, -1, -3}
};

// Filters for interpolation (0.625-band) - note this also filters integer pels.
static const interp_kernel filteredinterp_filters625[(1 << SUBPEL_BITS)] = {
  {-1, -8, 33, 80, 33, -8, -1, 0},
  {-1, -8, 30, 80, 35, -8, -1, 1},
  {-1, -8, 28, 80, 37, -7, -2, 1},
  {0, -8, 26, 79, 39, -7, -2, 1},
  {0, -8, 24, 79, 41, -7, -2, 1},
  {0, -8, 22, 78, 43, -6, -2, 1},
  {0, -8, 20, 78, 45, -5, -3, 1},
  {0, -8, 18, 77, 48, -5, -3, 1},
  {0, -8, 16, 76, 50, -4, -3, 1},
  {0, -8, 15, 75, 52, -3, -4, 1},
  {0, -7, 13, 74, 54, -3, -4, 1},
  {0, -7, 11, 73, 56, -2, -4, 1},
  {0, -7, 10, 71, 58, -1, -4, 1},
  {1, -7,  8, 70, 60,  0, -5, 1},
  {1, -6,  6, 68, 62,  1, -5, 1},
  {1, -6,  5, 67, 63,  2, -5, 1},
  {1, -6,  4, 65, 65,  4, -6, 1},
  {1, -5,  2, 63, 67,  5, -6, 1},
  {1, -5,  1, 62, 68,  6, -6, 1},
  {1, -5,  0, 60, 70,  8, -7, 1},
  {1, -4, -1, 58, 71, 10, -7, 0},
  {1, -4, -2, 56, 73, 11, -7, 0},
  {1, -4, -3, 54, 74, 13, -7, 0},
  {1, -4, -3, 52, 75, 15, -8, 0},
  {1, -3, -4, 50, 76, 16, -8, 0},
  {1, -3, -5, 48, 77, 18, -8, 0},
  {1, -3, -5, 45, 78, 20, -8, 0},
  {1, -2, -6, 43, 78, 22, -8, 0},
  {1, -2, -7, 41, 79, 24, -8, 0},
  {1, -2, -7, 39, 79, 26, -8, 0},
  {1, -2, -7, 37, 80, 28, -8, -1},
  {1, -1, -8, 35, 80, 30, -8, -1},
};

// Filters for interpolation (0.75-band) - note this also filters integer pels.
static const interp_kernel filteredinterp_filters750[(1 << SUBPEL_BITS)] = {
  {2, -11,  25,  96,  25, -11,   2, 0},
  {2, -11,  22,  96,  28, -11,   2, 0},
  {2, -10,  19,  95,  31, -11,   2, 0},
  {2, -10,  17,  95,  34, -12,   2, 0},
  {2,  -9,  14,  94,  37, -12,   2, 0},
  {2,  -8,  12,  93,  40, -12,   1, 0},
  {2,  -8,   9,  92,  43, -12,   1, 1},
  {2,  -7,   7,  91,  46, -12,   1, 0},
  {2,  -7,   5,  90,  49, -12,   1, 0},
  {2,  -6,   3,  88,  52, -12,   0, 1},
  {2,  -5,   1,  86,  55, -12,   0, 1},
  {2,  -5,  -1,  84,  58, -11,   0, 1},
  {2,  -4,  -2,  82,  61, -11,  -1, 1},
  {2,  -4,  -4,  80,  64, -10,  -1, 1},
  {1, -3, -5, 77, 67, -9, -1, 1},
  {1, -3, -6, 75, 70, -8, -2, 1},
  {1, -2, -7, 72, 72, -7, -2, 1},
  {1, -2, -8, 70, 75, -6, -3, 1},
  {1, -1, -9, 67, 77, -5, -3, 1},
  {1,  -1, -10,  64,  80,  -4,  -4, 2},
  {1,  -1, -11,  61,  82,  -2,  -4, 2},
  {1,   0, -11,  58,  84,  -1,  -5, 2},
  {1,   0, -12,  55,  86,   1,  -5, 2},
  {1,   0, -12,  52,  88,   3,  -6, 2},
  {0,   1, -12,  49,  90,   5,  -7, 2},
  {0,   1, -12,  46,  91,   7,  -7, 2},
  {1,   1, -12,  43,  92,   9,  -8, 2},
  {0,   1, -12,  40,  93,  12,  -8, 2},
  {0,   2, -12,  37,  94,  14,  -9, 2},
  {0,   2, -12,  34,  95,  17, -10, 2},
  {0,   2, -11,  31,  95,  19, -10, 2},
  {0,   2, -11,  28,  96,  22, -11, 2}
};

// Filters for interpolation (0.875-band) - note this also filters integer pels.
static const interp_kernel filteredinterp_filters875[(1 << SUBPEL_BITS)] = {
  {3,  -8,  13, 112,  13,  -8,   3, 0},
  {3,  -7,  10, 112,  17,  -9,   3, -1},
  {2,  -6,   7, 111,  21,  -9,   3, -1},
  {2,  -5,   4, 111,  24, -10,   3, -1},
  {2,  -4,   1, 110,  28, -11,   3, -1},
  {1,  -3,  -1, 108,  32, -12,   4, -1},
  {1,  -2,  -3, 106,  36, -13,   4, -1},
  {1,  -1,  -6, 105,  40, -14,   4, -1},
  {1,  -1,  -7, 102,  44, -14,   4, -1},
  {1,   0,  -9, 100,  48, -15,   4, -1},
  {1,   1, -11,  97,  53, -16,   4, -1},
  {0,   1, -12,  95,  57, -16,   4, -1},
  {0,   2, -13,  91,  61, -16,   4, -1},
  {0,   2, -14,  88,  65, -16,   4, -1},
  {0,   3, -15,  84,  69, -17,   4, 0},
  {0,   3, -16,  81,  73, -16,   3, 0},
  {0,   3, -16,  77,  77, -16,   3, 0},
  {0,   3, -16,  73,  81, -16,   3, 0},
  {0,   4, -17,  69,  84, -15,   3, 0},
  {-1,   4, -16,  65,  88, -14,   2, 0},
  {-1,   4, -16,  61,  91, -13,   2, 0},
  {-1,   4, -16,  57,  95, -12,   1, 0},
  {-1,   4, -16,  53,  97, -11,   1, 1},
  {-1,   4, -15,  48, 100,  -9,   0, 1},
  {-1,   4, -14,  44, 102,  -7,  -1, 1},
  {-1,   4, -14,  40, 105,  -6,  -1, 1},
  {-1,   4, -13,  36, 106,  -3,  -2, 1},
  {-1,   4, -12,  32, 108,  -1,  -3, 1},
  {-1,   3, -11,  28, 110,   1,  -4, 2},
  {-1,   3, -10,  24, 111,   4,  -5, 2},
  {-1,   3,  -9,  21, 111,   7,  -6, 2},
  {-1,   3,  -9,  17, 112,  10,  -7, 3}
};

// Filters for interpolation (full-band) - no filtering for integer pixels
static const interp_kernel filteredinterp_filters1000[(1 << SUBPEL_BITS)] = {
  {0,   0,   0, 128,   0,   0,   0, 0},
  {0,   1,  -3, 128,   3,  -1,   0, 0},
  {-1,   2,  -6, 127,   7,  -2,   1, 0},
  {-1,   3,  -9, 126,  12,  -4,   1, 0},
  {-1,   4, -12, 125,  16,  -5,   1, 0},
  {-1,   4, -14, 123,  20,  -6,   2, 0},
  {-1,   5, -15, 120,  25,  -8,   2, 0},
  {-1,   5, -17, 118,  30,  -9,   3, -1},
  {-1,   6, -18, 114,  35, -10,   3, -1},
  {-1,   6, -19, 111,  41, -12,   3, -1},
  {-1,   6, -20, 107,  46, -13,   4, -1},
  {-1,   6, -21, 103,  52, -14,   4, -1},
  {-1,   6, -21,  99,  57, -16,   5, -1},
  {-1,   6, -21,  94,  63, -17,   5, -1},
  {-1,   6, -20,  89,  68, -18,   5, -1},
  {-1,   6, -20,  84,  73, -19,   6, -1},
  {-1,   6, -20,  79,  79, -20,   6, -1},
  {-1,   6, -19,  73,  84, -20,   6, -1},
  {-1,   5, -18,  68,  89, -20,   6, -1},
  {-1,   5, -17,  63,  94, -21,   6, -1},
  {-1,   5, -16,  57,  99, -21,   6, -1},
  {-1,   4, -14,  52, 103, -21,   6, -1},
  {-1,   4, -13,  46, 107, -20,   6, -1},
  {-1,   3, -12,  41, 111, -19,   6, -1},
  {-1,   3, -10,  35, 114, -18,   6, -1},
  {-1,   3,  -9,  30, 118, -17,   5, -1},
  {0,   2,  -8,  25, 120, -15,   5, -1},
  {0,   2,  -6,  20, 123, -14,   4, -1},
  {0,   1,  -5,  16, 125, -12,   4, -1},
  {0,   1,  -4,  12, 126,  -9,   3, -1},
  {0,   1,  -2,   7, 127,  -6,   2, -1},
  {0,   0,  -1,   3, 128,  -3,   1, 0}
};

// Filters for factor of 2 downsampling.
static const int16_t vp10_down2_symeven_half_filter[] = {56, 12, -3, -1};
static const int16_t vp10_down2_symodd_half_filter[] = {64, 35, 0, -3};

static const interp_kernel *choose_interp_filter(int inlength, int outlength) {
  int outlength16 = outlength * 16;
  if (outlength16 >= inlength * 16)
    return filteredinterp_filters1000;
  else if (outlength16 >= inlength * 13)
    return filteredinterp_filters875;
  else if (outlength16 >= inlength * 11)
    return filteredinterp_filters750;
  else if (outlength16 >= inlength * 9)
    return filteredinterp_filters625;
  else
    return filteredinterp_filters500;
}

static void interpolate(const uint8_t *const input, int inlength,
                        uint8_t *output, int outlength) {
  const int64_t delta = (((uint64_t)inlength << 32) + outlength / 2) /
      outlength;
  const int64_t offset = inlength > outlength ?
      (((int64_t)(inlength - outlength) << 31) + outlength / 2) / outlength :
      -(((int64_t)(outlength - inlength) << 31) + outlength / 2) / outlength;
  uint8_t *optr = output;
  int x, x1, x2, sum, k, int_pel, sub_pel;
  int64_t y;

  const interp_kernel *interp_filters =
      choose_interp_filter(inlength, outlength);

  x = 0;
  y = offset;
  while ((y >> INTERP_PRECISION_BITS) < (INTERP_TAPS / 2 - 1)) {
    x++;
    y += delta;
  }
  x1 = x;
  x = outlength - 1;
  y = delta * x + offset;
  while ((y >> INTERP_PRECISION_BITS) +
         (int64_t)(INTERP_TAPS / 2) >= inlength) {
    x--;
    y -= delta;
  }
  x2 = x;
  if (x1 > x2) {
    for (x = 0, y = offset; x < outlength; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k) {
        const int pk = int_pel - INTERP_TAPS / 2 + 1 + k;
        sum += filter[k] * input[(pk < 0 ? 0 :
                                  (pk >= inlength ? inlength - 1 : pk))];
      }
      *optr++ = clip_pixel(ROUND_POWER_OF_TWO(sum, FILTER_BITS));
    }
  } else {
    // Initial part.
    for (x = 0, y = offset; x < x1; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k)
        sum += filter[k] * input[(int_pel - INTERP_TAPS / 2 + 1 + k < 0 ?
                                  0 :
                                  int_pel - INTERP_TAPS / 2 + 1 + k)];
      *optr++ = clip_pixel(ROUND_POWER_OF_TWO(sum, FILTER_BITS));
    }
    // Middle part.
    for (; x <= x2; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k)
        sum += filter[k] * input[int_pel - INTERP_TAPS / 2 + 1 + k];
      *optr++ = clip_pixel(ROUND_POWER_OF_TWO(sum, FILTER_BITS));
    }
    // End part.
    for (; x < outlength; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k)
        sum += filter[k] * input[(int_pel - INTERP_TAPS / 2 + 1 + k >=
                                  inlength ?  inlength - 1 :
                                  int_pel - INTERP_TAPS / 2 + 1 + k)];
      *optr++ = clip_pixel(ROUND_POWER_OF_TWO(sum, FILTER_BITS));
    }
  }
}

static void down2_symeven(const uint8_t *const input, int length,
                          uint8_t *output) {
  // Actual filter len = 2 * filter_len_half.
  const int16_t *filter = vp10_down2_symeven_half_filter;
  const int filter_len_half = sizeof(vp10_down2_symeven_half_filter) / 2;
  int i, j;
  uint8_t *optr = output;
  int l1 = filter_len_half;
  int l2 = (length - filter_len_half);
  l1 += (l1 & 1);
  l2 += (l2 & 1);
  if (l1 > l2) {
    // Short input length.
    for (i = 0; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] +
                input[(i + 1 + j >= length ? length - 1 : i + 1 + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
  } else {
    // Initial part.
    for (i = 0; i < l1; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] + input[i + 1 + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
    // Middle part.
    for (; i < l2; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[i - j] + input[i + 1 + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
    // End part.
    for (; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[i - j] +
                input[(i + 1 + j >= length ? length - 1 : i + 1 + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
  }
}

static void down2_symodd(const uint8_t *const input, int length,
                         uint8_t *output) {
  // Actual filter len = 2 * filter_len_half - 1.
  const int16_t *filter = vp10_down2_symodd_half_filter;
  const int filter_len_half = sizeof(vp10_down2_symodd_half_filter) / 2;
  int i, j;
  uint8_t *optr = output;
  int l1 = filter_len_half - 1;
  int l2 = (length - filter_len_half + 1);
  l1 += (l1 & 1);
  l2 += (l2 & 1);
  if (l1 > l2) {
    // Short input length.
    for (i = 0; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] +
                input[(i + j >= length ? length - 1 : i + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
  } else {
    // Initial part.
    for (i = 0; i < l1; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] + input[i + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
    // Middle part.
    for (; i < l2; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[i - j] + input[i + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
    // End part.
    for (; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[i - j] + input[(i + j >= length ? length - 1 : i + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel(sum);
    }
  }
}

static int get_down2_length(int length, int steps) {
  int s;
  for (s = 0; s < steps; ++s)
    length = (length + 1) >> 1;
  return length;
}

static int get_down2_steps(int in_length, int out_length) {
  int steps = 0;
  int proj_in_length;
  while ((proj_in_length = get_down2_length(in_length, 1)) >= out_length) {
    ++steps;
    in_length = proj_in_length;
  }
  return steps;
}

static void resize_multistep(const uint8_t *const input,
                             int length,
                             uint8_t *output,
                             int olength,
                             uint8_t *otmp) {
  int steps;
  if (length == olength) {
    memcpy(output, input, sizeof(output[0]) * length);
    return;
  }
  steps = get_down2_steps(length, olength);

  if (steps > 0) {
    int s;
    uint8_t *out = NULL;
    uint8_t *otmp2;
    int filteredlength = length;

    assert(otmp != NULL);
    otmp2 = otmp + get_down2_length(length, 1);
    for (s = 0; s < steps; ++s) {
      const int proj_filteredlength = get_down2_length(filteredlength, 1);
      const uint8_t *const in = (s == 0 ? input : out);
      if (s == steps - 1 && proj_filteredlength == olength)
        out = output;
      else
        out = (s & 1 ? otmp2 : otmp);
      if (filteredlength & 1)
        down2_symodd(in, filteredlength, out);
      else
        down2_symeven(in, filteredlength, out);
      filteredlength = proj_filteredlength;
    }
    if (filteredlength != olength) {
      interpolate(out, filteredlength, output, olength);
    }
  } else {
    interpolate(input, length, output, olength);
  }
}

static void fill_col_to_arr(uint8_t *img, int stride, int len, uint8_t *arr) {
  int i;
  uint8_t *iptr = img;
  uint8_t *aptr = arr;
  for (i = 0; i < len; ++i, iptr += stride) {
    *aptr++ = *iptr;
  }
}

static void fill_arr_to_col(uint8_t *img, int stride, int len, uint8_t *arr) {
  int i;
  uint8_t *iptr = img;
  uint8_t *aptr = arr;
  for (i = 0; i < len; ++i, iptr += stride) {
    *iptr = *aptr++;
  }
}

void vp10_resize_plane(const uint8_t *const input,
                      int height,
                      int width,
                      int in_stride,
                      uint8_t *output,
                      int height2,
                      int width2,
                      int out_stride) {
  int i;
  uint8_t *intbuf = (uint8_t *)malloc(sizeof(uint8_t) * width2 * height);
  uint8_t *tmpbuf = (uint8_t *)malloc(sizeof(uint8_t) *
                                      (width < height ? height : width));
  uint8_t *arrbuf = (uint8_t *)malloc(sizeof(uint8_t) * height);
  uint8_t *arrbuf2 = (uint8_t *)malloc(sizeof(uint8_t) * height2);
  if (intbuf == NULL || tmpbuf == NULL ||
      arrbuf == NULL || arrbuf2 == NULL)
    goto Error;
  assert(width > 0);
  assert(height > 0);
  assert(width2 > 0);
  assert(height2 > 0);
  for (i = 0; i < height; ++i)
    resize_multistep(input + in_stride * i, width,
                        intbuf + width2 * i, width2, tmpbuf);
  for (i = 0; i < width2; ++i) {
    fill_col_to_arr(intbuf + i, width2, height, arrbuf);
    resize_multistep(arrbuf, height, arrbuf2, height2, tmpbuf);
    fill_arr_to_col(output + i, out_stride, height2, arrbuf2);
  }

 Error:
  free(intbuf);
  free(tmpbuf);
  free(arrbuf);
  free(arrbuf2);
}

#if CONFIG_VP9_HIGHBITDEPTH
static void highbd_interpolate(const uint16_t *const input, int inlength,
                               uint16_t *output, int outlength, int bd) {
  const int64_t delta =
      (((uint64_t)inlength << 32) + outlength / 2) / outlength;
  const int64_t offset = inlength > outlength ?
      (((int64_t)(inlength - outlength) << 31) + outlength / 2) / outlength :
      -(((int64_t)(outlength - inlength) << 31) + outlength / 2) / outlength;
  uint16_t *optr = output;
  int x, x1, x2, sum, k, int_pel, sub_pel;
  int64_t y;

  const interp_kernel *interp_filters =
      choose_interp_filter(inlength, outlength);

  x = 0;
  y = offset;
  while ((y >> INTERP_PRECISION_BITS) < (INTERP_TAPS / 2 - 1)) {
    x++;
    y += delta;
  }
  x1 = x;
  x = outlength - 1;
  y = delta * x + offset;
  while ((y >> INTERP_PRECISION_BITS) +
         (int64_t)(INTERP_TAPS / 2) >= inlength) {
    x--;
    y -= delta;
  }
  x2 = x;
  if (x1 > x2) {
    for (x = 0, y = offset; x < outlength; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k) {
        const int pk = int_pel - INTERP_TAPS / 2 + 1 + k;
        sum += filter[k] *
            input[(pk < 0 ? 0 : (pk >= inlength ? inlength - 1 : pk))];
      }
      *optr++ = clip_pixel_highbd(ROUND_POWER_OF_TWO(sum, FILTER_BITS), bd);
    }
  } else {
    // Initial part.
    for (x = 0, y = offset; x < x1; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k)
        sum += filter[k] *
            input[(int_pel - INTERP_TAPS / 2 + 1 + k < 0 ?
                   0 : int_pel - INTERP_TAPS / 2 + 1 + k)];
      *optr++ = clip_pixel_highbd(ROUND_POWER_OF_TWO(sum, FILTER_BITS), bd);
    }
    // Middle part.
    for (; x <= x2; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k)
        sum += filter[k] * input[int_pel - INTERP_TAPS / 2 + 1 + k];
      *optr++ = clip_pixel_highbd(ROUND_POWER_OF_TWO(sum, FILTER_BITS), bd);
    }
    // End part.
    for (; x < outlength; ++x, y += delta) {
      const int16_t *filter;
      int_pel = y >> INTERP_PRECISION_BITS;
      sub_pel = (y >> (INTERP_PRECISION_BITS - SUBPEL_BITS)) & SUBPEL_MASK;
      filter = interp_filters[sub_pel];
      sum = 0;
      for (k = 0; k < INTERP_TAPS; ++k)
        sum += filter[k] * input[(int_pel - INTERP_TAPS / 2 + 1 + k >=
                                  inlength ?  inlength - 1 :
                                  int_pel - INTERP_TAPS / 2 + 1 + k)];
      *optr++ = clip_pixel_highbd(ROUND_POWER_OF_TWO(sum, FILTER_BITS), bd);
    }
  }
}

static void highbd_down2_symeven(const uint16_t *const input, int length,
                                 uint16_t *output, int bd) {
  // Actual filter len = 2 * filter_len_half.
  static const int16_t *filter = vp10_down2_symeven_half_filter;
  const int filter_len_half = sizeof(vp10_down2_symeven_half_filter) / 2;
  int i, j;
  uint16_t *optr = output;
  int l1 = filter_len_half;
  int l2 = (length - filter_len_half);
  l1 += (l1 & 1);
  l2 += (l2 & 1);
  if (l1 > l2) {
    // Short input length.
    for (i = 0; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] +
                input[(i + 1 + j >= length ? length - 1 : i + 1 + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
  } else {
    // Initial part.
    for (i = 0; i < l1; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] + input[i + 1 + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
    // Middle part.
    for (; i < l2; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[i - j] + input[i + 1 + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
    // End part.
    for (; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1));
      for (j = 0; j < filter_len_half; ++j) {
        sum += (input[i - j] +
                input[(i + 1 + j >= length ? length - 1 : i + 1 + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
  }
}

static void highbd_down2_symodd(const uint16_t *const input, int length,
                              uint16_t *output, int bd) {
  // Actual filter len = 2 * filter_len_half - 1.
  static const int16_t *filter = vp10_down2_symodd_half_filter;
  const int filter_len_half = sizeof(vp10_down2_symodd_half_filter) / 2;
  int i, j;
  uint16_t *optr = output;
  int l1 = filter_len_half - 1;
  int l2 = (length - filter_len_half + 1);
  l1 += (l1 & 1);
  l2 += (l2 & 1);
  if (l1 > l2) {
    // Short input length.
    for (i = 0; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] +
                input[(i + j >= length ? length - 1 : i + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
  } else {
    // Initial part.
    for (i = 0; i < l1; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[(i - j < 0 ? 0 : i - j)] + input[i + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
    // Middle part.
    for (; i < l2; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[i - j] + input[i + j]) * filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
    // End part.
    for (; i < length; i += 2) {
      int sum = (1 << (FILTER_BITS - 1)) + input[i] * filter[0];
      for (j = 1; j < filter_len_half; ++j) {
        sum += (input[i - j] + input[(i + j >= length ? length - 1 : i + j)]) *
            filter[j];
      }
      sum >>= FILTER_BITS;
      *optr++ = clip_pixel_highbd(sum, bd);
    }
  }
}

static void highbd_resize_multistep(const uint16_t *const input,
                                    int length,
                                    uint16_t *output,
                                    int olength,
                                    uint16_t *otmp,
                                    int bd) {
  int steps;
  if (length == olength) {
    memcpy(output, input, sizeof(output[0]) * length);
    return;
  }
  steps = get_down2_steps(length, olength);

  if (steps > 0) {
    int s;
    uint16_t *out = NULL;
    uint16_t *otmp2;
    int filteredlength = length;

    assert(otmp != NULL);
    otmp2 = otmp + get_down2_length(length, 1);
    for (s = 0; s < steps; ++s) {
      const int proj_filteredlength = get_down2_length(filteredlength, 1);
      const uint16_t *const in = (s == 0 ? input : out);
      if (s == steps - 1 && proj_filteredlength == olength)
        out = output;
      else
        out = (s & 1 ? otmp2 : otmp);
      if (filteredlength & 1)
        highbd_down2_symodd(in, filteredlength, out, bd);
      else
        highbd_down2_symeven(in, filteredlength, out, bd);
      filteredlength = proj_filteredlength;
    }
    if (filteredlength != olength) {
      highbd_interpolate(out, filteredlength, output, olength, bd);
    }
  } else {
    highbd_interpolate(input, length, output, olength, bd);
  }
}

static void highbd_fill_col_to_arr(uint16_t *img, int stride, int len,
                                   uint16_t *arr) {
  int i;
  uint16_t *iptr = img;
  uint16_t *aptr = arr;
  for (i = 0; i < len; ++i, iptr += stride) {
    *aptr++ = *iptr;
  }
}

static void highbd_fill_arr_to_col(uint16_t *img, int stride, int len,
                                   uint16_t *arr) {
  int i;
  uint16_t *iptr = img;
  uint16_t *aptr = arr;
  for (i = 0; i < len; ++i, iptr += stride) {
    *iptr = *aptr++;
  }
}

void vp10_highbd_resize_plane(const uint8_t *const input,
                             int height,
                             int width,
                             int in_stride,
                             uint8_t *output,
                             int height2,
                             int width2,
                             int out_stride,
                             int bd) {
  int i;
  uint16_t *intbuf = (uint16_t *)malloc(sizeof(uint16_t) * width2 * height);
  uint16_t *tmpbuf = (uint16_t *)malloc(sizeof(uint16_t) *
                                        (width < height ? height : width));
  uint16_t *arrbuf = (uint16_t *)malloc(sizeof(uint16_t) * height);
  uint16_t *arrbuf2 = (uint16_t *)malloc(sizeof(uint16_t) * height2);
  if (intbuf == NULL || tmpbuf == NULL ||
      arrbuf == NULL || arrbuf2 == NULL) goto Error;
  for (i = 0; i < height; ++i) {
    highbd_resize_multistep(CONVERT_TO_SHORTPTR(input + in_stride * i), width,
                            intbuf + width2 * i, width2, tmpbuf, bd);
  }
  for (i = 0; i < width2; ++i) {
    highbd_fill_col_to_arr(intbuf + i, width2, height, arrbuf);
    highbd_resize_multistep(arrbuf, height, arrbuf2, height2, tmpbuf,
                            bd);
    highbd_fill_arr_to_col(CONVERT_TO_SHORTPTR(output + i), out_stride, height2,
                           arrbuf2);
  }

 Error:
  free(intbuf);
  free(tmpbuf);
  free(arrbuf);
  free(arrbuf2);
}
#endif  // CONFIG_VP9_HIGHBITDEPTH

void vp10_resize_frame420(const uint8_t *const y,
                         int y_stride,
                         const uint8_t *const u, const uint8_t *const v,
                         int uv_stride,
                         int height, int width,
                         uint8_t *oy, int oy_stride,
                         uint8_t *ou, uint8_t *ov, int ouv_stride,
                         int oheight, int owidth) {
  vp10_resize_plane(y, height, width, y_stride,
                   oy, oheight, owidth, oy_stride);
  vp10_resize_plane(u, height / 2, width / 2, uv_stride,
                   ou, oheight / 2, owidth / 2, ouv_stride);
  vp10_resize_plane(v, height / 2, width / 2, uv_stride,
                   ov, oheight / 2, owidth / 2, ouv_stride);
}

void vp10_resize_frame422(const uint8_t *const y, int y_stride,
                         const uint8_t *const u, const uint8_t *const v,
                         int uv_stride,
                         int height, int width,
                         uint8_t *oy, int oy_stride,
                         uint8_t *ou, uint8_t *ov, int ouv_stride,
                         int oheight, int owidth) {
  vp10_resize_plane(y, height, width, y_stride,
                   oy, oheight, owidth, oy_stride);
  vp10_resize_plane(u, height, width / 2, uv_stride,
                   ou, oheight, owidth / 2, ouv_stride);
  vp10_resize_plane(v, height, width / 2, uv_stride,
                   ov, oheight, owidth / 2, ouv_stride);
}

void vp10_resize_frame444(const uint8_t *const y, int y_stride,
                         const uint8_t *const u, const uint8_t *const v,
                         int uv_stride,
                         int height, int width,
                         uint8_t *oy, int oy_stride,
                         uint8_t *ou, uint8_t *ov, int ouv_stride,
                         int oheight, int owidth) {
  vp10_resize_plane(y, height, width, y_stride,
                   oy, oheight, owidth, oy_stride);
  vp10_resize_plane(u, height, width, uv_stride,
                   ou, oheight, owidth, ouv_stride);
  vp10_resize_plane(v, height, width, uv_stride,
                   ov, oheight, owidth, ouv_stride);
}

#if CONFIG_VP9_HIGHBITDEPTH
void vp10_highbd_resize_frame420(const uint8_t *const y,
                                int y_stride,
                                const uint8_t *const u, const uint8_t *const v,
                                int uv_stride,
                                int height, int width,
                                uint8_t *oy, int oy_stride,
                                uint8_t *ou, uint8_t *ov, int ouv_stride,
                                int oheight, int owidth, int bd) {
  vp10_highbd_resize_plane(y, height, width, y_stride,
                          oy, oheight, owidth, oy_stride, bd);
  vp10_highbd_resize_plane(u, height / 2, width / 2, uv_stride,
                          ou, oheight / 2, owidth / 2, ouv_stride, bd);
  vp10_highbd_resize_plane(v, height / 2, width / 2, uv_stride,
                          ov, oheight / 2, owidth / 2, ouv_stride, bd);
}

void vp10_highbd_resize_frame422(const uint8_t *const y, int y_stride,
                                const uint8_t *const u, const uint8_t *const v,
                                int uv_stride,
                                int height, int width,
                                uint8_t *oy, int oy_stride,
                                uint8_t *ou, uint8_t *ov, int ouv_stride,
                                int oheight, int owidth, int bd) {
  vp10_highbd_resize_plane(y, height, width, y_stride,
                          oy, oheight, owidth, oy_stride, bd);
  vp10_highbd_resize_plane(u, height, width / 2, uv_stride,
                          ou, oheight, owidth / 2, ouv_stride, bd);
  vp10_highbd_resize_plane(v, height, width / 2, uv_stride,
                          ov, oheight, owidth / 2, ouv_stride, bd);
}

void vp10_highbd_resize_frame444(const uint8_t *const y, int y_stride,
                                const uint8_t *const u, const uint8_t *const v,
                                int uv_stride,
                                int height, int width,
                                uint8_t *oy, int oy_stride,
                                uint8_t *ou, uint8_t *ov, int ouv_stride,
                                int oheight, int owidth, int bd) {
  vp10_highbd_resize_plane(y, height, width, y_stride,
                          oy, oheight, owidth, oy_stride, bd);
  vp10_highbd_resize_plane(u, height, width, uv_stride,
                          ou, oheight, owidth, ouv_stride, bd);
  vp10_highbd_resize_plane(v, height, width, uv_stride,
                          ov, oheight, owidth, ouv_stride, bd);
}
#endif  // CONFIG_VP9_HIGHBITDEPTH