text: /*
   *  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_VPX_HIGHBITDEPTH
  #include "vpx_dsp/vpx_dsp_common.h"
  #endif  // CONFIG_VPX_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 *buf) {
    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 *tmpbuf = NULL;
      uint8_t *otmp, *otmp2;
      int filteredlength = length;
      if (!tmpbuf) {
        tmpbuf = (uint8_t *)malloc(sizeof(uint8_t) * length);
        otmp = tmpbuf;
      } else {
        otmp = buf;
      }
      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);
      }
      if (tmpbuf) free(tmpbuf);
    } 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 + height2));
    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, arrbuf + height, height2, tmpbuf);
      fill_arr_to_col(output + i, out_stride, height2, arrbuf + height);
    }
    free(intbuf);
    free(tmpbuf);
    free(arrbuf);
  }
  
  #if CONFIG_VPX_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 *buf, 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 *tmpbuf = NULL;
      uint16_t *otmp, *otmp2;
      int filteredlength = length;
      if (!tmpbuf) {
        tmpbuf = (uint16_t *)malloc(sizeof(uint16_t) * length);
        otmp = tmpbuf;
      } else {
        otmp = buf;
      }
      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);
      }
      if (tmpbuf) free(tmpbuf);
    } 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 + height2));
    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, arrbuf + height, height2, tmpbuf,
                              bd);
      highbd_fill_arr_to_col(CONVERT_TO_SHORTPTR(output + i), out_stride, height2,
                             arrbuf + height);
    }
    free(intbuf);
    free(tmpbuf);
    free(arrbuf);
  }
  #endif  // CONFIG_VPX_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_VPX_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_VPX_HIGHBITDEPTH
  