src/third_party/libvpx/vp8/common/quant_common.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 "quant_common.h"

static const int dc_qlookup[QINDEX_RANGE] = {
  4,   5,   6,   7,   8,   9,   10,  10,  11,  12,  13,  14,  15,  16,  17,
  17,  18,  19,  20,  20,  21,  21,  22,  22,  23,  23,  24,  25,  25,  26,
  27,  28,  29,  30,  31,  32,  33,  34,  35,  36,  37,  37,  38,  39,  40,
  41,  42,  43,  44,  45,  46,  46,  47,  48,  49,  50,  51,  52,  53,  54,
  55,  56,  57,  58,  59,  60,  61,  62,  63,  64,  65,  66,  67,  68,  69,
  70,  71,  72,  73,  74,  75,  76,  76,  77,  78,  79,  80,  81,  82,  83,
  84,  85,  86,  87,  88,  89,  91,  93,  95,  96,  98,  100, 101, 102, 104,
  106, 108, 110, 112, 114, 116, 118, 122, 124, 126, 128, 130, 132, 134, 136,
  138, 140, 143, 145, 148, 151, 154, 157,
};

static const int ac_qlookup[QINDEX_RANGE] = {
  4,   5,   6,   7,   8,   9,   10,  11,  12,  13,  14,  15,  16,  17,  18,
  19,  20,  21,  22,  23,  24,  25,  26,  27,  28,  29,  30,  31,  32,  33,
  34,  35,  36,  37,  38,  39,  40,  41,  42,  43,  44,  45,  46,  47,  48,
  49,  50,  51,  52,  53,  54,  55,  56,  57,  58,  60,  62,  64,  66,  68,
  70,  72,  74,  76,  78,  80,  82,  84,  86,  88,  90,  92,  94,  96,  98,
  100, 102, 104, 106, 108, 110, 112, 114, 116, 119, 122, 125, 128, 131, 134,
  137, 140, 143, 146, 149, 152, 155, 158, 161, 164, 167, 170, 173, 177, 181,
  185, 189, 193, 197, 201, 205, 209, 213, 217, 221, 225, 229, 234, 239, 245,
  249, 254, 259, 264, 269, 274, 279, 284,
};

int vp8_dc_quant(int QIndex, int Delta) {
  int retval;

  QIndex = QIndex + Delta;

  if (QIndex > 127) {
    QIndex = 127;
  } else if (QIndex < 0) {
    QIndex = 0;
  }

  retval = dc_qlookup[QIndex];
  return retval;
}

int vp8_dc2quant(int QIndex, int Delta) {
  int retval;

  QIndex = QIndex + Delta;

  if (QIndex > 127) {
    QIndex = 127;
  } else if (QIndex < 0) {
    QIndex = 0;
  }

  retval = dc_qlookup[QIndex] * 2;
  return retval;
}
int vp8_dc_uv_quant(int QIndex, int Delta) {
  int retval;

  QIndex = QIndex + Delta;

  if (QIndex > 127) {
    QIndex = 127;
  } else if (QIndex < 0) {
    QIndex = 0;
  }

  retval = dc_qlookup[QIndex];

  if (retval > 132) retval = 132;

  return retval;
}

int vp8_ac_yquant(int QIndex) {
  int retval;

  if (QIndex > 127) {
    QIndex = 127;
  } else if (QIndex < 0) {
    QIndex = 0;
  }

  retval = ac_qlookup[QIndex];
  return retval;
}

int vp8_ac2quant(int QIndex, int Delta) {
  int retval;

  QIndex = QIndex + Delta;

  if (QIndex > 127) {
    QIndex = 127;
  } else if (QIndex < 0) {
    QIndex = 0;
  }

  /* For all x in [0..284], x*155/100 is bitwise equal to (x*101581) >> 16.
   * The smallest precision for that is '(x*6349) >> 12' but 16 is a good
   * word size. */
  retval = (ac_qlookup[QIndex] * 101581) >> 16;

  if (retval < 8) retval = 8;

  return retval;
}
int vp8_ac_uv_quant(int QIndex, int Delta) {
  int retval;

  QIndex = QIndex + Delta;

  if (QIndex > 127) {
    QIndex = 127;
  } else if (QIndex < 0) {
    QIndex = 0;
  }

  retval = ac_qlookup[QIndex];
  return retval;
}