vp8/common/idctllm.c

   1 /*
   2  *  Copyright (c) 2010 The WebM project authors. All Rights Reserved.
   3  *
   4  *  Use of this source code is governed by a BSD-style license
   5  *  that can be found in the LICENSE file in the root of the source
   6  *  tree. An additional intellectual property rights grant can be found
   7  *  in the file PATENTS.  All contributing project authors may
   8  *  be found in the AUTHORS file in the root of the source tree.
   9  */
  10
  11
  12 /****************************************************************************
  13  * Notes:
  14  *
  15  * This implementation makes use of 16 bit fixed point verio of two multiply
  16  * constants:
  17  *         1.   sqrt(2) * cos (pi/8)
  18  *         2.   sqrt(2) * sin (pi/8)
  19  * Becuase the first constant is bigger than 1, to maintain the same 16 bit
  20  * fixed point precision as the second one, we use a trick of
  21  *         x * a = x + x*(a-1)
  22  * so
  23  *         x * sqrt(2) * cos (pi/8) = x + x * (sqrt(2) *cos(pi/8)-1).
  24  **************************************************************************/
  25 static const int cospi8sqrt2minus1 = 20091;
  26 static const int sinpi8sqrt2      = 35468;
  27 static const int rounding = 0;
  28 void vp8_short_idct4x4llm_c(short *input, short *output, int pitch)
  29 {
  30     int i;
  31     int a1, b1, c1, d1;
  32
  33     short *ip = input;
  34     short *op = output;
  35     int temp1, temp2;
  36     int shortpitch = pitch >> 1;
  37
  38     for (i = 0; i < 4; i++)
  39     {
  40         a1 = ip[0] + ip[8];
  41         b1 = ip[0] - ip[8];
  42
  43         temp1 = (ip[4] * sinpi8sqrt2 + rounding) >> 16;
  44         temp2 = ip[12] + ((ip[12] * cospi8sqrt2minus1 + rounding) >> 16);
  45         c1 = temp1 - temp2;
  46
  47         temp1 = ip[4] + ((ip[4] * cospi8sqrt2minus1 + rounding) >> 16);
  48         temp2 = (ip[12] * sinpi8sqrt2 + rounding) >> 16;
  49         d1 = temp1 + temp2;
  50
  51         op[shortpitch*0] = a1 + d1;
  52         op[shortpitch*3] = a1 - d1;
  53
  54         op[shortpitch*1] = b1 + c1;
  55         op[shortpitch*2] = b1 - c1;
  56
  57         ip++;
  58         op++;
  59     }
  60
  61     ip = output;
  62     op = output;
  63
  64     for (i = 0; i < 4; i++)
  65     {
  66         a1 = ip[0] + ip[2];
  67         b1 = ip[0] - ip[2];
  68
  69         temp1 = (ip[1] * sinpi8sqrt2 + rounding) >> 16;
  70         temp2 = ip[3] + ((ip[3] * cospi8sqrt2minus1 + rounding) >> 16);
  71         c1 = temp1 - temp2;
  72
  73         temp1 = ip[1] + ((ip[1] * cospi8sqrt2minus1 + rounding) >> 16);
  74         temp2 = (ip[3] * sinpi8sqrt2 + rounding) >> 16;
  75         d1 = temp1 + temp2;
  76
  77
  78         op[0] = (a1 + d1 + 4) >> 3;
  79         op[3] = (a1 - d1 + 4) >> 3;
  80
  81         op[1] = (b1 + c1 + 4) >> 3;
  82         op[2] = (b1 - c1 + 4) >> 3;
  83
  84         ip += shortpitch;
  85         op += shortpitch;
  86     }
  87 }
  88
  89 void vp8_short_idct4x4llm_1_c(short *input, short *output, int pitch)
  90 {
  91     int i;
  92     int a1;
  93     short *op = output;
  94     int shortpitch = pitch >> 1;
  95     a1 = ((input[0] + 4) >> 3);
  96
  97     for (i = 0; i < 4; i++)
  98     {
  99         op[0] = a1;
 100         op[1] = a1;
 101         op[2] = a1;
 102         op[3] = a1;
 103         op += shortpitch;
 104     }
 105 }
 106
 107 void vp8_dc_only_idct_add_c(short input_dc, unsigned char *pred_ptr, unsigned char *dst_ptr, int pitch, int stride)
 108 {
 109     int a1 = ((input_dc + 4) >> 3);
 110     int r, c;
 111
 112     for (r = 0; r < 4; r++)
 113     {
 114         for (c = 0; c < 4; c++)
 115         {
 116             int a = a1 + pred_ptr[c] ;
 117
 118             if (a < 0)
 119                 a = 0;
 120
 121             if (a > 255)
 122                 a = 255;
 123
 124             dst_ptr[c] = (unsigned char) a ;
 125         }
 126
 127         dst_ptr += stride;
 128         pred_ptr += pitch;
 129     }
 130
 131 }
 132
 133 void vp8_short_inv_walsh4x4_c(short *input, short *output)
 134 {
 135     int i;
 136     int a1, b1, c1, d1;
 137     int a2, b2, c2, d2;
 138     short *ip = input;
 139     short *op = output;
 140
 141     for (i = 0; i < 4; i++)
 142     {
 143         a1 = ip[0] + ip[12];
 144         b1 = ip[4] + ip[8];
 145         c1 = ip[4] - ip[8];
 146         d1 = ip[0] - ip[12];
 147
 148         op[0] = a1 + b1;
 149         op[4] = c1 + d1;
 150         op[8] = a1 - b1;
 151         op[12] = d1 - c1;
 152         ip++;
 153         op++;
 154     }
 155
 156     ip = output;
 157     op = output;
 158
 159     for (i = 0; i < 4; i++)
 160     {
 161         a1 = ip[0] + ip[3];
 162         b1 = ip[1] + ip[2];
 163         c1 = ip[1] - ip[2];
 164         d1 = ip[0] - ip[3];
 165
 166         a2 = a1 + b1;
 167         b2 = c1 + d1;
 168         c2 = a1 - b1;
 169         d2 = d1 - c1;
 170
 171         op[0] = (a2 + 3) >> 3;
 172         op[1] = (b2 + 3) >> 3;
 173         op[2] = (c2 + 3) >> 3;
 174         op[3] = (d2 + 3) >> 3;
 175
 176         ip += 4;
 177         op += 4;
 178     }
 179 }
 180
 181 void vp8_short_inv_walsh4x4_1_c(short *input, short *output)
 182 {
 183     int i;
 184     int a1;
 185     short *op = output;
 186
 187     a1 = ((input[0] + 3) >> 3);
 188
 189     for (i = 0; i < 4; i++)
 190     {
 191         op[0] = a1;
 192         op[1] = a1;
 193         op[2] = a1;
 194         op[3] = a1;
 195         op += 4;
 196     }
 197 }