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4349 | Serge | 1 | /* |
2 | * This file is part of the Independent JPEG Group's software. |
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3 | * |
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4 | * The authors make NO WARRANTY or representation, either express or implied, |
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5 | * with respect to this software, its quality, accuracy, merchantability, or |
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6 | * fitness for a particular purpose. This software is provided "AS IS", and |
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7 | * you, its user, assume the entire risk as to its quality and accuracy. |
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8 | * |
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9 | * This software is copyright (C) 1994-1996, Thomas G. Lane. |
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10 | * All Rights Reserved except as specified below. |
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11 | * |
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12 | * Permission is hereby granted to use, copy, modify, and distribute this |
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13 | * software (or portions thereof) for any purpose, without fee, subject to |
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14 | * these conditions: |
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15 | * (1) If any part of the source code for this software is distributed, then |
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16 | * this README file must be included, with this copyright and no-warranty |
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17 | * notice unaltered; and any additions, deletions, or changes to the original |
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18 | * files must be clearly indicated in accompanying documentation. |
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19 | * (2) If only executable code is distributed, then the accompanying |
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20 | * documentation must state that "this software is based in part on the work |
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21 | * of the Independent JPEG Group". |
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22 | * (3) Permission for use of this software is granted only if the user accepts |
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23 | * full responsibility for any undesirable consequences; the authors accept |
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24 | * NO LIABILITY for damages of any kind. |
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25 | * |
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26 | * These conditions apply to any software derived from or based on the IJG |
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27 | * code, not just to the unmodified library. If you use our work, you ought |
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28 | * to acknowledge us. |
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29 | * |
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30 | * Permission is NOT granted for the use of any IJG author's name or company |
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31 | * name in advertising or publicity relating to this software or products |
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32 | * derived from it. This software may be referred to only as "the Independent |
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33 | * JPEG Group's software". |
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34 | * |
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35 | * We specifically permit and encourage the use of this software as the basis |
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36 | * of commercial products, provided that all warranty or liability claims are |
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37 | * assumed by the product vendor. |
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38 | * |
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39 | * This file contains a fast, not so accurate integer implementation of the |
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40 | * forward DCT (Discrete Cosine Transform). |
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41 | * |
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42 | * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT |
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43 | * on each column. Direct algorithms are also available, but they are |
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44 | * much more complex and seem not to be any faster when reduced to code. |
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45 | * |
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46 | * This implementation is based on Arai, Agui, and Nakajima's algorithm for |
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47 | * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in |
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48 | * Japanese, but the algorithm is described in the Pennebaker & Mitchell |
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49 | * JPEG textbook (see REFERENCES section in file README). The following code |
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50 | * is based directly on figure 4-8 in P&M. |
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51 | * While an 8-point DCT cannot be done in less than 11 multiplies, it is |
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52 | * possible to arrange the computation so that many of the multiplies are |
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53 | * simple scalings of the final outputs. These multiplies can then be |
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54 | * folded into the multiplications or divisions by the JPEG quantization |
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55 | * table entries. The AA&N method leaves only 5 multiplies and 29 adds |
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56 | * to be done in the DCT itself. |
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57 | * The primary disadvantage of this method is that with fixed-point math, |
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58 | * accuracy is lost due to imprecise representation of the scaled |
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59 | * quantization values. The smaller the quantization table entry, the less |
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60 | * precise the scaled value, so this implementation does worse with high- |
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61 | * quality-setting files than with low-quality ones. |
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62 | */ |
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63 | |||
64 | /** |
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65 | * @file |
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66 | * Independent JPEG Group's fast AAN dct. |
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67 | */ |
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68 | |||
69 | #include |
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70 | #include |
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71 | #include "libavutil/common.h" |
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72 | #include "dct.h" |
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73 | |||
74 | #define DCTSIZE 8 |
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75 | #define GLOBAL(x) x |
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76 | #define RIGHT_SHIFT(x, n) ((x) >> (n)) |
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77 | |||
78 | /* |
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79 | * This module is specialized to the case DCTSIZE = 8. |
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80 | */ |
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81 | |||
82 | #if DCTSIZE != 8 |
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83 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
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84 | #endif |
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85 | |||
86 | |||
87 | /* Scaling decisions are generally the same as in the LL&M algorithm; |
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88 | * see jfdctint.c for more details. However, we choose to descale |
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89 | * (right shift) multiplication products as soon as they are formed, |
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90 | * rather than carrying additional fractional bits into subsequent additions. |
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91 | * This compromises accuracy slightly, but it lets us save a few shifts. |
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92 | * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) |
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93 | * everywhere except in the multiplications proper; this saves a good deal |
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94 | * of work on 16-bit-int machines. |
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95 | * |
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96 | * Again to save a few shifts, the intermediate results between pass 1 and |
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97 | * pass 2 are not upscaled, but are represented only to integral precision. |
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98 | * |
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99 | * A final compromise is to represent the multiplicative constants to only |
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100 | * 8 fractional bits, rather than 13. This saves some shifting work on some |
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101 | * machines, and may also reduce the cost of multiplication (since there |
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102 | * are fewer one-bits in the constants). |
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103 | */ |
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104 | |||
105 | #define CONST_BITS 8 |
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106 | |||
107 | |||
108 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
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109 | * causing a lot of useless floating-point operations at run time. |
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110 | * To get around this we use the following pre-calculated constants. |
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111 | * If you change CONST_BITS you may want to add appropriate values. |
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112 | * (With a reasonable C compiler, you can just rely on the FIX() macro...) |
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113 | */ |
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114 | |||
115 | #if CONST_BITS == 8 |
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116 | #define FIX_0_382683433 ((int32_t) 98) /* FIX(0.382683433) */ |
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117 | #define FIX_0_541196100 ((int32_t) 139) /* FIX(0.541196100) */ |
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118 | #define FIX_0_707106781 ((int32_t) 181) /* FIX(0.707106781) */ |
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119 | #define FIX_1_306562965 ((int32_t) 334) /* FIX(1.306562965) */ |
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120 | #else |
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121 | #define FIX_0_382683433 FIX(0.382683433) |
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122 | #define FIX_0_541196100 FIX(0.541196100) |
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123 | #define FIX_0_707106781 FIX(0.707106781) |
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124 | #define FIX_1_306562965 FIX(1.306562965) |
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125 | #endif |
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126 | |||
127 | |||
128 | /* We can gain a little more speed, with a further compromise in accuracy, |
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129 | * by omitting the addition in a descaling shift. This yields an incorrectly |
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130 | * rounded result half the time... |
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131 | */ |
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132 | |||
133 | #ifndef USE_ACCURATE_ROUNDING |
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134 | #undef DESCALE |
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135 | #define DESCALE(x,n) RIGHT_SHIFT(x, n) |
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136 | #endif |
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137 | |||
138 | |||
139 | /* Multiply a int16_t variable by an int32_t constant, and immediately |
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140 | * descale to yield a int16_t result. |
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141 | */ |
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142 | |||
143 | #define MULTIPLY(var,const) ((int16_t) DESCALE((var) * (const), CONST_BITS)) |
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144 | |||
145 | static av_always_inline void row_fdct(int16_t * data){ |
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146 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
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147 | int tmp10, tmp11, tmp12, tmp13; |
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148 | int z1, z2, z3, z4, z5, z11, z13; |
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149 | int16_t *dataptr; |
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150 | int ctr; |
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151 | |||
152 | /* Pass 1: process rows. */ |
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153 | |||
154 | dataptr = data; |
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155 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
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156 | tmp0 = dataptr[0] + dataptr[7]; |
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157 | tmp7 = dataptr[0] - dataptr[7]; |
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158 | tmp1 = dataptr[1] + dataptr[6]; |
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159 | tmp6 = dataptr[1] - dataptr[6]; |
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160 | tmp2 = dataptr[2] + dataptr[5]; |
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161 | tmp5 = dataptr[2] - dataptr[5]; |
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162 | tmp3 = dataptr[3] + dataptr[4]; |
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163 | tmp4 = dataptr[3] - dataptr[4]; |
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164 | |||
165 | /* Even part */ |
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166 | |||
167 | tmp10 = tmp0 + tmp3; /* phase 2 */ |
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168 | tmp13 = tmp0 - tmp3; |
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169 | tmp11 = tmp1 + tmp2; |
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170 | tmp12 = tmp1 - tmp2; |
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171 | |||
172 | dataptr[0] = tmp10 + tmp11; /* phase 3 */ |
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173 | dataptr[4] = tmp10 - tmp11; |
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174 | |||
175 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
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176 | dataptr[2] = tmp13 + z1; /* phase 5 */ |
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177 | dataptr[6] = tmp13 - z1; |
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178 | |||
179 | /* Odd part */ |
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180 | |||
181 | tmp10 = tmp4 + tmp5; /* phase 2 */ |
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182 | tmp11 = tmp5 + tmp6; |
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183 | tmp12 = tmp6 + tmp7; |
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184 | |||
185 | /* The rotator is modified from fig 4-8 to avoid extra negations. */ |
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186 | z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
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187 | z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
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188 | z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
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189 | z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
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190 | |||
191 | z11 = tmp7 + z3; /* phase 5 */ |
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192 | z13 = tmp7 - z3; |
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193 | |||
194 | dataptr[5] = z13 + z2; /* phase 6 */ |
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195 | dataptr[3] = z13 - z2; |
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196 | dataptr[1] = z11 + z4; |
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197 | dataptr[7] = z11 - z4; |
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198 | |||
199 | dataptr += DCTSIZE; /* advance pointer to next row */ |
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200 | } |
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201 | } |
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202 | |||
203 | /* |
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204 | * Perform the forward DCT on one block of samples. |
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205 | */ |
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206 | |||
207 | GLOBAL(void) |
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208 | ff_fdct_ifast (int16_t * data) |
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209 | { |
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210 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
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211 | int tmp10, tmp11, tmp12, tmp13; |
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212 | int z1, z2, z3, z4, z5, z11, z13; |
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213 | int16_t *dataptr; |
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214 | int ctr; |
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215 | |||
216 | row_fdct(data); |
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217 | |||
218 | /* Pass 2: process columns. */ |
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219 | |||
220 | dataptr = data; |
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221 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
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222 | tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7]; |
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223 | tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7]; |
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224 | tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6]; |
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225 | tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6]; |
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226 | tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5]; |
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227 | tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5]; |
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228 | tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4]; |
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229 | tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4]; |
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230 | |||
231 | /* Even part */ |
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232 | |||
233 | tmp10 = tmp0 + tmp3; /* phase 2 */ |
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234 | tmp13 = tmp0 - tmp3; |
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235 | tmp11 = tmp1 + tmp2; |
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236 | tmp12 = tmp1 - tmp2; |
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237 | |||
238 | dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */ |
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239 | dataptr[DCTSIZE*4] = tmp10 - tmp11; |
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240 | |||
241 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
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242 | dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */ |
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243 | dataptr[DCTSIZE*6] = tmp13 - z1; |
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244 | |||
245 | /* Odd part */ |
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246 | |||
247 | tmp10 = tmp4 + tmp5; /* phase 2 */ |
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248 | tmp11 = tmp5 + tmp6; |
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249 | tmp12 = tmp6 + tmp7; |
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250 | |||
251 | /* The rotator is modified from fig 4-8 to avoid extra negations. */ |
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252 | z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
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253 | z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
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254 | z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
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255 | z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
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256 | |||
257 | z11 = tmp7 + z3; /* phase 5 */ |
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258 | z13 = tmp7 - z3; |
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259 | |||
260 | dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */ |
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261 | dataptr[DCTSIZE*3] = z13 - z2; |
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262 | dataptr[DCTSIZE*1] = z11 + z4; |
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263 | dataptr[DCTSIZE*7] = z11 - z4; |
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264 | |||
265 | dataptr++; /* advance pointer to next column */ |
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266 | } |
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267 | } |
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268 | |||
269 | /* |
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270 | * Perform the forward 2-4-8 DCT on one block of samples. |
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271 | */ |
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272 | |||
273 | GLOBAL(void) |
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274 | ff_fdct_ifast248 (int16_t * data) |
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275 | { |
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276 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
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277 | int tmp10, tmp11, tmp12, tmp13; |
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278 | int z1; |
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279 | int16_t *dataptr; |
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280 | int ctr; |
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281 | |||
282 | row_fdct(data); |
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283 | |||
284 | /* Pass 2: process columns. */ |
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285 | |||
286 | dataptr = data; |
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287 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
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288 | tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1]; |
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289 | tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3]; |
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290 | tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5]; |
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291 | tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7]; |
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292 | tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1]; |
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293 | tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3]; |
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294 | tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5]; |
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295 | tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7]; |
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296 | |||
297 | /* Even part */ |
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298 | |||
299 | tmp10 = tmp0 + tmp3; |
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300 | tmp11 = tmp1 + tmp2; |
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301 | tmp12 = tmp1 - tmp2; |
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302 | tmp13 = tmp0 - tmp3; |
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303 | |||
304 | dataptr[DCTSIZE*0] = tmp10 + tmp11; |
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305 | dataptr[DCTSIZE*4] = tmp10 - tmp11; |
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306 | |||
307 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
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308 | dataptr[DCTSIZE*2] = tmp13 + z1; |
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309 | dataptr[DCTSIZE*6] = tmp13 - z1; |
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310 | |||
311 | tmp10 = tmp4 + tmp7; |
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312 | tmp11 = tmp5 + tmp6; |
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313 | tmp12 = tmp5 - tmp6; |
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314 | tmp13 = tmp4 - tmp7; |
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315 | |||
316 | dataptr[DCTSIZE*1] = tmp10 + tmp11; |
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317 | dataptr[DCTSIZE*5] = tmp10 - tmp11; |
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318 | |||
319 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
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320 | dataptr[DCTSIZE*3] = tmp13 + z1; |
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321 | dataptr[DCTSIZE*7] = tmp13 - z1; |
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322 | |||
323 | dataptr++; /* advance pointer to next column */ |
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324 | } |
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325 | } |
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326 | |||
327 | |||
328 | #undef GLOBAL |
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329 | #undef CONST_BITS |
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330 | #undef DESCALE |
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331 | #undef FIX_0_541196100 |
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332 | #undef FIX_1_306562965 |