| 1 | /*
|
|---|
| 2 | * jidctint.c
|
|---|
| 3 | *
|
|---|
| 4 | * Copyright (C) 1991-1998, Thomas G. Lane.
|
|---|
| 5 | * This file is part of the Independent JPEG Group's software.
|
|---|
| 6 | * For conditions of distribution and use, see the accompanying README file.
|
|---|
| 7 | *
|
|---|
| 8 | * This file contains a slow-but-accurate integer implementation of the
|
|---|
| 9 | * inverse DCT (Discrete Cosine Transform). In the IJG code, this routine
|
|---|
| 10 | * must also perform dequantization of the input coefficients.
|
|---|
| 11 | *
|
|---|
| 12 | * A 2-D IDCT can be done by 1-D IDCT on each column followed by 1-D IDCT
|
|---|
| 13 | * on each row (or vice versa, but it's more convenient to emit a row at
|
|---|
| 14 | * a time). Direct algorithms are also available, but they are much more
|
|---|
| 15 | * complex and seem not to be any faster when reduced to code.
|
|---|
| 16 | *
|
|---|
| 17 | * This implementation is based on an algorithm described in
|
|---|
| 18 | * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
|
|---|
| 19 | * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
|
|---|
| 20 | * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
|
|---|
| 21 | * The primary algorithm described there uses 11 multiplies and 29 adds.
|
|---|
| 22 | * We use their alternate method with 12 multiplies and 32 adds.
|
|---|
| 23 | * The advantage of this method is that no data path contains more than one
|
|---|
| 24 | * multiplication; this allows a very simple and accurate implementation in
|
|---|
| 25 | * scaled fixed-point arithmetic, with a minimal number of shifts.
|
|---|
| 26 | */
|
|---|
| 27 |
|
|---|
| 28 | #define JPEG_INTERNALS
|
|---|
| 29 | #include "jinclude.h"
|
|---|
| 30 | #include "jpeglib.h"
|
|---|
| 31 | #include "jdct.h" /* Private declarations for DCT subsystem */
|
|---|
| 32 |
|
|---|
| 33 | #ifdef DCT_ISLOW_SUPPORTED
|
|---|
| 34 |
|
|---|
| 35 |
|
|---|
| 36 | /*
|
|---|
| 37 | * This module is specialized to the case DCTSIZE = 8.
|
|---|
| 38 | */
|
|---|
| 39 |
|
|---|
| 40 | #if DCTSIZE != 8
|
|---|
| 41 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
|
|---|
| 42 | #endif
|
|---|
| 43 |
|
|---|
| 44 |
|
|---|
| 45 | /*
|
|---|
| 46 | * The poop on this scaling stuff is as follows:
|
|---|
| 47 | *
|
|---|
| 48 | * Each 1-D IDCT step produces outputs which are a factor of sqrt(N)
|
|---|
| 49 | * larger than the true IDCT outputs. The final outputs are therefore
|
|---|
| 50 | * a factor of N larger than desired; since N=8 this can be cured by
|
|---|
| 51 | * a simple right shift at the end of the algorithm. The advantage of
|
|---|
| 52 | * this arrangement is that we save two multiplications per 1-D IDCT,
|
|---|
| 53 | * because the y0 and y4 inputs need not be divided by sqrt(N).
|
|---|
| 54 | *
|
|---|
| 55 | * We have to do addition and subtraction of the integer inputs, which
|
|---|
| 56 | * is no problem, and multiplication by fractional constants, which is
|
|---|
| 57 | * a problem to do in integer arithmetic. We multiply all the constants
|
|---|
| 58 | * by CONST_SCALE and convert them to integer constants (thus retaining
|
|---|
| 59 | * CONST_BITS bits of precision in the constants). After doing a
|
|---|
| 60 | * multiplication we have to divide the product by CONST_SCALE, with proper
|
|---|
| 61 | * rounding, to produce the correct output. This division can be done
|
|---|
| 62 | * cheaply as a right shift of CONST_BITS bits. We postpone shifting
|
|---|
| 63 | * as long as possible so that partial sums can be added together with
|
|---|
| 64 | * full fractional precision.
|
|---|
| 65 | *
|
|---|
| 66 | * The outputs of the first pass are scaled up by PASS1_BITS bits so that
|
|---|
| 67 | * they are represented to better-than-integral precision. These outputs
|
|---|
| 68 | * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
|
|---|
| 69 | * with the recommended scaling. (To scale up 12-bit sample data further, an
|
|---|
| 70 | * intermediate INT32 array would be needed.)
|
|---|
| 71 | *
|
|---|
| 72 | * To avoid overflow of the 32-bit intermediate results in pass 2, we must
|
|---|
| 73 | * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis
|
|---|
| 74 | * shows that the values given below are the most effective.
|
|---|
| 75 | */
|
|---|
| 76 |
|
|---|
| 77 | #if BITS_IN_JSAMPLE == 8
|
|---|
| 78 | #define CONST_BITS 13
|
|---|
| 79 | #define PASS1_BITS 2
|
|---|
| 80 | #else
|
|---|
| 81 | #define CONST_BITS 13
|
|---|
| 82 | #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
|
|---|
| 83 | #endif
|
|---|
| 84 |
|
|---|
| 85 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
|
|---|
| 86 | * causing a lot of useless floating-point operations at run time.
|
|---|
| 87 | * To get around this we use the following pre-calculated constants.
|
|---|
| 88 | * If you change CONST_BITS you may want to add appropriate values.
|
|---|
| 89 | * (With a reasonable C compiler, you can just rely on the FIX() macro...)
|
|---|
| 90 | */
|
|---|
| 91 |
|
|---|
| 92 | #if CONST_BITS == 13
|
|---|
| 93 | #define FIX_0_298631336 ((INT32) 2446) /* FIX(0.298631336) */
|
|---|
| 94 | #define FIX_0_390180644 ((INT32) 3196) /* FIX(0.390180644) */
|
|---|
| 95 | #define FIX_0_541196100 ((INT32) 4433) /* FIX(0.541196100) */
|
|---|
| 96 | #define FIX_0_765366865 ((INT32) 6270) /* FIX(0.765366865) */
|
|---|
| 97 | #define FIX_0_899976223 ((INT32) 7373) /* FIX(0.899976223) */
|
|---|
| 98 | #define FIX_1_175875602 ((INT32) 9633) /* FIX(1.175875602) */
|
|---|
| 99 | #define FIX_1_501321110 ((INT32) 12299) /* FIX(1.501321110) */
|
|---|
| 100 | #define FIX_1_847759065 ((INT32) 15137) /* FIX(1.847759065) */
|
|---|
| 101 | #define FIX_1_961570560 ((INT32) 16069) /* FIX(1.961570560) */
|
|---|
| 102 | #define FIX_2_053119869 ((INT32) 16819) /* FIX(2.053119869) */
|
|---|
| 103 | #define FIX_2_562915447 ((INT32) 20995) /* FIX(2.562915447) */
|
|---|
| 104 | #define FIX_3_072711026 ((INT32) 25172) /* FIX(3.072711026) */
|
|---|
| 105 | #else
|
|---|
| 106 | #define FIX_0_298631336 FIX(0.298631336)
|
|---|
| 107 | #define FIX_0_390180644 FIX(0.390180644)
|
|---|
| 108 | #define FIX_0_541196100 FIX(0.541196100)
|
|---|
| 109 | #define FIX_0_765366865 FIX(0.765366865)
|
|---|
| 110 | #define FIX_0_899976223 FIX(0.899976223)
|
|---|
| 111 | #define FIX_1_175875602 FIX(1.175875602)
|
|---|
| 112 | #define FIX_1_501321110 FIX(1.501321110)
|
|---|
| 113 | #define FIX_1_847759065 FIX(1.847759065)
|
|---|
| 114 | #define FIX_1_961570560 FIX(1.961570560)
|
|---|
| 115 | #define FIX_2_053119869 FIX(2.053119869)
|
|---|
| 116 | #define FIX_2_562915447 FIX(2.562915447)
|
|---|
| 117 | #define FIX_3_072711026 FIX(3.072711026)
|
|---|
| 118 | #endif
|
|---|
| 119 |
|
|---|
| 120 |
|
|---|
| 121 | /* Multiply an INT32 variable by an INT32 constant to yield an INT32 result.
|
|---|
| 122 | * For 8-bit samples with the recommended scaling, all the variable
|
|---|
| 123 | * and constant values involved are no more than 16 bits wide, so a
|
|---|
| 124 | * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
|
|---|
| 125 | * For 12-bit samples, a full 32-bit multiplication will be needed.
|
|---|
| 126 | */
|
|---|
| 127 |
|
|---|
| 128 | #if BITS_IN_JSAMPLE == 8
|
|---|
| 129 | #define MULTIPLY(var,const) MULTIPLY16C16(var,const)
|
|---|
| 130 | #else
|
|---|
| 131 | #define MULTIPLY(var,const) ((var) * (const))
|
|---|
| 132 | #endif
|
|---|
| 133 |
|
|---|
| 134 |
|
|---|
| 135 | /* Dequantize a coefficient by multiplying it by the multiplier-table
|
|---|
| 136 | * entry; produce an int result. In this module, both inputs and result
|
|---|
| 137 | * are 16 bits or less, so either int or short multiply will work.
|
|---|
| 138 | */
|
|---|
| 139 |
|
|---|
| 140 | #define DEQUANTIZE(coef,quantval) (((ISLOW_MULT_TYPE) (coef)) * (quantval))
|
|---|
| 141 |
|
|---|
| 142 |
|
|---|
| 143 | /*
|
|---|
| 144 | * Perform dequantization and inverse DCT on one block of coefficients.
|
|---|
| 145 | */
|
|---|
| 146 |
|
|---|
| 147 | GLOBAL(void)
|
|---|
| 148 | jpeg_idct_islow (j_decompress_ptr cinfo, jpeg_component_info * compptr,
|
|---|
| 149 | JCOEFPTR coef_block,
|
|---|
| 150 | JSAMPARRAY output_buf, JDIMENSION output_col)
|
|---|
| 151 | {
|
|---|
| 152 | INT32 tmp0, tmp1, tmp2, tmp3;
|
|---|
| 153 | INT32 tmp10, tmp11, tmp12, tmp13;
|
|---|
| 154 | INT32 z1, z2, z3, z4, z5;
|
|---|
| 155 | JCOEFPTR inptr;
|
|---|
| 156 | ISLOW_MULT_TYPE * quantptr;
|
|---|
| 157 | int * wsptr;
|
|---|
| 158 | JSAMPROW outptr;
|
|---|
| 159 | JSAMPLE *range_limit = IDCT_range_limit(cinfo);
|
|---|
| 160 | int ctr;
|
|---|
| 161 | int workspace[DCTSIZE2]; /* buffers data between passes */
|
|---|
| 162 | SHIFT_TEMPS
|
|---|
| 163 |
|
|---|
| 164 | /* Pass 1: process columns from input, store into work array. */
|
|---|
| 165 | /* Note results are scaled up by sqrt(8) compared to a true IDCT; */
|
|---|
| 166 | /* furthermore, we scale the results by 2**PASS1_BITS. */
|
|---|
| 167 |
|
|---|
| 168 | inptr = coef_block;
|
|---|
| 169 | quantptr = (ISLOW_MULT_TYPE *) compptr->dct_table;
|
|---|
| 170 | wsptr = workspace;
|
|---|
| 171 | for (ctr = DCTSIZE; ctr > 0; ctr--) {
|
|---|
| 172 | /* Due to quantization, we will usually find that many of the input
|
|---|
| 173 | * coefficients are zero, especially the AC terms. We can exploit this
|
|---|
| 174 | * by short-circuiting the IDCT calculation for any column in which all
|
|---|
| 175 | * the AC terms are zero. In that case each output is equal to the
|
|---|
| 176 | * DC coefficient (with scale factor as needed).
|
|---|
| 177 | * With typical images and quantization tables, half or more of the
|
|---|
| 178 | * column DCT calculations can be simplified this way.
|
|---|
| 179 | */
|
|---|
| 180 |
|
|---|
| 181 | if (inptr[DCTSIZE*1] == 0 && inptr[DCTSIZE*2] == 0 &&
|
|---|
| 182 | inptr[DCTSIZE*3] == 0 && inptr[DCTSIZE*4] == 0 &&
|
|---|
| 183 | inptr[DCTSIZE*5] == 0 && inptr[DCTSIZE*6] == 0 &&
|
|---|
| 184 | inptr[DCTSIZE*7] == 0) {
|
|---|
| 185 | /* AC terms all zero */
|
|---|
| 186 | int dcval = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]) << PASS1_BITS;
|
|---|
| 187 |
|
|---|
| 188 | wsptr[DCTSIZE*0] = dcval;
|
|---|
| 189 | wsptr[DCTSIZE*1] = dcval;
|
|---|
| 190 | wsptr[DCTSIZE*2] = dcval;
|
|---|
| 191 | wsptr[DCTSIZE*3] = dcval;
|
|---|
| 192 | wsptr[DCTSIZE*4] = dcval;
|
|---|
| 193 | wsptr[DCTSIZE*5] = dcval;
|
|---|
| 194 | wsptr[DCTSIZE*6] = dcval;
|
|---|
| 195 | wsptr[DCTSIZE*7] = dcval;
|
|---|
| 196 |
|
|---|
| 197 | inptr++; /* advance pointers to next column */
|
|---|
| 198 | quantptr++;
|
|---|
| 199 | wsptr++;
|
|---|
| 200 | continue;
|
|---|
| 201 | }
|
|---|
| 202 |
|
|---|
| 203 | /* Even part: reverse the even part of the forward DCT. */
|
|---|
| 204 | /* The rotator is sqrt(2)*c(-6). */
|
|---|
| 205 |
|
|---|
| 206 | z2 = DEQUANTIZE(inptr[DCTSIZE*2], quantptr[DCTSIZE*2]);
|
|---|
| 207 | z3 = DEQUANTIZE(inptr[DCTSIZE*6], quantptr[DCTSIZE*6]);
|
|---|
| 208 |
|
|---|
| 209 | z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
|
|---|
| 210 | tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
|
|---|
| 211 | tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
|
|---|
| 212 |
|
|---|
| 213 | z2 = DEQUANTIZE(inptr[DCTSIZE*0], quantptr[DCTSIZE*0]);
|
|---|
| 214 | z3 = DEQUANTIZE(inptr[DCTSIZE*4], quantptr[DCTSIZE*4]);
|
|---|
| 215 |
|
|---|
| 216 | tmp0 = (z2 + z3) << CONST_BITS;
|
|---|
| 217 | tmp1 = (z2 - z3) << CONST_BITS;
|
|---|
| 218 |
|
|---|
| 219 | tmp10 = tmp0 + tmp3;
|
|---|
| 220 | tmp13 = tmp0 - tmp3;
|
|---|
| 221 | tmp11 = tmp1 + tmp2;
|
|---|
| 222 | tmp12 = tmp1 - tmp2;
|
|---|
| 223 |
|
|---|
| 224 | /* Odd part per figure 8; the matrix is unitary and hence its
|
|---|
| 225 | * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
|
|---|
| 226 | */
|
|---|
| 227 |
|
|---|
| 228 | tmp0 = DEQUANTIZE(inptr[DCTSIZE*7], quantptr[DCTSIZE*7]);
|
|---|
| 229 | tmp1 = DEQUANTIZE(inptr[DCTSIZE*5], quantptr[DCTSIZE*5]);
|
|---|
| 230 | tmp2 = DEQUANTIZE(inptr[DCTSIZE*3], quantptr[DCTSIZE*3]);
|
|---|
| 231 | tmp3 = DEQUANTIZE(inptr[DCTSIZE*1], quantptr[DCTSIZE*1]);
|
|---|
| 232 |
|
|---|
| 233 | z1 = tmp0 + tmp3;
|
|---|
| 234 | z2 = tmp1 + tmp2;
|
|---|
| 235 | z3 = tmp0 + tmp2;
|
|---|
| 236 | z4 = tmp1 + tmp3;
|
|---|
| 237 | z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
|
|---|
| 238 |
|
|---|
| 239 | tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
|
|---|
| 240 | tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
|
|---|
| 241 | tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
|
|---|
| 242 | tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
|
|---|
| 243 | z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
|
|---|
| 244 | z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
|
|---|
| 245 | z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
|
|---|
| 246 | z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
|
|---|
| 247 |
|
|---|
| 248 | z3 += z5;
|
|---|
| 249 | z4 += z5;
|
|---|
| 250 |
|
|---|
| 251 | tmp0 += z1 + z3;
|
|---|
| 252 | tmp1 += z2 + z4;
|
|---|
| 253 | tmp2 += z2 + z3;
|
|---|
| 254 | tmp3 += z1 + z4;
|
|---|
| 255 |
|
|---|
| 256 | /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
|
|---|
| 257 |
|
|---|
| 258 | wsptr[DCTSIZE*0] = (int) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS);
|
|---|
| 259 | wsptr[DCTSIZE*7] = (int) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS);
|
|---|
| 260 | wsptr[DCTSIZE*1] = (int) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS);
|
|---|
| 261 | wsptr[DCTSIZE*6] = (int) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS);
|
|---|
| 262 | wsptr[DCTSIZE*2] = (int) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS);
|
|---|
| 263 | wsptr[DCTSIZE*5] = (int) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS);
|
|---|
| 264 | wsptr[DCTSIZE*3] = (int) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS);
|
|---|
| 265 | wsptr[DCTSIZE*4] = (int) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS);
|
|---|
| 266 |
|
|---|
| 267 | inptr++; /* advance pointers to next column */
|
|---|
| 268 | quantptr++;
|
|---|
| 269 | wsptr++;
|
|---|
| 270 | }
|
|---|
| 271 |
|
|---|
| 272 | /* Pass 2: process rows from work array, store into output array. */
|
|---|
| 273 | /* Note that we must descale the results by a factor of 8 == 2**3, */
|
|---|
| 274 | /* and also undo the PASS1_BITS scaling. */
|
|---|
| 275 |
|
|---|
| 276 | wsptr = workspace;
|
|---|
| 277 | for (ctr = 0; ctr < DCTSIZE; ctr++) {
|
|---|
| 278 | outptr = output_buf[ctr] + output_col;
|
|---|
| 279 | /* Rows of zeroes can be exploited in the same way as we did with columns.
|
|---|
| 280 | * However, the column calculation has created many nonzero AC terms, so
|
|---|
| 281 | * the simplification applies less often (typically 5% to 10% of the time).
|
|---|
| 282 | * On machines with very fast multiplication, it's possible that the
|
|---|
| 283 | * test takes more time than it's worth. In that case this section
|
|---|
| 284 | * may be commented out.
|
|---|
| 285 | */
|
|---|
| 286 |
|
|---|
| 287 | #ifndef NO_ZERO_ROW_TEST
|
|---|
| 288 | if (wsptr[1] == 0 && wsptr[2] == 0 && wsptr[3] == 0 && wsptr[4] == 0 &&
|
|---|
| 289 | wsptr[5] == 0 && wsptr[6] == 0 && wsptr[7] == 0) {
|
|---|
| 290 | /* AC terms all zero */
|
|---|
| 291 | JSAMPLE dcval = range_limit[(int) DESCALE((INT32) wsptr[0], PASS1_BITS+3)
|
|---|
| 292 | & RANGE_MASK];
|
|---|
| 293 |
|
|---|
| 294 | outptr[0] = dcval;
|
|---|
| 295 | outptr[1] = dcval;
|
|---|
| 296 | outptr[2] = dcval;
|
|---|
| 297 | outptr[3] = dcval;
|
|---|
| 298 | outptr[4] = dcval;
|
|---|
| 299 | outptr[5] = dcval;
|
|---|
| 300 | outptr[6] = dcval;
|
|---|
| 301 | outptr[7] = dcval;
|
|---|
| 302 |
|
|---|
| 303 | wsptr += DCTSIZE; /* advance pointer to next row */
|
|---|
| 304 | continue;
|
|---|
| 305 | }
|
|---|
| 306 | #endif
|
|---|
| 307 |
|
|---|
| 308 | /* Even part: reverse the even part of the forward DCT. */
|
|---|
| 309 | /* The rotator is sqrt(2)*c(-6). */
|
|---|
| 310 |
|
|---|
| 311 | z2 = (INT32) wsptr[2];
|
|---|
| 312 | z3 = (INT32) wsptr[6];
|
|---|
| 313 |
|
|---|
| 314 | z1 = MULTIPLY(z2 + z3, FIX_0_541196100);
|
|---|
| 315 | tmp2 = z1 + MULTIPLY(z3, - FIX_1_847759065);
|
|---|
| 316 | tmp3 = z1 + MULTIPLY(z2, FIX_0_765366865);
|
|---|
| 317 |
|
|---|
| 318 | tmp0 = ((INT32) wsptr[0] + (INT32) wsptr[4]) << CONST_BITS;
|
|---|
| 319 | tmp1 = ((INT32) wsptr[0] - (INT32) wsptr[4]) << CONST_BITS;
|
|---|
| 320 |
|
|---|
| 321 | tmp10 = tmp0 + tmp3;
|
|---|
| 322 | tmp13 = tmp0 - tmp3;
|
|---|
| 323 | tmp11 = tmp1 + tmp2;
|
|---|
| 324 | tmp12 = tmp1 - tmp2;
|
|---|
| 325 |
|
|---|
| 326 | /* Odd part per figure 8; the matrix is unitary and hence its
|
|---|
| 327 | * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
|
|---|
| 328 | */
|
|---|
| 329 |
|
|---|
| 330 | tmp0 = (INT32) wsptr[7];
|
|---|
| 331 | tmp1 = (INT32) wsptr[5];
|
|---|
| 332 | tmp2 = (INT32) wsptr[3];
|
|---|
| 333 | tmp3 = (INT32) wsptr[1];
|
|---|
| 334 |
|
|---|
| 335 | z1 = tmp0 + tmp3;
|
|---|
| 336 | z2 = tmp1 + tmp2;
|
|---|
| 337 | z3 = tmp0 + tmp2;
|
|---|
| 338 | z4 = tmp1 + tmp3;
|
|---|
| 339 | z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
|
|---|
| 340 |
|
|---|
| 341 | tmp0 = MULTIPLY(tmp0, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
|
|---|
| 342 | tmp1 = MULTIPLY(tmp1, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
|
|---|
| 343 | tmp2 = MULTIPLY(tmp2, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
|
|---|
| 344 | tmp3 = MULTIPLY(tmp3, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
|
|---|
| 345 | z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
|
|---|
| 346 | z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
|
|---|
| 347 | z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
|
|---|
| 348 | z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
|
|---|
| 349 |
|
|---|
| 350 | z3 += z5;
|
|---|
| 351 | z4 += z5;
|
|---|
| 352 |
|
|---|
| 353 | tmp0 += z1 + z3;
|
|---|
| 354 | tmp1 += z2 + z4;
|
|---|
| 355 | tmp2 += z2 + z3;
|
|---|
| 356 | tmp3 += z1 + z4;
|
|---|
| 357 |
|
|---|
| 358 | /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
|
|---|
| 359 |
|
|---|
| 360 | outptr[0] = range_limit[(int) DESCALE(tmp10 + tmp3,
|
|---|
| 361 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 362 | & RANGE_MASK];
|
|---|
| 363 | outptr[7] = range_limit[(int) DESCALE(tmp10 - tmp3,
|
|---|
| 364 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 365 | & RANGE_MASK];
|
|---|
| 366 | outptr[1] = range_limit[(int) DESCALE(tmp11 + tmp2,
|
|---|
| 367 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 368 | & RANGE_MASK];
|
|---|
| 369 | outptr[6] = range_limit[(int) DESCALE(tmp11 - tmp2,
|
|---|
| 370 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 371 | & RANGE_MASK];
|
|---|
| 372 | outptr[2] = range_limit[(int) DESCALE(tmp12 + tmp1,
|
|---|
| 373 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 374 | & RANGE_MASK];
|
|---|
| 375 | outptr[5] = range_limit[(int) DESCALE(tmp12 - tmp1,
|
|---|
| 376 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 377 | & RANGE_MASK];
|
|---|
| 378 | outptr[3] = range_limit[(int) DESCALE(tmp13 + tmp0,
|
|---|
| 379 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 380 | & RANGE_MASK];
|
|---|
| 381 | outptr[4] = range_limit[(int) DESCALE(tmp13 - tmp0,
|
|---|
| 382 | CONST_BITS+PASS1_BITS+3)
|
|---|
| 383 | & RANGE_MASK];
|
|---|
| 384 |
|
|---|
| 385 | wsptr += DCTSIZE; /* advance pointer to next row */
|
|---|
| 386 | }
|
|---|
| 387 | }
|
|---|
| 388 |
|
|---|
| 389 | #endif /* DCT_ISLOW_SUPPORTED */
|
|---|
