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jrevdct.c
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1 /*
2  * This file is part of the Independent JPEG Group's software.
3  *
4  * The authors make NO WARRANTY or representation, either express or implied,
5  * with respect to this software, its quality, accuracy, merchantability, or
6  * fitness for a particular purpose. This software is provided "AS IS", and
7  * you, its user, assume the entire risk as to its quality and accuracy.
8  *
9  * This software is copyright (C) 1991, 1992, Thomas G. Lane.
10  * All Rights Reserved except as specified below.
11  *
12  * Permission is hereby granted to use, copy, modify, and distribute this
13  * software (or portions thereof) for any purpose, without fee, subject to
14  * these conditions:
15  * (1) If any part of the source code for this software is distributed, then
16  * this README file must be included, with this copyright and no-warranty
17  * notice unaltered; and any additions, deletions, or changes to the original
18  * files must be clearly indicated in accompanying documentation.
19  * (2) If only executable code is distributed, then the accompanying
20  * documentation must state that "this software is based in part on the work
21  * of the Independent JPEG Group".
22  * (3) Permission for use of this software is granted only if the user accepts
23  * full responsibility for any undesirable consequences; the authors accept
24  * NO LIABILITY for damages of any kind.
25  *
26  * These conditions apply to any software derived from or based on the IJG
27  * code, not just to the unmodified library. If you use our work, you ought
28  * to acknowledge us.
29  *
30  * Permission is NOT granted for the use of any IJG author's name or company
31  * name in advertising or publicity relating to this software or products
32  * derived from it. This software may be referred to only as "the Independent
33  * JPEG Group's software".
34  *
35  * We specifically permit and encourage the use of this software as the basis
36  * of commercial products, provided that all warranty or liability claims are
37  * assumed by the product vendor.
38  *
39  * This file contains the basic inverse-DCT transformation subroutine.
40  *
41  * This implementation is based on an algorithm described in
42  * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
43  * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
44  * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
45  * The primary algorithm described there uses 11 multiplies and 29 adds.
46  * We use their alternate method with 12 multiplies and 32 adds.
47  * The advantage of this method is that no data path contains more than one
48  * multiplication; this allows a very simple and accurate implementation in
49  * scaled fixed-point arithmetic, with a minimal number of shifts.
50  *
51  * I've made lots of modifications to attempt to take advantage of the
52  * sparse nature of the DCT matrices we're getting. Although the logic
53  * is cumbersome, it's straightforward and the resulting code is much
54  * faster.
55  *
56  * A better way to do this would be to pass in the DCT block as a sparse
57  * matrix, perhaps with the difference cases encoded.
58  */
59 
60 /**
61  * @file
62  * Independent JPEG Group's LLM idct.
63  */
64 
65 #include "libavutil/common.h"
66 #include "dct.h"
67 
68 #define EIGHT_BIT_SAMPLES
69 
70 #define DCTSIZE 8
71 #define DCTSIZE2 64
72 
73 #define GLOBAL
74 
75 #define RIGHT_SHIFT(x, n) ((x) >> (n))
76 
77 typedef int16_t DCTBLOCK[DCTSIZE2];
78 
79 #define CONST_BITS 13
80 
81 /*
82  * This routine is specialized to the case DCTSIZE = 8.
83  */
84 
85 #if DCTSIZE != 8
86  Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */
87 #endif
88 
89 
90 /*
91  * A 2-D IDCT can be done by 1-D IDCT on each row followed by 1-D IDCT
92  * on each column. Direct algorithms are also available, but they are
93  * much more complex and seem not to be any faster when reduced to code.
94  *
95  * The poop on this scaling stuff is as follows:
96  *
97  * Each 1-D IDCT step produces outputs which are a factor of sqrt(N)
98  * larger than the true IDCT outputs. The final outputs are therefore
99  * a factor of N larger than desired; since N=8 this can be cured by
100  * a simple right shift at the end of the algorithm. The advantage of
101  * this arrangement is that we save two multiplications per 1-D IDCT,
102  * because the y0 and y4 inputs need not be divided by sqrt(N).
103  *
104  * We have to do addition and subtraction of the integer inputs, which
105  * is no problem, and multiplication by fractional constants, which is
106  * a problem to do in integer arithmetic. We multiply all the constants
107  * by CONST_SCALE and convert them to integer constants (thus retaining
108  * CONST_BITS bits of precision in the constants). After doing a
109  * multiplication we have to divide the product by CONST_SCALE, with proper
110  * rounding, to produce the correct output. This division can be done
111  * cheaply as a right shift of CONST_BITS bits. We postpone shifting
112  * as long as possible so that partial sums can be added together with
113  * full fractional precision.
114  *
115  * The outputs of the first pass are scaled up by PASS1_BITS bits so that
116  * they are represented to better-than-integral precision. These outputs
117  * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
118  * with the recommended scaling. (To scale up 12-bit sample data further, an
119  * intermediate int32 array would be needed.)
120  *
121  * To avoid overflow of the 32-bit intermediate results in pass 2, we must
122  * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis
123  * shows that the values given below are the most effective.
124  */
125 
126 #ifdef EIGHT_BIT_SAMPLES
127 #define PASS1_BITS 2
128 #else
129 #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
130 #endif
131 
132 #define ONE ((int32_t) 1)
133 
134 #define CONST_SCALE (ONE << CONST_BITS)
135 
136 /* Convert a positive real constant to an integer scaled by CONST_SCALE.
137  * IMPORTANT: if your compiler doesn't do this arithmetic at compile time,
138  * you will pay a significant penalty in run time. In that case, figure
139  * the correct integer constant values and insert them by hand.
140  */
141 
142 /* Actually FIX is no longer used, we precomputed them all */
143 #define FIX(x) ((int32_t) ((x) * CONST_SCALE + 0.5))
144 
145 /* Descale and correctly round an int32_t value that's scaled by N bits.
146  * We assume RIGHT_SHIFT rounds towards minus infinity, so adding
147  * the fudge factor is correct for either sign of X.
148  */
149 
150 #define DESCALE(x,n) RIGHT_SHIFT((x) + (ONE << ((n)-1)), n)
151 
152 /* Multiply an int32_t variable by an int32_t constant to yield an int32_t result.
153  * For 8-bit samples with the recommended scaling, all the variable
154  * and constant values involved are no more than 16 bits wide, so a
155  * 16x16->32 bit multiply can be used instead of a full 32x32 multiply;
156  * this provides a useful speedup on many machines.
157  * There is no way to specify a 16x16->32 multiply in portable C, but
158  * some C compilers will do the right thing if you provide the correct
159  * combination of casts.
160  * NB: for 12-bit samples, a full 32-bit multiplication will be needed.
161  */
162 
163 #ifdef EIGHT_BIT_SAMPLES
164 #ifdef SHORTxSHORT_32 /* may work if 'int' is 32 bits */
165 #define MULTIPLY(var,const) (((int16_t) (var)) * ((int16_t) (const)))
166 #endif
167 #ifdef SHORTxLCONST_32 /* known to work with Microsoft C 6.0 */
168 #define MULTIPLY(var,const) (((int16_t) (var)) * ((int32_t) (const)))
169 #endif
170 #endif
171 
172 #ifndef MULTIPLY /* default definition */
173 #define MULTIPLY(var,const) ((var) * (const))
174 #endif
175 
176 
177 /*
178  Unlike our decoder where we approximate the FIXes, we need to use exact
179 ones here or successive P-frames will drift too much with Reference frame coding
180 */
181 #define FIX_0_211164243 1730
182 #define FIX_0_275899380 2260
183 #define FIX_0_298631336 2446
184 #define FIX_0_390180644 3196
185 #define FIX_0_509795579 4176
186 #define FIX_0_541196100 4433
187 #define FIX_0_601344887 4926
188 #define FIX_0_765366865 6270
189 #define FIX_0_785694958 6436
190 #define FIX_0_899976223 7373
191 #define FIX_1_061594337 8697
192 #define FIX_1_111140466 9102
193 #define FIX_1_175875602 9633
194 #define FIX_1_306562965 10703
195 #define FIX_1_387039845 11363
196 #define FIX_1_451774981 11893
197 #define FIX_1_501321110 12299
198 #define FIX_1_662939225 13623
199 #define FIX_1_847759065 15137
200 #define FIX_1_961570560 16069
201 #define FIX_2_053119869 16819
202 #define FIX_2_172734803 17799
203 #define FIX_2_562915447 20995
204 #define FIX_3_072711026 25172
205 
206 /*
207  * Perform the inverse DCT on one block of coefficients.
208  */
209 
210 void ff_j_rev_dct(DCTBLOCK data)
211 {
212  int32_t tmp0, tmp1, tmp2, tmp3;
213  int32_t tmp10, tmp11, tmp12, tmp13;
214  int32_t z1, z2, z3, z4, z5;
215  int32_t d0, d1, d2, d3, d4, d5, d6, d7;
216  register int16_t *dataptr;
217  int rowctr;
218 
219  /* Pass 1: process rows. */
220  /* Note results are scaled up by sqrt(8) compared to a true IDCT; */
221  /* furthermore, we scale the results by 2**PASS1_BITS. */
222 
223  dataptr = data;
224 
225  for (rowctr = DCTSIZE-1; rowctr >= 0; rowctr--) {
226  /* Due to quantization, we will usually find that many of the input
227  * coefficients are zero, especially the AC terms. We can exploit this
228  * by short-circuiting the IDCT calculation for any row in which all
229  * the AC terms are zero. In that case each output is equal to the
230  * DC coefficient (with scale factor as needed).
231  * With typical images and quantization tables, half or more of the
232  * row DCT calculations can be simplified this way.
233  */
234 
235  register int *idataptr = (int*)dataptr;
236 
237  /* WARNING: we do the same permutation as MMX idct to simplify the
238  video core */
239  d0 = dataptr[0];
240  d2 = dataptr[1];
241  d4 = dataptr[2];
242  d6 = dataptr[3];
243  d1 = dataptr[4];
244  d3 = dataptr[5];
245  d5 = dataptr[6];
246  d7 = dataptr[7];
247 
248  if ((d1 | d2 | d3 | d4 | d5 | d6 | d7) == 0) {
249  /* AC terms all zero */
250  if (d0) {
251  /* Compute a 32 bit value to assign. */
252  int16_t dcval = (int16_t) (d0 << PASS1_BITS);
253  register int v = (dcval & 0xffff) | ((dcval << 16) & 0xffff0000);
254 
255  idataptr[0] = v;
256  idataptr[1] = v;
257  idataptr[2] = v;
258  idataptr[3] = v;
259  }
260 
261  dataptr += DCTSIZE; /* advance pointer to next row */
262  continue;
263  }
264 
265  /* Even part: reverse the even part of the forward DCT. */
266  /* The rotator is sqrt(2)*c(-6). */
267 {
268  if (d6) {
269  if (d2) {
270  /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */
271  z1 = MULTIPLY(d2 + d6, FIX_0_541196100);
272  tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065);
273  tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865);
274 
275  tmp0 = (d0 + d4) << CONST_BITS;
276  tmp1 = (d0 - d4) << CONST_BITS;
277 
278  tmp10 = tmp0 + tmp3;
279  tmp13 = tmp0 - tmp3;
280  tmp11 = tmp1 + tmp2;
281  tmp12 = tmp1 - tmp2;
282  } else {
283  /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */
284  tmp2 = MULTIPLY(-d6, FIX_1_306562965);
285  tmp3 = MULTIPLY(d6, FIX_0_541196100);
286 
287  tmp0 = (d0 + d4) << CONST_BITS;
288  tmp1 = (d0 - d4) << CONST_BITS;
289 
290  tmp10 = tmp0 + tmp3;
291  tmp13 = tmp0 - tmp3;
292  tmp11 = tmp1 + tmp2;
293  tmp12 = tmp1 - tmp2;
294  }
295  } else {
296  if (d2) {
297  /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */
298  tmp2 = MULTIPLY(d2, FIX_0_541196100);
299  tmp3 = MULTIPLY(d2, FIX_1_306562965);
300 
301  tmp0 = (d0 + d4) << CONST_BITS;
302  tmp1 = (d0 - d4) << CONST_BITS;
303 
304  tmp10 = tmp0 + tmp3;
305  tmp13 = tmp0 - tmp3;
306  tmp11 = tmp1 + tmp2;
307  tmp12 = tmp1 - tmp2;
308  } else {
309  /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
310  tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
311  tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
312  }
313  }
314 
315  /* Odd part per figure 8; the matrix is unitary and hence its
316  * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
317  */
318 
319  if (d7) {
320  if (d5) {
321  if (d3) {
322  if (d1) {
323  /* d1 != 0, d3 != 0, d5 != 0, d7 != 0 */
324  z1 = d7 + d1;
325  z2 = d5 + d3;
326  z3 = d7 + d3;
327  z4 = d5 + d1;
328  z5 = MULTIPLY(z3 + z4, FIX_1_175875602);
329 
330  tmp0 = MULTIPLY(d7, FIX_0_298631336);
331  tmp1 = MULTIPLY(d5, FIX_2_053119869);
332  tmp2 = MULTIPLY(d3, FIX_3_072711026);
333  tmp3 = MULTIPLY(d1, FIX_1_501321110);
334  z1 = MULTIPLY(-z1, FIX_0_899976223);
335  z2 = MULTIPLY(-z2, FIX_2_562915447);
336  z3 = MULTIPLY(-z3, FIX_1_961570560);
337  z4 = MULTIPLY(-z4, FIX_0_390180644);
338 
339  z3 += z5;
340  z4 += z5;
341 
342  tmp0 += z1 + z3;
343  tmp1 += z2 + z4;
344  tmp2 += z2 + z3;
345  tmp3 += z1 + z4;
346  } else {
347  /* d1 == 0, d3 != 0, d5 != 0, d7 != 0 */
348  z2 = d5 + d3;
349  z3 = d7 + d3;
350  z5 = MULTIPLY(z3 + d5, FIX_1_175875602);
351 
352  tmp0 = MULTIPLY(d7, FIX_0_298631336);
353  tmp1 = MULTIPLY(d5, FIX_2_053119869);
354  tmp2 = MULTIPLY(d3, FIX_3_072711026);
355  z1 = MULTIPLY(-d7, FIX_0_899976223);
356  z2 = MULTIPLY(-z2, FIX_2_562915447);
357  z3 = MULTIPLY(-z3, FIX_1_961570560);
358  z4 = MULTIPLY(-d5, FIX_0_390180644);
359 
360  z3 += z5;
361  z4 += z5;
362 
363  tmp0 += z1 + z3;
364  tmp1 += z2 + z4;
365  tmp2 += z2 + z3;
366  tmp3 = z1 + z4;
367  }
368  } else {
369  if (d1) {
370  /* d1 != 0, d3 == 0, d5 != 0, d7 != 0 */
371  z1 = d7 + d1;
372  z4 = d5 + d1;
373  z5 = MULTIPLY(d7 + z4, FIX_1_175875602);
374 
375  tmp0 = MULTIPLY(d7, FIX_0_298631336);
376  tmp1 = MULTIPLY(d5, FIX_2_053119869);
377  tmp3 = MULTIPLY(d1, FIX_1_501321110);
378  z1 = MULTIPLY(-z1, FIX_0_899976223);
379  z2 = MULTIPLY(-d5, FIX_2_562915447);
380  z3 = MULTIPLY(-d7, FIX_1_961570560);
381  z4 = MULTIPLY(-z4, FIX_0_390180644);
382 
383  z3 += z5;
384  z4 += z5;
385 
386  tmp0 += z1 + z3;
387  tmp1 += z2 + z4;
388  tmp2 = z2 + z3;
389  tmp3 += z1 + z4;
390  } else {
391  /* d1 == 0, d3 == 0, d5 != 0, d7 != 0 */
392  tmp0 = MULTIPLY(-d7, FIX_0_601344887);
393  z1 = MULTIPLY(-d7, FIX_0_899976223);
394  z3 = MULTIPLY(-d7, FIX_1_961570560);
395  tmp1 = MULTIPLY(-d5, FIX_0_509795579);
396  z2 = MULTIPLY(-d5, FIX_2_562915447);
397  z4 = MULTIPLY(-d5, FIX_0_390180644);
398  z5 = MULTIPLY(d5 + d7, FIX_1_175875602);
399 
400  z3 += z5;
401  z4 += z5;
402 
403  tmp0 += z3;
404  tmp1 += z4;
405  tmp2 = z2 + z3;
406  tmp3 = z1 + z4;
407  }
408  }
409  } else {
410  if (d3) {
411  if (d1) {
412  /* d1 != 0, d3 != 0, d5 == 0, d7 != 0 */
413  z1 = d7 + d1;
414  z3 = d7 + d3;
415  z5 = MULTIPLY(z3 + d1, FIX_1_175875602);
416 
417  tmp0 = MULTIPLY(d7, FIX_0_298631336);
418  tmp2 = MULTIPLY(d3, FIX_3_072711026);
419  tmp3 = MULTIPLY(d1, FIX_1_501321110);
420  z1 = MULTIPLY(-z1, FIX_0_899976223);
421  z2 = MULTIPLY(-d3, FIX_2_562915447);
422  z3 = MULTIPLY(-z3, FIX_1_961570560);
423  z4 = MULTIPLY(-d1, FIX_0_390180644);
424 
425  z3 += z5;
426  z4 += z5;
427 
428  tmp0 += z1 + z3;
429  tmp1 = z2 + z4;
430  tmp2 += z2 + z3;
431  tmp3 += z1 + z4;
432  } else {
433  /* d1 == 0, d3 != 0, d5 == 0, d7 != 0 */
434  z3 = d7 + d3;
435 
436  tmp0 = MULTIPLY(-d7, FIX_0_601344887);
437  z1 = MULTIPLY(-d7, FIX_0_899976223);
438  tmp2 = MULTIPLY(d3, FIX_0_509795579);
439  z2 = MULTIPLY(-d3, FIX_2_562915447);
440  z5 = MULTIPLY(z3, FIX_1_175875602);
441  z3 = MULTIPLY(-z3, FIX_0_785694958);
442 
443  tmp0 += z3;
444  tmp1 = z2 + z5;
445  tmp2 += z3;
446  tmp3 = z1 + z5;
447  }
448  } else {
449  if (d1) {
450  /* d1 != 0, d3 == 0, d5 == 0, d7 != 0 */
451  z1 = d7 + d1;
452  z5 = MULTIPLY(z1, FIX_1_175875602);
453 
454  z1 = MULTIPLY(z1, FIX_0_275899380);
455  z3 = MULTIPLY(-d7, FIX_1_961570560);
456  tmp0 = MULTIPLY(-d7, FIX_1_662939225);
457  z4 = MULTIPLY(-d1, FIX_0_390180644);
458  tmp3 = MULTIPLY(d1, FIX_1_111140466);
459 
460  tmp0 += z1;
461  tmp1 = z4 + z5;
462  tmp2 = z3 + z5;
463  tmp3 += z1;
464  } else {
465  /* d1 == 0, d3 == 0, d5 == 0, d7 != 0 */
466  tmp0 = MULTIPLY(-d7, FIX_1_387039845);
467  tmp1 = MULTIPLY(d7, FIX_1_175875602);
468  tmp2 = MULTIPLY(-d7, FIX_0_785694958);
469  tmp3 = MULTIPLY(d7, FIX_0_275899380);
470  }
471  }
472  }
473  } else {
474  if (d5) {
475  if (d3) {
476  if (d1) {
477  /* d1 != 0, d3 != 0, d5 != 0, d7 == 0 */
478  z2 = d5 + d3;
479  z4 = d5 + d1;
480  z5 = MULTIPLY(d3 + z4, FIX_1_175875602);
481 
482  tmp1 = MULTIPLY(d5, FIX_2_053119869);
483  tmp2 = MULTIPLY(d3, FIX_3_072711026);
484  tmp3 = MULTIPLY(d1, FIX_1_501321110);
485  z1 = MULTIPLY(-d1, FIX_0_899976223);
486  z2 = MULTIPLY(-z2, FIX_2_562915447);
487  z3 = MULTIPLY(-d3, FIX_1_961570560);
488  z4 = MULTIPLY(-z4, FIX_0_390180644);
489 
490  z3 += z5;
491  z4 += z5;
492 
493  tmp0 = z1 + z3;
494  tmp1 += z2 + z4;
495  tmp2 += z2 + z3;
496  tmp3 += z1 + z4;
497  } else {
498  /* d1 == 0, d3 != 0, d5 != 0, d7 == 0 */
499  z2 = d5 + d3;
500 
501  z5 = MULTIPLY(z2, FIX_1_175875602);
502  tmp1 = MULTIPLY(d5, FIX_1_662939225);
503  z4 = MULTIPLY(-d5, FIX_0_390180644);
504  z2 = MULTIPLY(-z2, FIX_1_387039845);
505  tmp2 = MULTIPLY(d3, FIX_1_111140466);
506  z3 = MULTIPLY(-d3, FIX_1_961570560);
507 
508  tmp0 = z3 + z5;
509  tmp1 += z2;
510  tmp2 += z2;
511  tmp3 = z4 + z5;
512  }
513  } else {
514  if (d1) {
515  /* d1 != 0, d3 == 0, d5 != 0, d7 == 0 */
516  z4 = d5 + d1;
517 
518  z5 = MULTIPLY(z4, FIX_1_175875602);
519  z1 = MULTIPLY(-d1, FIX_0_899976223);
520  tmp3 = MULTIPLY(d1, FIX_0_601344887);
521  tmp1 = MULTIPLY(-d5, FIX_0_509795579);
522  z2 = MULTIPLY(-d5, FIX_2_562915447);
523  z4 = MULTIPLY(z4, FIX_0_785694958);
524 
525  tmp0 = z1 + z5;
526  tmp1 += z4;
527  tmp2 = z2 + z5;
528  tmp3 += z4;
529  } else {
530  /* d1 == 0, d3 == 0, d5 != 0, d7 == 0 */
531  tmp0 = MULTIPLY(d5, FIX_1_175875602);
532  tmp1 = MULTIPLY(d5, FIX_0_275899380);
533  tmp2 = MULTIPLY(-d5, FIX_1_387039845);
534  tmp3 = MULTIPLY(d5, FIX_0_785694958);
535  }
536  }
537  } else {
538  if (d3) {
539  if (d1) {
540  /* d1 != 0, d3 != 0, d5 == 0, d7 == 0 */
541  z5 = d1 + d3;
542  tmp3 = MULTIPLY(d1, FIX_0_211164243);
543  tmp2 = MULTIPLY(-d3, FIX_1_451774981);
544  z1 = MULTIPLY(d1, FIX_1_061594337);
545  z2 = MULTIPLY(-d3, FIX_2_172734803);
546  z4 = MULTIPLY(z5, FIX_0_785694958);
547  z5 = MULTIPLY(z5, FIX_1_175875602);
548 
549  tmp0 = z1 - z4;
550  tmp1 = z2 + z4;
551  tmp2 += z5;
552  tmp3 += z5;
553  } else {
554  /* d1 == 0, d3 != 0, d5 == 0, d7 == 0 */
555  tmp0 = MULTIPLY(-d3, FIX_0_785694958);
556  tmp1 = MULTIPLY(-d3, FIX_1_387039845);
557  tmp2 = MULTIPLY(-d3, FIX_0_275899380);
558  tmp3 = MULTIPLY(d3, FIX_1_175875602);
559  }
560  } else {
561  if (d1) {
562  /* d1 != 0, d3 == 0, d5 == 0, d7 == 0 */
563  tmp0 = MULTIPLY(d1, FIX_0_275899380);
564  tmp1 = MULTIPLY(d1, FIX_0_785694958);
565  tmp2 = MULTIPLY(d1, FIX_1_175875602);
566  tmp3 = MULTIPLY(d1, FIX_1_387039845);
567  } else {
568  /* d1 == 0, d3 == 0, d5 == 0, d7 == 0 */
569  tmp0 = tmp1 = tmp2 = tmp3 = 0;
570  }
571  }
572  }
573  }
574 }
575  /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
576 
577  dataptr[0] = (int16_t) DESCALE(tmp10 + tmp3, CONST_BITS-PASS1_BITS);
578  dataptr[7] = (int16_t) DESCALE(tmp10 - tmp3, CONST_BITS-PASS1_BITS);
579  dataptr[1] = (int16_t) DESCALE(tmp11 + tmp2, CONST_BITS-PASS1_BITS);
580  dataptr[6] = (int16_t) DESCALE(tmp11 - tmp2, CONST_BITS-PASS1_BITS);
581  dataptr[2] = (int16_t) DESCALE(tmp12 + tmp1, CONST_BITS-PASS1_BITS);
582  dataptr[5] = (int16_t) DESCALE(tmp12 - tmp1, CONST_BITS-PASS1_BITS);
583  dataptr[3] = (int16_t) DESCALE(tmp13 + tmp0, CONST_BITS-PASS1_BITS);
584  dataptr[4] = (int16_t) DESCALE(tmp13 - tmp0, CONST_BITS-PASS1_BITS);
585 
586  dataptr += DCTSIZE; /* advance pointer to next row */
587  }
588 
589  /* Pass 2: process columns. */
590  /* Note that we must descale the results by a factor of 8 == 2**3, */
591  /* and also undo the PASS1_BITS scaling. */
592 
593  dataptr = data;
594  for (rowctr = DCTSIZE-1; rowctr >= 0; rowctr--) {
595  /* Columns of zeroes can be exploited in the same way as we did with rows.
596  * However, the row calculation has created many nonzero AC terms, so the
597  * simplification applies less often (typically 5% to 10% of the time).
598  * On machines with very fast multiplication, it's possible that the
599  * test takes more time than it's worth. In that case this section
600  * may be commented out.
601  */
602 
603  d0 = dataptr[DCTSIZE*0];
604  d1 = dataptr[DCTSIZE*1];
605  d2 = dataptr[DCTSIZE*2];
606  d3 = dataptr[DCTSIZE*3];
607  d4 = dataptr[DCTSIZE*4];
608  d5 = dataptr[DCTSIZE*5];
609  d6 = dataptr[DCTSIZE*6];
610  d7 = dataptr[DCTSIZE*7];
611 
612  /* Even part: reverse the even part of the forward DCT. */
613  /* The rotator is sqrt(2)*c(-6). */
614  if (d6) {
615  if (d2) {
616  /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */
617  z1 = MULTIPLY(d2 + d6, FIX_0_541196100);
618  tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065);
619  tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865);
620 
621  tmp0 = (d0 + d4) << CONST_BITS;
622  tmp1 = (d0 - d4) << CONST_BITS;
623 
624  tmp10 = tmp0 + tmp3;
625  tmp13 = tmp0 - tmp3;
626  tmp11 = tmp1 + tmp2;
627  tmp12 = tmp1 - tmp2;
628  } else {
629  /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */
630  tmp2 = MULTIPLY(-d6, FIX_1_306562965);
631  tmp3 = MULTIPLY(d6, FIX_0_541196100);
632 
633  tmp0 = (d0 + d4) << CONST_BITS;
634  tmp1 = (d0 - d4) << CONST_BITS;
635 
636  tmp10 = tmp0 + tmp3;
637  tmp13 = tmp0 - tmp3;
638  tmp11 = tmp1 + tmp2;
639  tmp12 = tmp1 - tmp2;
640  }
641  } else {
642  if (d2) {
643  /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */
644  tmp2 = MULTIPLY(d2, FIX_0_541196100);
645  tmp3 = MULTIPLY(d2, FIX_1_306562965);
646 
647  tmp0 = (d0 + d4) << CONST_BITS;
648  tmp1 = (d0 - d4) << CONST_BITS;
649 
650  tmp10 = tmp0 + tmp3;
651  tmp13 = tmp0 - tmp3;
652  tmp11 = tmp1 + tmp2;
653  tmp12 = tmp1 - tmp2;
654  } else {
655  /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
656  tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
657  tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
658  }
659  }
660 
661  /* Odd part per figure 8; the matrix is unitary and hence its
662  * transpose is its inverse. i0..i3 are y7,y5,y3,y1 respectively.
663  */
664  if (d7) {
665  if (d5) {
666  if (d3) {
667  if (d1) {
668  /* d1 != 0, d3 != 0, d5 != 0, d7 != 0 */
669  z1 = d7 + d1;
670  z2 = d5 + d3;
671  z3 = d7 + d3;
672  z4 = d5 + d1;
673  z5 = MULTIPLY(z3 + z4, FIX_1_175875602);
674 
675  tmp0 = MULTIPLY(d7, FIX_0_298631336);
676  tmp1 = MULTIPLY(d5, FIX_2_053119869);
677  tmp2 = MULTIPLY(d3, FIX_3_072711026);
678  tmp3 = MULTIPLY(d1, FIX_1_501321110);
679  z1 = MULTIPLY(-z1, FIX_0_899976223);
680  z2 = MULTIPLY(-z2, FIX_2_562915447);
681  z3 = MULTIPLY(-z3, FIX_1_961570560);
682  z4 = MULTIPLY(-z4, FIX_0_390180644);
683 
684  z3 += z5;
685  z4 += z5;
686 
687  tmp0 += z1 + z3;
688  tmp1 += z2 + z4;
689  tmp2 += z2 + z3;
690  tmp3 += z1 + z4;
691  } else {
692  /* d1 == 0, d3 != 0, d5 != 0, d7 != 0 */
693  z2 = d5 + d3;
694  z3 = d7 + d3;
695  z5 = MULTIPLY(z3 + d5, FIX_1_175875602);
696 
697  tmp0 = MULTIPLY(d7, FIX_0_298631336);
698  tmp1 = MULTIPLY(d5, FIX_2_053119869);
699  tmp2 = MULTIPLY(d3, FIX_3_072711026);
700  z1 = MULTIPLY(-d7, FIX_0_899976223);
701  z2 = MULTIPLY(-z2, FIX_2_562915447);
702  z3 = MULTIPLY(-z3, FIX_1_961570560);
703  z4 = MULTIPLY(-d5, FIX_0_390180644);
704 
705  z3 += z5;
706  z4 += z5;
707 
708  tmp0 += z1 + z3;
709  tmp1 += z2 + z4;
710  tmp2 += z2 + z3;
711  tmp3 = z1 + z4;
712  }
713  } else {
714  if (d1) {
715  /* d1 != 0, d3 == 0, d5 != 0, d7 != 0 */
716  z1 = d7 + d1;
717  z3 = d7;
718  z4 = d5 + d1;
719  z5 = MULTIPLY(z3 + z4, FIX_1_175875602);
720 
721  tmp0 = MULTIPLY(d7, FIX_0_298631336);
722  tmp1 = MULTIPLY(d5, FIX_2_053119869);
723  tmp3 = MULTIPLY(d1, FIX_1_501321110);
724  z1 = MULTIPLY(-z1, FIX_0_899976223);
725  z2 = MULTIPLY(-d5, FIX_2_562915447);
726  z3 = MULTIPLY(-d7, FIX_1_961570560);
727  z4 = MULTIPLY(-z4, FIX_0_390180644);
728 
729  z3 += z5;
730  z4 += z5;
731 
732  tmp0 += z1 + z3;
733  tmp1 += z2 + z4;
734  tmp2 = z2 + z3;
735  tmp3 += z1 + z4;
736  } else {
737  /* d1 == 0, d3 == 0, d5 != 0, d7 != 0 */
738  tmp0 = MULTIPLY(-d7, FIX_0_601344887);
739  z1 = MULTIPLY(-d7, FIX_0_899976223);
740  z3 = MULTIPLY(-d7, FIX_1_961570560);
741  tmp1 = MULTIPLY(-d5, FIX_0_509795579);
742  z2 = MULTIPLY(-d5, FIX_2_562915447);
743  z4 = MULTIPLY(-d5, FIX_0_390180644);
744  z5 = MULTIPLY(d5 + d7, FIX_1_175875602);
745 
746  z3 += z5;
747  z4 += z5;
748 
749  tmp0 += z3;
750  tmp1 += z4;
751  tmp2 = z2 + z3;
752  tmp3 = z1 + z4;
753  }
754  }
755  } else {
756  if (d3) {
757  if (d1) {
758  /* d1 != 0, d3 != 0, d5 == 0, d7 != 0 */
759  z1 = d7 + d1;
760  z3 = d7 + d3;
761  z5 = MULTIPLY(z3 + d1, FIX_1_175875602);
762 
763  tmp0 = MULTIPLY(d7, FIX_0_298631336);
764  tmp2 = MULTIPLY(d3, FIX_3_072711026);
765  tmp3 = MULTIPLY(d1, FIX_1_501321110);
766  z1 = MULTIPLY(-z1, FIX_0_899976223);
767  z2 = MULTIPLY(-d3, FIX_2_562915447);
768  z3 = MULTIPLY(-z3, FIX_1_961570560);
769  z4 = MULTIPLY(-d1, FIX_0_390180644);
770 
771  z3 += z5;
772  z4 += z5;
773 
774  tmp0 += z1 + z3;
775  tmp1 = z2 + z4;
776  tmp2 += z2 + z3;
777  tmp3 += z1 + z4;
778  } else {
779  /* d1 == 0, d3 != 0, d5 == 0, d7 != 0 */
780  z3 = d7 + d3;
781 
782  tmp0 = MULTIPLY(-d7, FIX_0_601344887);
783  z1 = MULTIPLY(-d7, FIX_0_899976223);
784  tmp2 = MULTIPLY(d3, FIX_0_509795579);
785  z2 = MULTIPLY(-d3, FIX_2_562915447);
786  z5 = MULTIPLY(z3, FIX_1_175875602);
787  z3 = MULTIPLY(-z3, FIX_0_785694958);
788 
789  tmp0 += z3;
790  tmp1 = z2 + z5;
791  tmp2 += z3;
792  tmp3 = z1 + z5;
793  }
794  } else {
795  if (d1) {
796  /* d1 != 0, d3 == 0, d5 == 0, d7 != 0 */
797  z1 = d7 + d1;
798  z5 = MULTIPLY(z1, FIX_1_175875602);
799 
800  z1 = MULTIPLY(z1, FIX_0_275899380);
801  z3 = MULTIPLY(-d7, FIX_1_961570560);
802  tmp0 = MULTIPLY(-d7, FIX_1_662939225);
803  z4 = MULTIPLY(-d1, FIX_0_390180644);
804  tmp3 = MULTIPLY(d1, FIX_1_111140466);
805 
806  tmp0 += z1;
807  tmp1 = z4 + z5;
808  tmp2 = z3 + z5;
809  tmp3 += z1;
810  } else {
811  /* d1 == 0, d3 == 0, d5 == 0, d7 != 0 */
812  tmp0 = MULTIPLY(-d7, FIX_1_387039845);
813  tmp1 = MULTIPLY(d7, FIX_1_175875602);
814  tmp2 = MULTIPLY(-d7, FIX_0_785694958);
815  tmp3 = MULTIPLY(d7, FIX_0_275899380);
816  }
817  }
818  }
819  } else {
820  if (d5) {
821  if (d3) {
822  if (d1) {
823  /* d1 != 0, d3 != 0, d5 != 0, d7 == 0 */
824  z2 = d5 + d3;
825  z4 = d5 + d1;
826  z5 = MULTIPLY(d3 + z4, FIX_1_175875602);
827 
828  tmp1 = MULTIPLY(d5, FIX_2_053119869);
829  tmp2 = MULTIPLY(d3, FIX_3_072711026);
830  tmp3 = MULTIPLY(d1, FIX_1_501321110);
831  z1 = MULTIPLY(-d1, FIX_0_899976223);
832  z2 = MULTIPLY(-z2, FIX_2_562915447);
833  z3 = MULTIPLY(-d3, FIX_1_961570560);
834  z4 = MULTIPLY(-z4, FIX_0_390180644);
835 
836  z3 += z5;
837  z4 += z5;
838 
839  tmp0 = z1 + z3;
840  tmp1 += z2 + z4;
841  tmp2 += z2 + z3;
842  tmp3 += z1 + z4;
843  } else {
844  /* d1 == 0, d3 != 0, d5 != 0, d7 == 0 */
845  z2 = d5 + d3;
846 
847  z5 = MULTIPLY(z2, FIX_1_175875602);
848  tmp1 = MULTIPLY(d5, FIX_1_662939225);
849  z4 = MULTIPLY(-d5, FIX_0_390180644);
850  z2 = MULTIPLY(-z2, FIX_1_387039845);
851  tmp2 = MULTIPLY(d3, FIX_1_111140466);
852  z3 = MULTIPLY(-d3, FIX_1_961570560);
853 
854  tmp0 = z3 + z5;
855  tmp1 += z2;
856  tmp2 += z2;
857  tmp3 = z4 + z5;
858  }
859  } else {
860  if (d1) {
861  /* d1 != 0, d3 == 0, d5 != 0, d7 == 0 */
862  z4 = d5 + d1;
863 
864  z5 = MULTIPLY(z4, FIX_1_175875602);
865  z1 = MULTIPLY(-d1, FIX_0_899976223);
866  tmp3 = MULTIPLY(d1, FIX_0_601344887);
867  tmp1 = MULTIPLY(-d5, FIX_0_509795579);
868  z2 = MULTIPLY(-d5, FIX_2_562915447);
869  z4 = MULTIPLY(z4, FIX_0_785694958);
870 
871  tmp0 = z1 + z5;
872  tmp1 += z4;
873  tmp2 = z2 + z5;
874  tmp3 += z4;
875  } else {
876  /* d1 == 0, d3 == 0, d5 != 0, d7 == 0 */
877  tmp0 = MULTIPLY(d5, FIX_1_175875602);
878  tmp1 = MULTIPLY(d5, FIX_0_275899380);
879  tmp2 = MULTIPLY(-d5, FIX_1_387039845);
880  tmp3 = MULTIPLY(d5, FIX_0_785694958);
881  }
882  }
883  } else {
884  if (d3) {
885  if (d1) {
886  /* d1 != 0, d3 != 0, d5 == 0, d7 == 0 */
887  z5 = d1 + d3;
888  tmp3 = MULTIPLY(d1, FIX_0_211164243);
889  tmp2 = MULTIPLY(-d3, FIX_1_451774981);
890  z1 = MULTIPLY(d1, FIX_1_061594337);
891  z2 = MULTIPLY(-d3, FIX_2_172734803);
892  z4 = MULTIPLY(z5, FIX_0_785694958);
893  z5 = MULTIPLY(z5, FIX_1_175875602);
894 
895  tmp0 = z1 - z4;
896  tmp1 = z2 + z4;
897  tmp2 += z5;
898  tmp3 += z5;
899  } else {
900  /* d1 == 0, d3 != 0, d5 == 0, d7 == 0 */
901  tmp0 = MULTIPLY(-d3, FIX_0_785694958);
902  tmp1 = MULTIPLY(-d3, FIX_1_387039845);
903  tmp2 = MULTIPLY(-d3, FIX_0_275899380);
904  tmp3 = MULTIPLY(d3, FIX_1_175875602);
905  }
906  } else {
907  if (d1) {
908  /* d1 != 0, d3 == 0, d5 == 0, d7 == 0 */
909  tmp0 = MULTIPLY(d1, FIX_0_275899380);
910  tmp1 = MULTIPLY(d1, FIX_0_785694958);
911  tmp2 = MULTIPLY(d1, FIX_1_175875602);
912  tmp3 = MULTIPLY(d1, FIX_1_387039845);
913  } else {
914  /* d1 == 0, d3 == 0, d5 == 0, d7 == 0 */
915  tmp0 = tmp1 = tmp2 = tmp3 = 0;
916  }
917  }
918  }
919  }
920 
921  /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
922 
923  dataptr[DCTSIZE*0] = (int16_t) DESCALE(tmp10 + tmp3,
924  CONST_BITS+PASS1_BITS+3);
925  dataptr[DCTSIZE*7] = (int16_t) DESCALE(tmp10 - tmp3,
926  CONST_BITS+PASS1_BITS+3);
927  dataptr[DCTSIZE*1] = (int16_t) DESCALE(tmp11 + tmp2,
928  CONST_BITS+PASS1_BITS+3);
929  dataptr[DCTSIZE*6] = (int16_t) DESCALE(tmp11 - tmp2,
930  CONST_BITS+PASS1_BITS+3);
931  dataptr[DCTSIZE*2] = (int16_t) DESCALE(tmp12 + tmp1,
932  CONST_BITS+PASS1_BITS+3);
933  dataptr[DCTSIZE*5] = (int16_t) DESCALE(tmp12 - tmp1,
934  CONST_BITS+PASS1_BITS+3);
935  dataptr[DCTSIZE*3] = (int16_t) DESCALE(tmp13 + tmp0,
936  CONST_BITS+PASS1_BITS+3);
937  dataptr[DCTSIZE*4] = (int16_t) DESCALE(tmp13 - tmp0,
938  CONST_BITS+PASS1_BITS+3);
939 
940  dataptr++; /* advance pointer to next column */
941  }
942 }
943 
944 #undef DCTSIZE
945 #define DCTSIZE 4
946 #define DCTSTRIDE 8
947 
948 void ff_j_rev_dct4(DCTBLOCK data)
949 {
950  int32_t tmp0, tmp1, tmp2, tmp3;
951  int32_t tmp10, tmp11, tmp12, tmp13;
952  int32_t z1;
953  int32_t d0, d2, d4, d6;
954  register int16_t *dataptr;
955  int rowctr;
956 
957  /* Pass 1: process rows. */
958  /* Note results are scaled up by sqrt(8) compared to a true IDCT; */
959  /* furthermore, we scale the results by 2**PASS1_BITS. */
960 
961  data[0] += 4;
962 
963  dataptr = data;
964 
965  for (rowctr = DCTSIZE-1; rowctr >= 0; rowctr--) {
966  /* Due to quantization, we will usually find that many of the input
967  * coefficients are zero, especially the AC terms. We can exploit this
968  * by short-circuiting the IDCT calculation for any row in which all
969  * the AC terms are zero. In that case each output is equal to the
970  * DC coefficient (with scale factor as needed).
971  * With typical images and quantization tables, half or more of the
972  * row DCT calculations can be simplified this way.
973  */
974 
975  register int *idataptr = (int*)dataptr;
976 
977  d0 = dataptr[0];
978  d2 = dataptr[1];
979  d4 = dataptr[2];
980  d6 = dataptr[3];
981 
982  if ((d2 | d4 | d6) == 0) {
983  /* AC terms all zero */
984  if (d0) {
985  /* Compute a 32 bit value to assign. */
986  int16_t dcval = (int16_t) (d0 << PASS1_BITS);
987  register int v = (dcval & 0xffff) | ((dcval << 16) & 0xffff0000);
988 
989  idataptr[0] = v;
990  idataptr[1] = v;
991  }
992 
993  dataptr += DCTSTRIDE; /* advance pointer to next row */
994  continue;
995  }
996 
997  /* Even part: reverse the even part of the forward DCT. */
998  /* The rotator is sqrt(2)*c(-6). */
999  if (d6) {
1000  if (d2) {
1001  /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */
1002  z1 = MULTIPLY(d2 + d6, FIX_0_541196100);
1003  tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065);
1004  tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865);
1005 
1006  tmp0 = (d0 + d4) << CONST_BITS;
1007  tmp1 = (d0 - d4) << CONST_BITS;
1008 
1009  tmp10 = tmp0 + tmp3;
1010  tmp13 = tmp0 - tmp3;
1011  tmp11 = tmp1 + tmp2;
1012  tmp12 = tmp1 - tmp2;
1013  } else {
1014  /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */
1015  tmp2 = MULTIPLY(-d6, FIX_1_306562965);
1016  tmp3 = MULTIPLY(d6, FIX_0_541196100);
1017 
1018  tmp0 = (d0 + d4) << CONST_BITS;
1019  tmp1 = (d0 - d4) << CONST_BITS;
1020 
1021  tmp10 = tmp0 + tmp3;
1022  tmp13 = tmp0 - tmp3;
1023  tmp11 = tmp1 + tmp2;
1024  tmp12 = tmp1 - tmp2;
1025  }
1026  } else {
1027  if (d2) {
1028  /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */
1029  tmp2 = MULTIPLY(d2, FIX_0_541196100);
1030  tmp3 = MULTIPLY(d2, FIX_1_306562965);
1031 
1032  tmp0 = (d0 + d4) << CONST_BITS;
1033  tmp1 = (d0 - d4) << CONST_BITS;
1034 
1035  tmp10 = tmp0 + tmp3;
1036  tmp13 = tmp0 - tmp3;
1037  tmp11 = tmp1 + tmp2;
1038  tmp12 = tmp1 - tmp2;
1039  } else {
1040  /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
1041  tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
1042  tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
1043  }
1044  }
1045 
1046  /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
1047 
1048  dataptr[0] = (int16_t) DESCALE(tmp10, CONST_BITS-PASS1_BITS);
1049  dataptr[1] = (int16_t) DESCALE(tmp11, CONST_BITS-PASS1_BITS);
1050  dataptr[2] = (int16_t) DESCALE(tmp12, CONST_BITS-PASS1_BITS);
1051  dataptr[3] = (int16_t) DESCALE(tmp13, CONST_BITS-PASS1_BITS);
1052 
1053  dataptr += DCTSTRIDE; /* advance pointer to next row */
1054  }
1055 
1056  /* Pass 2: process columns. */
1057  /* Note that we must descale the results by a factor of 8 == 2**3, */
1058  /* and also undo the PASS1_BITS scaling. */
1059 
1060  dataptr = data;
1061  for (rowctr = DCTSIZE-1; rowctr >= 0; rowctr--) {
1062  /* Columns of zeroes can be exploited in the same way as we did with rows.
1063  * However, the row calculation has created many nonzero AC terms, so the
1064  * simplification applies less often (typically 5% to 10% of the time).
1065  * On machines with very fast multiplication, it's possible that the
1066  * test takes more time than it's worth. In that case this section
1067  * may be commented out.
1068  */
1069 
1070  d0 = dataptr[DCTSTRIDE*0];
1071  d2 = dataptr[DCTSTRIDE*1];
1072  d4 = dataptr[DCTSTRIDE*2];
1073  d6 = dataptr[DCTSTRIDE*3];
1074 
1075  /* Even part: reverse the even part of the forward DCT. */
1076  /* The rotator is sqrt(2)*c(-6). */
1077  if (d6) {
1078  if (d2) {
1079  /* d0 != 0, d2 != 0, d4 != 0, d6 != 0 */
1080  z1 = MULTIPLY(d2 + d6, FIX_0_541196100);
1081  tmp2 = z1 + MULTIPLY(-d6, FIX_1_847759065);
1082  tmp3 = z1 + MULTIPLY(d2, FIX_0_765366865);
1083 
1084  tmp0 = (d0 + d4) << CONST_BITS;
1085  tmp1 = (d0 - d4) << CONST_BITS;
1086 
1087  tmp10 = tmp0 + tmp3;
1088  tmp13 = tmp0 - tmp3;
1089  tmp11 = tmp1 + tmp2;
1090  tmp12 = tmp1 - tmp2;
1091  } else {
1092  /* d0 != 0, d2 == 0, d4 != 0, d6 != 0 */
1093  tmp2 = MULTIPLY(-d6, FIX_1_306562965);
1094  tmp3 = MULTIPLY(d6, FIX_0_541196100);
1095 
1096  tmp0 = (d0 + d4) << CONST_BITS;
1097  tmp1 = (d0 - d4) << CONST_BITS;
1098 
1099  tmp10 = tmp0 + tmp3;
1100  tmp13 = tmp0 - tmp3;
1101  tmp11 = tmp1 + tmp2;
1102  tmp12 = tmp1 - tmp2;
1103  }
1104  } else {
1105  if (d2) {
1106  /* d0 != 0, d2 != 0, d4 != 0, d6 == 0 */
1107  tmp2 = MULTIPLY(d2, FIX_0_541196100);
1108  tmp3 = MULTIPLY(d2, FIX_1_306562965);
1109 
1110  tmp0 = (d0 + d4) << CONST_BITS;
1111  tmp1 = (d0 - d4) << CONST_BITS;
1112 
1113  tmp10 = tmp0 + tmp3;
1114  tmp13 = tmp0 - tmp3;
1115  tmp11 = tmp1 + tmp2;
1116  tmp12 = tmp1 - tmp2;
1117  } else {
1118  /* d0 != 0, d2 == 0, d4 != 0, d6 == 0 */
1119  tmp10 = tmp13 = (d0 + d4) << CONST_BITS;
1120  tmp11 = tmp12 = (d0 - d4) << CONST_BITS;
1121  }
1122  }
1123 
1124  /* Final output stage: inputs are tmp10..tmp13, tmp0..tmp3 */
1125 
1126  dataptr[DCTSTRIDE*0] = tmp10 >> (CONST_BITS+PASS1_BITS+3);
1127  dataptr[DCTSTRIDE*1] = tmp11 >> (CONST_BITS+PASS1_BITS+3);
1128  dataptr[DCTSTRIDE*2] = tmp12 >> (CONST_BITS+PASS1_BITS+3);
1129  dataptr[DCTSTRIDE*3] = tmp13 >> (CONST_BITS+PASS1_BITS+3);
1130 
1131  dataptr++; /* advance pointer to next column */
1132  }
1133 }
1134 
1135 void ff_j_rev_dct2(DCTBLOCK data){
1136  int d00, d01, d10, d11;
1137 
1138  data[0] += 4;
1139  d00 = data[0+0*DCTSTRIDE] + data[1+0*DCTSTRIDE];
1140  d01 = data[0+0*DCTSTRIDE] - data[1+0*DCTSTRIDE];
1141  d10 = data[0+1*DCTSTRIDE] + data[1+1*DCTSTRIDE];
1142  d11 = data[0+1*DCTSTRIDE] - data[1+1*DCTSTRIDE];
1143 
1144  data[0+0*DCTSTRIDE]= (d00 + d10)>>3;
1145  data[1+0*DCTSTRIDE]= (d01 + d11)>>3;
1146  data[0+1*DCTSTRIDE]= (d00 - d10)>>3;
1147  data[1+1*DCTSTRIDE]= (d01 - d11)>>3;
1148 }
1149 
1150 void ff_j_rev_dct1(DCTBLOCK data){
1151  data[0] = (data[0] + 4)>>3;
1152 }
1153 
1154 #undef FIX
1155 #undef CONST_BITS
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