FFmpeg coverage

Directory: ../../../ffmpeg/
File: src/libavcodec/jfdctint_template.c
Date: 2025-10-29 00:48:36
Exec Total Coverage
Lines: 83 115 72.2%
Functions: 4 6 66.7%
Branches: 4 6 66.7%
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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) 1991-1996, 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 a slow-but-accurate integer implementation of the
40 * forward DCT (Discrete Cosine Transform).
41 *
42 * A 2-D DCT can be done by 1-D DCT on each row followed by 1-D DCT
43 * on each column. Direct algorithms are also available, but they are
44 * much more complex and seem not to be any faster when reduced to code.
45 *
46 * This implementation is based on an algorithm described in
47 * C. Loeffler, A. Ligtenberg and G. Moschytz, "Practical Fast 1-D DCT
48 * Algorithms with 11 Multiplications", Proc. Int'l. Conf. on Acoustics,
49 * Speech, and Signal Processing 1989 (ICASSP '89), pp. 988-991.
50 * The primary algorithm described there uses 11 multiplies and 29 adds.
51 * We use their alternate method with 12 multiplies and 32 adds.
52 * The advantage of this method is that no data path contains more than one
53 * multiplication; this allows a very simple and accurate implementation in
54 * scaled fixed-point arithmetic, with a minimal number of shifts.
55 */
56
57 /**
58 * @file
59 * Independent JPEG Group's slow & accurate dct.
60 */
61
62 #include "libavutil/common.h"
63 #include "fdctdsp.h"
64
65 #include "bit_depth_template.c"
66
67 #define DCTSIZE 8
68 #define BITS_IN_JSAMPLE BIT_DEPTH
69 #define GLOBAL(x) x
70 #define RIGHT_SHIFT(x, n) ((x) >> (n))
71 #define MULTIPLY16C16(var,const) ((var)*(const))
72 #define DESCALE(x,n) RIGHT_SHIFT((int)(x) + (1 << ((n) - 1)), n)
73
74
75 /*
76 * This module is specialized to the case DCTSIZE = 8.
77 */
78
79 #if DCTSIZE != 8
80 #error "Sorry, this code only copes with 8x8 DCTs."
81 #endif
82
83
84 /*
85 * The poop on this scaling stuff is as follows:
86 *
87 * Each 1-D DCT step produces outputs which are a factor of sqrt(N)
88 * larger than the true DCT outputs. The final outputs are therefore
89 * a factor of N larger than desired; since N=8 this can be cured by
90 * a simple right shift at the end of the algorithm. The advantage of
91 * this arrangement is that we save two multiplications per 1-D DCT,
92 * because the y0 and y4 outputs need not be divided by sqrt(N).
93 * In the IJG code, this factor of 8 is removed by the quantization step
94 * (in jcdctmgr.c), NOT in this module.
95 *
96 * We have to do addition and subtraction of the integer inputs, which
97 * is no problem, and multiplication by fractional constants, which is
98 * a problem to do in integer arithmetic. We multiply all the constants
99 * by CONST_SCALE and convert them to integer constants (thus retaining
100 * CONST_BITS bits of precision in the constants). After doing a
101 * multiplication we have to divide the product by CONST_SCALE, with proper
102 * rounding, to produce the correct output. This division can be done
103 * cheaply as a right shift of CONST_BITS bits. We postpone shifting
104 * as long as possible so that partial sums can be added together with
105 * full fractional precision.
106 *
107 * The outputs of the first pass are scaled up by PASS1_BITS bits so that
108 * they are represented to better-than-integral precision. These outputs
109 * require BITS_IN_JSAMPLE + PASS1_BITS + 3 bits; this fits in a 16-bit word
110 * with the recommended scaling. (For 12-bit sample data, the intermediate
111 * array is int32_t anyway.)
112 *
113 * To avoid overflow of the 32-bit intermediate results in pass 2, we must
114 * have BITS_IN_JSAMPLE + CONST_BITS + PASS1_BITS <= 26. Error analysis
115 * shows that the values given below are the most effective.
116 */
117
118 #undef CONST_BITS
119 #undef PASS1_BITS
120 #undef OUT_SHIFT
121
122 #if BITS_IN_JSAMPLE == 8
123 #define CONST_BITS 13
124 #define PASS1_BITS 4 /* set this to 2 if 16x16 multiplies are faster */
125 #define OUT_SHIFT PASS1_BITS
126 #else
127 #define CONST_BITS 13
128 #define PASS1_BITS 1 /* lose a little precision to avoid overflow */
129 #define OUT_SHIFT (PASS1_BITS + 1)
130 #endif
131
132 /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus
133 * causing a lot of useless floating-point operations at run time.
134 * To get around this we use the following pre-calculated constants.
135 * If you change CONST_BITS you may want to add appropriate values.
136 * (With a reasonable C compiler, you can just rely on the FIX() macro...)
137 */
138
139 #if CONST_BITS == 13
140 #define FIX_0_298631336 ((int32_t) 2446) /* FIX(0.298631336) */
141 #define FIX_0_390180644 ((int32_t) 3196) /* FIX(0.390180644) */
142 #define FIX_0_541196100 ((int32_t) 4433) /* FIX(0.541196100) */
143 #define FIX_0_765366865 ((int32_t) 6270) /* FIX(0.765366865) */
144 #define FIX_0_899976223 ((int32_t) 7373) /* FIX(0.899976223) */
145 #define FIX_1_175875602 ((int32_t) 9633) /* FIX(1.175875602) */
146 #define FIX_1_501321110 ((int32_t) 12299) /* FIX(1.501321110) */
147 #define FIX_1_847759065 ((int32_t) 15137) /* FIX(1.847759065) */
148 #define FIX_1_961570560 ((int32_t) 16069) /* FIX(1.961570560) */
149 #define FIX_2_053119869 ((int32_t) 16819) /* FIX(2.053119869) */
150 #define FIX_2_562915447 ((int32_t) 20995) /* FIX(2.562915447) */
151 #define FIX_3_072711026 ((int32_t) 25172) /* FIX(3.072711026) */
152 #else
153 #define FIX_0_298631336 FIX(0.298631336)
154 #define FIX_0_390180644 FIX(0.390180644)
155 #define FIX_0_541196100 FIX(0.541196100)
156 #define FIX_0_765366865 FIX(0.765366865)
157 #define FIX_0_899976223 FIX(0.899976223)
158 #define FIX_1_175875602 FIX(1.175875602)
159 #define FIX_1_501321110 FIX(1.501321110)
160 #define FIX_1_847759065 FIX(1.847759065)
161 #define FIX_1_961570560 FIX(1.961570560)
162 #define FIX_2_053119869 FIX(2.053119869)
163 #define FIX_2_562915447 FIX(2.562915447)
164 #define FIX_3_072711026 FIX(3.072711026)
165 #endif
166
167
168 /* Multiply an int32_t variable by an int32_t constant to yield an int32_t result.
169 * For 8-bit samples with the recommended scaling, all the variable
170 * and constant values involved are no more than 16 bits wide, so a
171 * 16x16->32 bit multiply can be used instead of a full 32x32 multiply.
172 * For 12-bit samples, a full 32-bit multiplication will be needed.
173 */
174
175 #if BITS_IN_JSAMPLE == 8 && CONST_BITS<=13 && PASS1_BITS<=2
176 #define MULTIPLY(var,const) MULTIPLY16C16(var,const)
177 #else
178 #define MULTIPLY(var,const) (int)((var) * (unsigned)(const))
179 #endif
180
181
182 54357822 static av_always_inline void FUNC(row_fdct)(int16_t *data)
183 {
184 int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
185 int tmp10, tmp11, tmp12, tmp13;
186 unsigned z1, z2, z3, z4, z5;
187 int16_t *dataptr;
188 int ctr;
189
190 /* Pass 1: process rows. */
191 /* Note results are scaled up by sqrt(8) compared to a true DCT; */
192 /* furthermore, we scale the results by 2**PASS1_BITS. */
193
194 54357822 dataptr = data;
195
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 489220398 for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
196 434862576 tmp0 = dataptr[0] + dataptr[7];
197 434862576 tmp7 = dataptr[0] - dataptr[7];
198 434862576 tmp1 = dataptr[1] + dataptr[6];
199 434862576 tmp6 = dataptr[1] - dataptr[6];
200 434862576 tmp2 = dataptr[2] + dataptr[5];
201 434862576 tmp5 = dataptr[2] - dataptr[5];
202 434862576 tmp3 = dataptr[3] + dataptr[4];
203 434862576 tmp4 = dataptr[3] - dataptr[4];
204
205 /* Even part per LL&M figure 1 --- note that published figure is faulty;
206 * rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
207 */
208
209 434862576 tmp10 = tmp0 + tmp3;
210 434862576 tmp13 = tmp0 - tmp3;
211 434862576 tmp11 = tmp1 + tmp2;
212 434862576 tmp12 = tmp1 - tmp2;
213
214 434862576 dataptr[0] = (int16_t) ((tmp10 + tmp11) * (1 << PASS1_BITS));
215 434862576 dataptr[4] = (int16_t) ((tmp10 - tmp11) * (1 << PASS1_BITS));
216
217 434862576 z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
218 434862576 dataptr[2] = (int16_t) DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
219 CONST_BITS-PASS1_BITS);
220 434862576 dataptr[6] = (int16_t) DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
221 CONST_BITS-PASS1_BITS);
222
223 /* Odd part per figure 8 --- note paper omits factor of sqrt(2).
224 * cK represents cos(K*pi/16).
225 * i0..i3 in the paper are tmp4..tmp7 here.
226 */
227
228 434862576 z1 = tmp4 + tmp7;
229 434862576 z2 = tmp5 + tmp6;
230 434862576 z3 = tmp4 + tmp6;
231 434862576 z4 = tmp5 + tmp7;
232 434862576 z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
233
234 434862576 tmp4 = MULTIPLY(tmp4, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
235 434862576 tmp5 = MULTIPLY(tmp5, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
236 434862576 tmp6 = MULTIPLY(tmp6, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
237 434862576 tmp7 = MULTIPLY(tmp7, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
238 434862576 z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
239 434862576 z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
240 434862576 z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
241 434862576 z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
242
243 434862576 z3 += z5;
244 434862576 z4 += z5;
245
246 434862576 dataptr[7] = (int16_t) DESCALE(tmp4 + z1 + z3, CONST_BITS-PASS1_BITS);
247 434862576 dataptr[5] = (int16_t) DESCALE(tmp5 + z2 + z4, CONST_BITS-PASS1_BITS);
248 434862576 dataptr[3] = (int16_t) DESCALE(tmp6 + z2 + z3, CONST_BITS-PASS1_BITS);
249 434862576 dataptr[1] = (int16_t) DESCALE(tmp7 + z1 + z4, CONST_BITS-PASS1_BITS);
250
251 434862576 dataptr += DCTSIZE; /* advance pointer to next row */
252 }
253 54357822 }
254
255 /*
256 * Perform the forward DCT on one block of samples.
257 */
258
259 GLOBAL(void)
260 54357822 FUNC(ff_jpeg_fdct_islow)(int16_t *data)
261 {
262 int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
263 int tmp10, tmp11, tmp12, tmp13;
264 unsigned z1, z2, z3, z4, z5;
265 int16_t *dataptr;
266 int ctr;
267
268 54357822 FUNC(row_fdct)(data);
269
270 /* Pass 2: process columns.
271 * We remove the PASS1_BITS scaling, but leave the results scaled up
272 * by an overall factor of 8.
273 */
274
275 54357822 dataptr = data;
276
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 489220398 for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
277 434862576 tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7];
278 434862576 tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7];
279 434862576 tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6];
280 434862576 tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6];
281 434862576 tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5];
282 434862576 tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5];
283 434862576 tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4];
284 434862576 tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4];
285
286 /* Even part per LL&M figure 1 --- note that published figure is faulty;
287 * rotator "sqrt(2)*c1" should be "sqrt(2)*c6".
288 */
289
290 434862576 tmp10 = tmp0 + tmp3;
291 434862576 tmp13 = tmp0 - tmp3;
292 434862576 tmp11 = tmp1 + tmp2;
293 434862576 tmp12 = tmp1 - tmp2;
294
295 434862576 dataptr[DCTSIZE*0] = DESCALE(tmp10 + tmp11, OUT_SHIFT);
296 434862576 dataptr[DCTSIZE*4] = DESCALE(tmp10 - tmp11, OUT_SHIFT);
297
298 434862576 z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
299 434862576 dataptr[DCTSIZE*2] = DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
300 CONST_BITS + OUT_SHIFT);
301 434862576 dataptr[DCTSIZE*6] = DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
302 CONST_BITS + OUT_SHIFT);
303
304 /* Odd part per figure 8 --- note paper omits factor of sqrt(2).
305 * cK represents cos(K*pi/16).
306 * i0..i3 in the paper are tmp4..tmp7 here.
307 */
308
309 434862576 z1 = tmp4 + tmp7;
310 434862576 z2 = tmp5 + tmp6;
311 434862576 z3 = tmp4 + tmp6;
312 434862576 z4 = tmp5 + tmp7;
313 434862576 z5 = MULTIPLY(z3 + z4, FIX_1_175875602); /* sqrt(2) * c3 */
314
315 434862576 tmp4 = MULTIPLY(tmp4, FIX_0_298631336); /* sqrt(2) * (-c1+c3+c5-c7) */
316 434862576 tmp5 = MULTIPLY(tmp5, FIX_2_053119869); /* sqrt(2) * ( c1+c3-c5+c7) */
317 434862576 tmp6 = MULTIPLY(tmp6, FIX_3_072711026); /* sqrt(2) * ( c1+c3+c5-c7) */
318 434862576 tmp7 = MULTIPLY(tmp7, FIX_1_501321110); /* sqrt(2) * ( c1+c3-c5-c7) */
319 434862576 z1 = MULTIPLY(z1, - FIX_0_899976223); /* sqrt(2) * (c7-c3) */
320 434862576 z2 = MULTIPLY(z2, - FIX_2_562915447); /* sqrt(2) * (-c1-c3) */
321 434862576 z3 = MULTIPLY(z3, - FIX_1_961570560); /* sqrt(2) * (-c3-c5) */
322 434862576 z4 = MULTIPLY(z4, - FIX_0_390180644); /* sqrt(2) * (c5-c3) */
323
324 434862576 z3 += z5;
325 434862576 z4 += z5;
326
327 434862576 dataptr[DCTSIZE*7] = DESCALE(tmp4 + z1 + z3, CONST_BITS + OUT_SHIFT);
328 434862576 dataptr[DCTSIZE*5] = DESCALE(tmp5 + z2 + z4, CONST_BITS + OUT_SHIFT);
329 434862576 dataptr[DCTSIZE*3] = DESCALE(tmp6 + z2 + z3, CONST_BITS + OUT_SHIFT);
330 434862576 dataptr[DCTSIZE*1] = DESCALE(tmp7 + z1 + z4, CONST_BITS + OUT_SHIFT);
331
332 434862576 dataptr++; /* advance pointer to next column */
333 }
334 54357822 }
335
336 /*
337 * The secret of DCT2-4-8 is really simple -- you do the usual 1-DCT
338 * on the rows and then, instead of doing even and odd, part on the columns
339 * you do even part two times.
340 */
341 GLOBAL(void)
342 ✗ FUNC(ff_fdct248_islow)(int16_t *data)
343 {
344 int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7;
345 int tmp10, tmp11, tmp12, tmp13;
346 int z1;
347 int16_t *dataptr;
348 int ctr;
349
350 ✗ FUNC(row_fdct)(data);
351
352 /* Pass 2: process columns.
353 * We remove the PASS1_BITS scaling, but leave the results scaled up
354 * by an overall factor of 8.
355 */
356
357 ✗ dataptr = data;
358 ✗ for (ctr = DCTSIZE-1; ctr >= 0; ctr--) {
359 ✗ tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1];
360 ✗ tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3];
361 ✗ tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5];
362 ✗ tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7];
363 ✗ tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1];
364 ✗ tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3];
365 ✗ tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5];
366 ✗ tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7];
367
368 ✗ tmp10 = tmp0 + tmp3;
369 ✗ tmp11 = tmp1 + tmp2;
370 ✗ tmp12 = tmp1 - tmp2;
371 ✗ tmp13 = tmp0 - tmp3;
372
373 ✗ dataptr[DCTSIZE*0] = DESCALE(tmp10 + tmp11, OUT_SHIFT);
374 ✗ dataptr[DCTSIZE*4] = DESCALE(tmp10 - tmp11, OUT_SHIFT);
375
376 ✗ z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
377 ✗ dataptr[DCTSIZE*2] = DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
378 CONST_BITS+OUT_SHIFT);
379 ✗ dataptr[DCTSIZE*6] = DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
380 CONST_BITS+OUT_SHIFT);
381
382 ✗ tmp10 = tmp4 + tmp7;
383 ✗ tmp11 = tmp5 + tmp6;
384 ✗ tmp12 = tmp5 - tmp6;
385 ✗ tmp13 = tmp4 - tmp7;
386
387 ✗ dataptr[DCTSIZE*1] = DESCALE(tmp10 + tmp11, OUT_SHIFT);
388 ✗ dataptr[DCTSIZE*5] = DESCALE(tmp10 - tmp11, OUT_SHIFT);
389
390 ✗ z1 = MULTIPLY(tmp12 + tmp13, FIX_0_541196100);
391 ✗ dataptr[DCTSIZE*3] = DESCALE(z1 + MULTIPLY(tmp13, FIX_0_765366865),
392 CONST_BITS + OUT_SHIFT);
393 ✗ dataptr[DCTSIZE*7] = DESCALE(z1 + MULTIPLY(tmp12, - FIX_1_847759065),
394 CONST_BITS + OUT_SHIFT);
395
396 ✗ dataptr++; /* advance pointer to next column */
397 }
398 ✗ }
399