blob: bbcf5984901c89798e213eba631f16c11ed6d677
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) 1994-1996, 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 fast, not so 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 Arai, Agui, and Nakajima's algorithm for |
47 | * scaled DCT. Their original paper (Trans. IEICE E-71(11):1095) is in |
48 | * Japanese, but the algorithm is described in the Pennebaker & Mitchell |
49 | * JPEG textbook (see REFERENCES section in file README). The following code |
50 | * is based directly on figure 4-8 in P&M. |
51 | * While an 8-point DCT cannot be done in less than 11 multiplies, it is |
52 | * possible to arrange the computation so that many of the multiplies are |
53 | * simple scalings of the final outputs. These multiplies can then be |
54 | * folded into the multiplications or divisions by the JPEG quantization |
55 | * table entries. The AA&N method leaves only 5 multiplies and 29 adds |
56 | * to be done in the DCT itself. |
57 | * The primary disadvantage of this method is that with fixed-point math, |
58 | * accuracy is lost due to imprecise representation of the scaled |
59 | * quantization values. The smaller the quantization table entry, the less |
60 | * precise the scaled value, so this implementation does worse with high- |
61 | * quality-setting files than with low-quality ones. |
62 | */ |
63 | |
64 | /** |
65 | * @file |
66 | * Independent JPEG Group's fast AAN dct. |
67 | */ |
68 | |
69 | #include <stdlib.h> |
70 | #include <stdio.h> |
71 | #include "libavutil/common.h" |
72 | #include "dct.h" |
73 | |
74 | #define DCTSIZE 8 |
75 | #define GLOBAL(x) x |
76 | #define RIGHT_SHIFT(x, n) ((x) >> (n)) |
77 | |
78 | /* |
79 | * This module is specialized to the case DCTSIZE = 8. |
80 | */ |
81 | |
82 | #if DCTSIZE != 8 |
83 | Sorry, this code only copes with 8x8 DCTs. /* deliberate syntax err */ |
84 | #endif |
85 | |
86 | |
87 | /* Scaling decisions are generally the same as in the LL&M algorithm; |
88 | * see jfdctint.c for more details. However, we choose to descale |
89 | * (right shift) multiplication products as soon as they are formed, |
90 | * rather than carrying additional fractional bits into subsequent additions. |
91 | * This compromises accuracy slightly, but it lets us save a few shifts. |
92 | * More importantly, 16-bit arithmetic is then adequate (for 8-bit samples) |
93 | * everywhere except in the multiplications proper; this saves a good deal |
94 | * of work on 16-bit-int machines. |
95 | * |
96 | * Again to save a few shifts, the intermediate results between pass 1 and |
97 | * pass 2 are not upscaled, but are represented only to integral precision. |
98 | * |
99 | * A final compromise is to represent the multiplicative constants to only |
100 | * 8 fractional bits, rather than 13. This saves some shifting work on some |
101 | * machines, and may also reduce the cost of multiplication (since there |
102 | * are fewer one-bits in the constants). |
103 | */ |
104 | |
105 | #define CONST_BITS 8 |
106 | |
107 | |
108 | /* Some C compilers fail to reduce "FIX(constant)" at compile time, thus |
109 | * causing a lot of useless floating-point operations at run time. |
110 | * To get around this we use the following pre-calculated constants. |
111 | * If you change CONST_BITS you may want to add appropriate values. |
112 | * (With a reasonable C compiler, you can just rely on the FIX() macro...) |
113 | */ |
114 | |
115 | #if CONST_BITS == 8 |
116 | #define FIX_0_382683433 ((int32_t) 98) /* FIX(0.382683433) */ |
117 | #define FIX_0_541196100 ((int32_t) 139) /* FIX(0.541196100) */ |
118 | #define FIX_0_707106781 ((int32_t) 181) /* FIX(0.707106781) */ |
119 | #define FIX_1_306562965 ((int32_t) 334) /* FIX(1.306562965) */ |
120 | #else |
121 | #define FIX_0_382683433 FIX(0.382683433) |
122 | #define FIX_0_541196100 FIX(0.541196100) |
123 | #define FIX_0_707106781 FIX(0.707106781) |
124 | #define FIX_1_306562965 FIX(1.306562965) |
125 | #endif |
126 | |
127 | |
128 | /* We can gain a little more speed, with a further compromise in accuracy, |
129 | * by omitting the addition in a descaling shift. This yields an incorrectly |
130 | * rounded result half the time... |
131 | */ |
132 | |
133 | #ifndef USE_ACCURATE_ROUNDING |
134 | #undef DESCALE |
135 | #define DESCALE(x,n) RIGHT_SHIFT(x, n) |
136 | #endif |
137 | |
138 | |
139 | /* Multiply a int16_t variable by an int32_t constant, and immediately |
140 | * descale to yield a int16_t result. |
141 | */ |
142 | |
143 | #define MULTIPLY(var,const) ((int16_t) DESCALE((var) * (const), CONST_BITS)) |
144 | |
145 | static av_always_inline void row_fdct(int16_t * data){ |
146 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
147 | int tmp10, tmp11, tmp12, tmp13; |
148 | int z1, z2, z3, z4, z5, z11, z13; |
149 | int16_t *dataptr; |
150 | int ctr; |
151 | |
152 | /* Pass 1: process rows. */ |
153 | |
154 | dataptr = data; |
155 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
156 | tmp0 = dataptr[0] + dataptr[7]; |
157 | tmp7 = dataptr[0] - dataptr[7]; |
158 | tmp1 = dataptr[1] + dataptr[6]; |
159 | tmp6 = dataptr[1] - dataptr[6]; |
160 | tmp2 = dataptr[2] + dataptr[5]; |
161 | tmp5 = dataptr[2] - dataptr[5]; |
162 | tmp3 = dataptr[3] + dataptr[4]; |
163 | tmp4 = dataptr[3] - dataptr[4]; |
164 | |
165 | /* Even part */ |
166 | |
167 | tmp10 = tmp0 + tmp3; /* phase 2 */ |
168 | tmp13 = tmp0 - tmp3; |
169 | tmp11 = tmp1 + tmp2; |
170 | tmp12 = tmp1 - tmp2; |
171 | |
172 | dataptr[0] = tmp10 + tmp11; /* phase 3 */ |
173 | dataptr[4] = tmp10 - tmp11; |
174 | |
175 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
176 | dataptr[2] = tmp13 + z1; /* phase 5 */ |
177 | dataptr[6] = tmp13 - z1; |
178 | |
179 | /* Odd part */ |
180 | |
181 | tmp10 = tmp4 + tmp5; /* phase 2 */ |
182 | tmp11 = tmp5 + tmp6; |
183 | tmp12 = tmp6 + tmp7; |
184 | |
185 | /* The rotator is modified from fig 4-8 to avoid extra negations. */ |
186 | z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
187 | z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
188 | z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
189 | z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
190 | |
191 | z11 = tmp7 + z3; /* phase 5 */ |
192 | z13 = tmp7 - z3; |
193 | |
194 | dataptr[5] = z13 + z2; /* phase 6 */ |
195 | dataptr[3] = z13 - z2; |
196 | dataptr[1] = z11 + z4; |
197 | dataptr[7] = z11 - z4; |
198 | |
199 | dataptr += DCTSIZE; /* advance pointer to next row */ |
200 | } |
201 | } |
202 | |
203 | /* |
204 | * Perform the forward DCT on one block of samples. |
205 | */ |
206 | |
207 | GLOBAL(void) |
208 | ff_fdct_ifast (int16_t * data) |
209 | { |
210 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
211 | int tmp10, tmp11, tmp12, tmp13; |
212 | int z1, z2, z3, z4, z5, z11, z13; |
213 | int16_t *dataptr; |
214 | int ctr; |
215 | |
216 | row_fdct(data); |
217 | |
218 | /* Pass 2: process columns. */ |
219 | |
220 | dataptr = data; |
221 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
222 | tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*7]; |
223 | tmp7 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*7]; |
224 | tmp1 = dataptr[DCTSIZE*1] + dataptr[DCTSIZE*6]; |
225 | tmp6 = dataptr[DCTSIZE*1] - dataptr[DCTSIZE*6]; |
226 | tmp2 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*5]; |
227 | tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*5]; |
228 | tmp3 = dataptr[DCTSIZE*3] + dataptr[DCTSIZE*4]; |
229 | tmp4 = dataptr[DCTSIZE*3] - dataptr[DCTSIZE*4]; |
230 | |
231 | /* Even part */ |
232 | |
233 | tmp10 = tmp0 + tmp3; /* phase 2 */ |
234 | tmp13 = tmp0 - tmp3; |
235 | tmp11 = tmp1 + tmp2; |
236 | tmp12 = tmp1 - tmp2; |
237 | |
238 | dataptr[DCTSIZE*0] = tmp10 + tmp11; /* phase 3 */ |
239 | dataptr[DCTSIZE*4] = tmp10 - tmp11; |
240 | |
241 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); /* c4 */ |
242 | dataptr[DCTSIZE*2] = tmp13 + z1; /* phase 5 */ |
243 | dataptr[DCTSIZE*6] = tmp13 - z1; |
244 | |
245 | /* Odd part */ |
246 | |
247 | tmp10 = tmp4 + tmp5; /* phase 2 */ |
248 | tmp11 = tmp5 + tmp6; |
249 | tmp12 = tmp6 + tmp7; |
250 | |
251 | /* The rotator is modified from fig 4-8 to avoid extra negations. */ |
252 | z5 = MULTIPLY(tmp10 - tmp12, FIX_0_382683433); /* c6 */ |
253 | z2 = MULTIPLY(tmp10, FIX_0_541196100) + z5; /* c2-c6 */ |
254 | z4 = MULTIPLY(tmp12, FIX_1_306562965) + z5; /* c2+c6 */ |
255 | z3 = MULTIPLY(tmp11, FIX_0_707106781); /* c4 */ |
256 | |
257 | z11 = tmp7 + z3; /* phase 5 */ |
258 | z13 = tmp7 - z3; |
259 | |
260 | dataptr[DCTSIZE*5] = z13 + z2; /* phase 6 */ |
261 | dataptr[DCTSIZE*3] = z13 - z2; |
262 | dataptr[DCTSIZE*1] = z11 + z4; |
263 | dataptr[DCTSIZE*7] = z11 - z4; |
264 | |
265 | dataptr++; /* advance pointer to next column */ |
266 | } |
267 | } |
268 | |
269 | /* |
270 | * Perform the forward 2-4-8 DCT on one block of samples. |
271 | */ |
272 | |
273 | GLOBAL(void) |
274 | ff_fdct_ifast248 (int16_t * data) |
275 | { |
276 | int tmp0, tmp1, tmp2, tmp3, tmp4, tmp5, tmp6, tmp7; |
277 | int tmp10, tmp11, tmp12, tmp13; |
278 | int z1; |
279 | int16_t *dataptr; |
280 | int ctr; |
281 | |
282 | row_fdct(data); |
283 | |
284 | /* Pass 2: process columns. */ |
285 | |
286 | dataptr = data; |
287 | for (ctr = DCTSIZE-1; ctr >= 0; ctr--) { |
288 | tmp0 = dataptr[DCTSIZE*0] + dataptr[DCTSIZE*1]; |
289 | tmp1 = dataptr[DCTSIZE*2] + dataptr[DCTSIZE*3]; |
290 | tmp2 = dataptr[DCTSIZE*4] + dataptr[DCTSIZE*5]; |
291 | tmp3 = dataptr[DCTSIZE*6] + dataptr[DCTSIZE*7]; |
292 | tmp4 = dataptr[DCTSIZE*0] - dataptr[DCTSIZE*1]; |
293 | tmp5 = dataptr[DCTSIZE*2] - dataptr[DCTSIZE*3]; |
294 | tmp6 = dataptr[DCTSIZE*4] - dataptr[DCTSIZE*5]; |
295 | tmp7 = dataptr[DCTSIZE*6] - dataptr[DCTSIZE*7]; |
296 | |
297 | /* Even part */ |
298 | |
299 | tmp10 = tmp0 + tmp3; |
300 | tmp11 = tmp1 + tmp2; |
301 | tmp12 = tmp1 - tmp2; |
302 | tmp13 = tmp0 - tmp3; |
303 | |
304 | dataptr[DCTSIZE*0] = tmp10 + tmp11; |
305 | dataptr[DCTSIZE*4] = tmp10 - tmp11; |
306 | |
307 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
308 | dataptr[DCTSIZE*2] = tmp13 + z1; |
309 | dataptr[DCTSIZE*6] = tmp13 - z1; |
310 | |
311 | tmp10 = tmp4 + tmp7; |
312 | tmp11 = tmp5 + tmp6; |
313 | tmp12 = tmp5 - tmp6; |
314 | tmp13 = tmp4 - tmp7; |
315 | |
316 | dataptr[DCTSIZE*1] = tmp10 + tmp11; |
317 | dataptr[DCTSIZE*5] = tmp10 - tmp11; |
318 | |
319 | z1 = MULTIPLY(tmp12 + tmp13, FIX_0_707106781); |
320 | dataptr[DCTSIZE*3] = tmp13 + z1; |
321 | dataptr[DCTSIZE*7] = tmp13 - z1; |
322 | |
323 | dataptr++; /* advance pointer to next column */ |
324 | } |
325 | } |
326 | |
327 | |
328 | #undef GLOBAL |
329 | #undef CONST_BITS |
330 | #undef DESCALE |
331 | #undef FIX_0_541196100 |
332 | #undef FIX_1_306562965 |
333 |