FFmpeg coverage


Directory: ../../../ffmpeg/
File: src/libavcodec/dct.c
Date: 2021-09-26 18:22:30
Exec Total Coverage
Lines: 111 114 97.4%
Branches: 28 31 90.3%

Line Branch Exec Source
1 /*
2 * (I)DCT Transforms
3 * Copyright (c) 2009 Peter Ross <pross@xvid.org>
4 * Copyright (c) 2010 Alex Converse <alex.converse@gmail.com>
5 * Copyright (c) 2010 Vitor Sessak
6 *
7 * This file is part of FFmpeg.
8 *
9 * FFmpeg is free software; you can redistribute it and/or
10 * modify it under the terms of the GNU Lesser General Public
11 * License as published by the Free Software Foundation; either
12 * version 2.1 of the License, or (at your option) any later version.
13 *
14 * FFmpeg is distributed in the hope that it will be useful,
15 * but WITHOUT ANY WARRANTY; without even the implied warranty of
16 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
17 * Lesser General Public License for more details.
18 *
19 * You should have received a copy of the GNU Lesser General Public
20 * License along with FFmpeg; if not, write to the Free Software
21 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA
22 */
23
24 /**
25 * @file
26 * (Inverse) Discrete Cosine Transforms. These are also known as the
27 * type II and type III DCTs respectively.
28 */
29
30 #include <math.h>
31 #include <string.h>
32
33 #include "libavutil/mathematics.h"
34 #include "dct.h"
35 #include "dct32.h"
36
37 /* sin((M_PI * x / (2 * n)) */
38 #define SIN(s, n, x) (s->costab[(n) - (x)])
39
40 /* cos((M_PI * x / (2 * n)) */
41 #define COS(s, n, x) (s->costab[x])
42
43 5614 static void dst_calc_I_c(DCTContext *ctx, FFTSample *data)
44 {
45 5614 int n = 1 << ctx->nbits;
46 int i;
47
48 5614 data[0] = 0;
49
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179648 for (i = 1; i < n / 2; i++) {
50 174034 float tmp1 = data[i ];
51 174034 float tmp2 = data[n - i];
52 174034 float s = SIN(ctx, n, 2 * i);
53
54 174034 s *= tmp1 + tmp2;
55 174034 tmp1 = (tmp1 - tmp2) * 0.5f;
56 174034 data[i] = s + tmp1;
57 174034 data[n - i] = s - tmp1;
58 }
59
60 5614 data[n / 2] *= 2;
61 5614 ctx->rdft.rdft_calc(&ctx->rdft, data);
62
63 5614 data[0] *= 0.5f;
64
65
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179648 for (i = 1; i < n - 2; i += 2) {
66 174034 data[i + 1] += data[i - 1];
67 174034 data[i] = -data[i + 2];
68 }
69
70 5614 data[n - 1] = 0;
71 5614 }
72
73 5614 static void dct_calc_I_c(DCTContext *ctx, FFTSample *data)
74 {
75 5614 int n = 1 << ctx->nbits;
76 int i;
77 5614 float next = -0.5f * (data[0] - data[n]);
78
79
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185262 for (i = 0; i < n / 2; i++) {
80 179648 float tmp1 = data[i];
81 179648 float tmp2 = data[n - i];
82 179648 float s = SIN(ctx, n, 2 * i);
83 179648 float c = COS(ctx, n, 2 * i);
84
85 179648 c *= tmp1 - tmp2;
86 179648 s *= tmp1 - tmp2;
87
88 179648 next += c;
89
90 179648 tmp1 = (tmp1 + tmp2) * 0.5f;
91 179648 data[i] = tmp1 - s;
92 179648 data[n - i] = tmp1 + s;
93 }
94
95 5614 ctx->rdft.rdft_calc(&ctx->rdft, data);
96 5614 data[n] = data[1];
97 5614 data[1] = next;
98
99
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179648 for (i = 3; i <= n; i += 2)
100 174034 data[i] = data[i - 2] - data[i];
101 5614 }
102
103 256 static void dct_calc_III_c(DCTContext *ctx, FFTSample *data)
104 {
105 256 int n = 1 << ctx->nbits;
106 int i;
107
108 256 float next = data[n - 1];
109 256 float inv_n = 1.0f / n;
110
111
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130032 for (i = n - 2; i >= 2; i -= 2) {
112 129776 float val1 = data[i];
113 129776 float val2 = data[i - 1] - data[i + 1];
114 129776 float c = COS(ctx, n, i);
115 129776 float s = SIN(ctx, n, i);
116
117 129776 data[i] = c * val1 + s * val2;
118 129776 data[i + 1] = s * val1 - c * val2;
119 }
120
121 256 data[1] = 2 * next;
122
123 256 ctx->rdft.rdft_calc(&ctx->rdft, data);
124
125
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130288 for (i = 0; i < n / 2; i++) {
126 130032 float tmp1 = data[i] * inv_n;
127 130032 float tmp2 = data[n - i - 1] * inv_n;
128 130032 float csc = ctx->csc2[i] * (tmp1 - tmp2);
129
130 130032 tmp1 += tmp2;
131 130032 data[i] = tmp1 + csc;
132 130032 data[n - i - 1] = tmp1 - csc;
133 }
134 256 }
135
136 16 static void dct_calc_II_c(DCTContext *ctx, FFTSample *data)
137 {
138 16 int n = 1 << ctx->nbits;
139 int i;
140 float next;
141
142
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8160 for (i = 0; i < n / 2; i++) {
143 8144 float tmp1 = data[i];
144 8144 float tmp2 = data[n - i - 1];
145 8144 float s = SIN(ctx, n, 2 * i + 1);
146
147 8144 s *= tmp1 - tmp2;
148 8144 tmp1 = (tmp1 + tmp2) * 0.5f;
149
150 8144 data[i] = tmp1 + s;
151 8144 data[n-i-1] = tmp1 - s;
152 }
153
154 16 ctx->rdft.rdft_calc(&ctx->rdft, data);
155
156 16 next = data[1] * 0.5;
157 16 data[1] *= -1;
158
159
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8160 for (i = n - 2; i >= 0; i -= 2) {
160 8144 float inr = data[i ];
161 8144 float ini = data[i + 1];
162 8144 float c = COS(ctx, n, i);
163 8144 float s = SIN(ctx, n, i);
164
165 8144 data[i] = c * inr + s * ini;
166 8144 data[i + 1] = next;
167
168 8144 next += s * inr - c * ini;
169 }
170 16 }
171
172 2 static void dct32_func(DCTContext *ctx, FFTSample *data)
173 {
174 2 ctx->dct32(data, data);
175 2 }
176
177 210 av_cold int ff_dct_init(DCTContext *s, int nbits, enum DCTTransformType inverse)
178 {
179 210 int n = 1 << nbits;
180 int i;
181 int ret;
182
183 210 memset(s, 0, sizeof(*s));
184
185 210 s->nbits = nbits;
186 210 s->inverse = inverse;
187
188
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210 if (inverse == DCT_II && nbits == 5) {
189 156 s->dct_calc = dct32_func;
190 } else {
191 54 ff_init_ff_cos_tabs(nbits + 2);
192
193 54 s->costab = ff_cos_tabs[nbits + 2];
194 54 s->csc2 = av_malloc_array(n / 2, sizeof(FFTSample));
195
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54 if (!s->csc2)
196 return AVERROR(ENOMEM);
197
198
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54 if ((ret = ff_rdft_init(&s->rdft, nbits, inverse == DCT_III)) < 0) {
199 av_freep(&s->csc2);
200 return ret;
201 }
202
203
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19958 for (i = 0; i < n / 2; i++)
204 19904 s->csc2[i] = 0.5 / sin((M_PI / (2 * n) * (2 * i + 1)));
205
206
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54 switch (inverse) {
207 8 case DCT_I : s->dct_calc = dct_calc_I_c; break;
208 16 case DCT_II : s->dct_calc = dct_calc_II_c; break;
209 22 case DCT_III: s->dct_calc = dct_calc_III_c; break;
210 8 case DST_I : s->dct_calc = dst_calc_I_c; break;
211 }
212 }
213
214 210 s->dct32 = ff_dct32_float;
215 if (ARCH_X86)
216 210 ff_dct_init_x86(s);
217
218 210 return 0;
219 }
220
221 56 av_cold void ff_dct_end(DCTContext *s)
222 {
223 56 ff_rdft_end(&s->rdft);
224 56 av_freep(&s->csc2);
225 56 }
226