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ac3enc_fixed.c
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1 /*
2  * The simplest AC-3 encoder
3  * Copyright (c) 2000 Fabrice Bellard
4  * Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
5  * Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
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 Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
24 /**
25  * @file
26  * fixed-point AC-3 encoder.
27  */
28 
29 #define CONFIG_FFT_FLOAT 0
30 #undef CONFIG_AC3ENC_FLOAT
31 #include "internal.h"
32 #include "ac3enc.h"
33 #include "eac3enc.h"
34 
35 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
36 #include "ac3enc_opts_template.c"
37 
38 static const AVClass ac3enc_class = {
39  .class_name = "Fixed-Point AC-3 Encoder",
40  .item_name = av_default_item_name,
41  .option = ac3_options,
42  .version = LIBAVUTIL_VERSION_INT,
43 };
44 
45 #include "ac3enc_template.c"
46 
47 
48 /**
49  * Finalize MDCT and free allocated memory.
50  *
51  * @param s AC-3 encoder private context
52  */
54 {
55  ff_mdct_end(&s->mdct);
56 }
57 
58 
59 /**
60  * Initialize MDCT tables.
61  *
62  * @param s AC-3 encoder private context
63  * @return 0 on success, negative error code on failure
64  */
66 {
67  int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
68  s->mdct_window = ff_ac3_window;
69  return ret;
70 }
71 
72 
73 /*
74  * Apply KBD window to input samples prior to MDCT.
75  */
76 static void apply_window(void *dsp, int16_t *output, const int16_t *input,
77  const int16_t *window, unsigned int len)
78 {
79  DSPContext *dsp0 = dsp;
80  dsp0->apply_window_int16(output, input, window, len);
81 }
82 
83 
84 /*
85  * Normalize the input samples to use the maximum available precision.
86  * This assumes signed 16-bit input samples.
87  */
89 {
91  v = 14 - av_log2(v);
92  if (v > 0)
94  /* +6 to right-shift from 31-bit to 25-bit */
95  return v + 6;
96 }
97 
98 
99 /*
100  * Scale MDCT coefficients to 25-bit signed fixed-point.
101  */
103 {
104  int blk, ch;
105 
106  for (blk = 0; blk < s->num_blocks; blk++) {
107  AC3Block *block = &s->blocks[blk];
108  for (ch = 1; ch <= s->channels; ch++) {
110  block->coeff_shift[ch]);
111  }
112  }
113 }
114 
115 static void sum_square_butterfly(AC3EncodeContext *s, int64_t sum[4],
116  const int32_t *coef0, const int32_t *coef1,
117  int len)
118 {
119  s->ac3dsp.sum_square_butterfly_int32(sum, coef0, coef1, len);
120 }
121 
122 /*
123  * Clip MDCT coefficients to allowable range.
124  */
125 static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
126 {
127  dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
128 }
129 
130 
131 /*
132  * Calculate a single coupling coordinate.
133  */
134 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
135 {
136  if (energy_cpl <= COEF_MAX) {
137  return 1048576;
138  } else {
139  uint64_t coord = energy_ch / (energy_cpl >> 24);
140  uint32_t coord32 = FFMIN(coord, 1073741824);
141  coord32 = ff_sqrt(coord32) << 9;
142  return FFMIN(coord32, COEF_MAX);
143  }
144 }
145 
146 
148 {
149  AC3EncodeContext *s = avctx->priv_data;
150  s->fixed_point = 1;
151  return ff_ac3_encode_init(avctx);
152 }
153 
154 
156  .name = "ac3_fixed",
157  .type = AVMEDIA_TYPE_AUDIO,
158  .id = AV_CODEC_ID_AC3,
159  .priv_data_size = sizeof(AC3EncodeContext),
161  .encode2 = ff_ac3_fixed_encode_frame,
163  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16P,
165  .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
166  .priv_class = &ac3enc_class,
167  .channel_layouts = ff_ac3_channel_layouts,
168  .defaults = ac3_defaults,
169 };