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ac3enc_float.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  * floating-point AC-3 encoder.
27  */
28 
29 #define CONFIG_AC3ENC_FLOAT 1
30 #include "internal.h"
31 #include "audiodsp.h"
32 #include "ac3enc.h"
33 #include "eac3enc.h"
34 #include "kbdwin.h"
35 
36 
37 #define AC3ENC_TYPE AC3ENC_TYPE_AC3
38 #include "ac3enc_opts_template.c"
39 static const AVClass ac3enc_class = {
40  .class_name = "AC-3 Encoder",
41  .item_name = av_default_item_name,
42  .option = ac3_options,
43  .version = LIBAVUTIL_VERSION_INT,
44 };
45 
46 #include "ac3enc_template.c"
47 
48 
49 /**
50  * Finalize MDCT and free allocated memory.
51  *
52  * @param s AC-3 encoder private context
53  */
55 {
56  ff_mdct_end(&s->mdct);
57  av_freep(&s->mdct_window);
58 }
59 
60 
61 /**
62  * Initialize MDCT tables.
63  *
64  * @param s AC-3 encoder private context
65  * @return 0 on success, negative error code on failure
66  */
68 {
69  float *window;
70  int i, n, n2;
71 
72  n = 1 << 9;
73  n2 = n >> 1;
74 
75  window = av_malloc_array(n, sizeof(*window));
76  if (!window) {
77  av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
78  return AVERROR(ENOMEM);
79  }
80  ff_kbd_window_init(window, 5.0, n2);
81  for (i = 0; i < n2; i++)
82  window[n-1-i] = window[i];
83  s->mdct_window = window;
84 
85  return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
86 }
87 
88 
89 /*
90  * Normalize the input samples.
91  * Not needed for the floating-point encoder.
92  */
94 {
95  return 0;
96 }
97 
98 
99 /*
100  * Scale MDCT coefficients from float to 24-bit fixed-point.
101  */
103 {
104  int chan_size = AC3_MAX_COEFS * s->num_blocks;
105  int cpl = s->cpl_on;
106  s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
107  s->mdct_coef_buffer + (chan_size * !cpl),
108  chan_size * (s->channels + cpl));
109 }
110 
111 static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
112  const float *coef0, const float *coef1,
113  int len)
114 {
115  s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
116 }
117 
118 /*
119  * Clip MDCT coefficients to allowable range.
120  */
121 static void clip_coefficients(AudioDSPContext *adsp, float *coef,
122  unsigned int len)
123 {
124  adsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
125 }
126 
127 
128 /*
129  * Calculate a single coupling coordinate.
130  */
131 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
132 {
133  float coord = 0.125;
134  if (energy_cpl > 0)
135  coord *= sqrtf(energy_ch / energy_cpl);
136  return FFMIN(coord, COEF_MAX);
137 }
138 
140 {
141  AC3EncodeContext *s = avctx->priv_data;
143  return ff_ac3_encode_init(avctx);
144 }
145 
147  .name = "ac3",
148  .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
149  .type = AVMEDIA_TYPE_AUDIO,
150  .id = AV_CODEC_ID_AC3,
151  .priv_data_size = sizeof(AC3EncodeContext),
153  .encode2 = ff_ac3_float_encode_frame,
155  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
157  .priv_class = &ac3enc_class,
158  .channel_layouts = ff_ac3_channel_layouts,
159  .defaults = ac3_defaults,
160 };