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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 "ac3enc.h"
32 #include "eac3enc.h"
33 #include "kbdwin.h"
34 
35 
36 #if CONFIG_AC3_ENCODER
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 #endif
46 
47 #include "ac3enc_template.c"
48 
49 
50 /**
51  * Finalize MDCT and free allocated memory.
52  *
53  * @param s AC-3 encoder private context
54  */
56 {
57  ff_mdct_end(&s->mdct);
58  av_freep(&s->mdct_window);
59 }
60 
61 
62 /**
63  * Initialize MDCT tables.
64  *
65  * @param s AC-3 encoder private context
66  * @return 0 on success, negative error code on failure
67  */
69 {
70  float *window;
71  int i, n, n2;
72 
73  n = 1 << 9;
74  n2 = n >> 1;
75 
76  window = av_malloc(n * sizeof(*window));
77  if (!window) {
78  av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
79  return AVERROR(ENOMEM);
80  }
81  ff_kbd_window_init(window, 5.0, n2);
82  for (i = 0; i < n2; i++)
83  window[n-1-i] = window[i];
84  s->mdct_window = window;
85 
86  return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
87 }
88 
89 
90 /*
91  * Normalize the input samples.
92  * Not needed for the floating-point encoder.
93  */
95 {
96  return 0;
97 }
98 
99 
100 /*
101  * Scale MDCT coefficients from float to 24-bit fixed-point.
102  */
104 {
105  int chan_size = AC3_MAX_COEFS * s->num_blocks;
106  int cpl = s->cpl_on;
107  s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
108  s->mdct_coef_buffer + (chan_size * !cpl),
109  chan_size * (s->channels + cpl));
110 }
111 
112 static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
113  const float *coef0, const float *coef1,
114  int len)
115 {
116  s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
117 }
118 
119 /*
120  * Clip MDCT coefficients to allowable range.
121  */
122 static void clip_coefficients(DSPContext *dsp, float *coef, unsigned int len)
123 {
124  dsp->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 
139 
140 #if CONFIG_AC3_ENCODER
141 AVCodec ff_ac3_encoder = {
142  .name = "ac3",
143  .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
144  .type = AVMEDIA_TYPE_AUDIO,
145  .id = AV_CODEC_ID_AC3,
146  .priv_data_size = sizeof(AC3EncodeContext),
148  .encode2 = ff_ac3_float_encode_frame,
150  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
152  .priv_class = &ac3enc_class,
153  .channel_layouts = ff_ac3_channel_layouts,
154  .defaults = ac3_defaults,
155 };
156 #endif