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 Libav.
8  *
9  * Libav 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  * Libav 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 Libav; if not, write to the Free Software
21  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22  */
23 
29 #define CONFIG_AC3ENC_FLOAT 1
30 #include "ac3enc.h"
31 #include "eac3enc.h"
32 #include "kbdwin.h"
33 
34 
35 #if CONFIG_AC3_ENCODER
36 #define AC3ENC_TYPE AC3ENC_TYPE_AC3
37 #include "ac3enc_opts_template.c"
38 static const AVClass ac3enc_class = { "AC-3 Encoder", av_default_item_name,
39  ac3_options, LIBAVUTIL_VERSION_INT };
40 #endif
41 
42 #include "ac3enc_template.c"
43 
44 
51 {
52  ff_mdct_end(&s->mdct);
53  av_freep(&s->mdct_window);
54 }
55 
56 
64 {
65  float *window;
66  int i, n, n2;
67 
68  n = 1 << 9;
69  n2 = n >> 1;
70 
71  window = av_malloc(n * sizeof(*window));
72  if (!window) {
73  av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
74  return AVERROR(ENOMEM);
75  }
76  ff_kbd_window_init(window, 5.0, n2);
77  for (i = 0; i < n2; i++)
78  window[n-1-i] = window[i];
79  s->mdct_window = window;
80 
81  return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
82 }
83 
84 
85 /*
86  * Apply KBD window to input samples prior to MDCT.
87  */
88 static void apply_window(DSPContext *dsp, float *output, const float *input,
89  const float *window, unsigned int len)
90 {
91  dsp->vector_fmul(output, input, window, len);
92 }
93 
94 
95 /*
96  * Normalize the input samples.
97  * Not needed for the floating-point encoder.
98  */
100 {
101  return 0;
102 }
103 
104 
105 /*
106  * Scale MDCT coefficients from float to 24-bit fixed-point.
107  */
109 {
110  int chan_size = AC3_MAX_COEFS * s->num_blocks;
111  int cpl = s->cpl_on;
112  s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
113  s->mdct_coef_buffer + (chan_size * !cpl),
114  chan_size * (s->channels + cpl));
115 }
116 
117 
118 /*
119  * Clip MDCT coefficients to allowable range.
120  */
121 static void clip_coefficients(DSPContext *dsp, float *coef, unsigned int len)
122 {
123  dsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
124 }
125 
126 
127 /*
128  * Calculate a single coupling coordinate.
129  */
130 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
131 {
132  float coord = 0.125;
133  if (energy_cpl > 0)
134  coord *= sqrtf(energy_ch / energy_cpl);
135  return FFMIN(coord, COEF_MAX);
136 }
137 
138 
139 #if CONFIG_AC3_ENCODER
140 AVCodec ff_ac3_encoder = {
141  .name = "ac3",
142  .type = AVMEDIA_TYPE_AUDIO,
143  .id = CODEC_ID_AC3,
144  .priv_data_size = sizeof(AC3EncodeContext),
146  .encode = ff_ac3_float_encode_frame,
148  .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_FLT,AV_SAMPLE_FMT_NONE},
149  .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
150  .priv_class = &ac3enc_class,
151  .channel_layouts = ff_ac3_channel_layouts,
152 };
153 #endif