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 "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 = { "AC-3 Encoder", av_default_item_name,
41 #endif
42 
43 #include "ac3enc_template.c"
44 
45 
52 {
53  ff_mdct_end(&s->mdct);
54  av_freep(&s->mdct_window);
55 }
56 
57 
65 {
66  float *window;
67  int i, n, n2;
68 
69  n = 1 << 9;
70  n2 = n >> 1;
71 
72  window = av_malloc(n * sizeof(*window));
73  if (!window) {
74  av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
75  return AVERROR(ENOMEM);
76  }
77  ff_kbd_window_init(window, 5.0, n2);
78  for (i = 0; i < n2; i++)
79  window[n-1-i] = window[i];
80  s->mdct_window = window;
81 
82  return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
83 }
84 
85 
86 /*
87  * Apply KBD window to input samples prior to MDCT.
88  */
89 static void apply_window(void *dsp, float *output,
90  const float *input, const float *window,
91  unsigned int len)
92 {
94  fdsp->vector_fmul(output, input, window, len);
95 }
96 
97 
98 /*
99  * Normalize the input samples.
100  * Not needed for the floating-point encoder.
101  */
103 {
104  return 0;
105 }
106 
107 
108 /*
109  * Scale MDCT coefficients from float to 24-bit fixed-point.
110  */
112 {
113  int chan_size = AC3_MAX_COEFS * s->num_blocks;
114  int cpl = s->cpl_on;
115  s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
116  s->mdct_coef_buffer + (chan_size * !cpl),
117  chan_size * (s->channels + cpl));
118 }
119 
120 
121 /*
122  * Clip MDCT coefficients to allowable range.
123  */
124 static void clip_coefficients(DSPContext *dsp, float *coef, unsigned int len)
125 {
126  dsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
127 }
128 
129 
130 /*
131  * Calculate a single coupling coordinate.
132  */
133 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
134 {
135  float coord = 0.125;
136  if (energy_cpl > 0)
137  coord *= sqrtf(energy_ch / energy_cpl);
138  return FFMIN(coord, COEF_MAX);
139 }
140 
141 
142 #if CONFIG_AC3_ENCODER
143 AVCodec ff_ac3_encoder = {
144  .name = "ac3",
145  .type = AVMEDIA_TYPE_AUDIO,
146  .id = AV_CODEC_ID_AC3,
147  .priv_data_size = sizeof(AC3EncodeContext),
149  .encode2 = ff_ac3_float_encode_frame,
151  .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
153  .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
154  .priv_class = &ac3enc_class,
155  .channel_layouts = ff_ac3_channel_layouts,
156  .defaults = ac3_defaults,
157 };
158 #endif