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>
7 * This file is part of FFmpeg.
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.
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.
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
26 * floating-point AC-3 encoder.
29 #define CONFIG_AC3ENC_FLOAT 1
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,
47 #include "ac3enc_template.c"
51 * Finalize MDCT and free allocated memory.
53 * @param s AC-3 encoder private context
55 av_cold void ff_ac3_float_mdct_end(AC3EncodeContext *s)
57 ff_mdct_end(&s->mdct);
58 av_freep(&s->mdct_window);
63 * Initialize MDCT tables.
65 * @param s AC-3 encoder private context
66 * @return 0 on success, negative error code on failure
68 av_cold int ff_ac3_float_mdct_init(AC3EncodeContext *s)
76 window = av_malloc(n * sizeof(*window));
78 av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
79 return AVERROR(ENOMEM);
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;
86 return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
91 * Apply KBD window to input samples prior to MDCT.
93 static void apply_window(void *dsp, float *output,
94 const float *input, const float *window,
97 AVFloatDSPContext *fdsp = dsp;
98 fdsp->vector_fmul(output, input, window, len);
103 * Normalize the input samples.
104 * Not needed for the floating-point encoder.
106 static int normalize_samples(AC3EncodeContext *s)
113 * Scale MDCT coefficients from float to 24-bit fixed-point.
115 static void scale_coefficients(AC3EncodeContext *s)
117 int chan_size = AC3_MAX_COEFS * s->num_blocks;
119 s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
120 s->mdct_coef_buffer + (chan_size * !cpl),
121 chan_size * (s->channels + cpl));
124 static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
125 const float *coef0, const float *coef1,
128 s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
132 * Clip MDCT coefficients to allowable range.
134 static void clip_coefficients(DSPContext *dsp, float *coef, unsigned int len)
136 dsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
141 * Calculate a single coupling coordinate.
143 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
147 coord *= sqrtf(energy_ch / energy_cpl);
148 return FFMIN(coord, COEF_MAX);
152 #if CONFIG_AC3_ENCODER
153 AVCodec ff_ac3_encoder = {
155 .type = AVMEDIA_TYPE_AUDIO,
156 .id = AV_CODEC_ID_AC3,
157 .priv_data_size = sizeof(AC3EncodeContext),
158 .init = ff_ac3_encode_init,
159 .encode2 = ff_ac3_float_encode_frame,
160 .close = ff_ac3_encode_close,
161 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLT,
162 AV_SAMPLE_FMT_NONE },
163 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
164 .priv_class = &ac3enc_class,
165 .channel_layouts = ff_ac3_channel_layouts,
166 .defaults = ac3_defaults,