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 #define AC3ENC_TYPE AC3ENC_TYPE_AC3
37 #include "ac3enc_opts_template.c"
38 static const AVClass ac3enc_class = {
39 .class_name = "AC-3 Encoder",
40 .item_name = av_default_item_name,
41 .option = ac3_options,
42 .version = LIBAVUTIL_VERSION_INT,
45 #include "ac3enc_template.c"
49 * Finalize MDCT and free allocated memory.
51 * @param s AC-3 encoder private context
53 av_cold void ff_ac3_float_mdct_end(AC3EncodeContext *s)
55 ff_mdct_end(&s->mdct);
56 av_freep(&s->mdct_window);
61 * Initialize MDCT tables.
63 * @param s AC-3 encoder private context
64 * @return 0 on success, negative error code on failure
66 av_cold int ff_ac3_float_mdct_init(AC3EncodeContext *s)
74 window = av_malloc_array(n, sizeof(*window));
76 av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
77 return AVERROR(ENOMEM);
79 ff_kbd_window_init(window, 5.0, n2);
80 for (i = 0; i < n2; i++)
81 window[n-1-i] = window[i];
82 s->mdct_window = window;
84 return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
89 * Normalize the input samples.
90 * Not needed for the floating-point encoder.
92 static int normalize_samples(AC3EncodeContext *s)
99 * Scale MDCT coefficients from float to 24-bit fixed-point.
101 static void scale_coefficients(AC3EncodeContext *s)
103 int chan_size = AC3_MAX_COEFS * s->num_blocks;
105 s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
106 s->mdct_coef_buffer + (chan_size * !cpl),
107 chan_size * (s->channels + cpl));
110 static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
111 const float *coef0, const float *coef1,
114 s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
118 * Clip MDCT coefficients to allowable range.
120 static void clip_coefficients(DSPContext *dsp, float *coef, unsigned int len)
122 dsp->vector_clipf(coef, coef, COEF_MIN, COEF_MAX, len);
127 * Calculate a single coupling coordinate.
129 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
133 coord *= sqrtf(energy_ch / energy_cpl);
134 return FFMIN(coord, COEF_MAX);
138 AVCodec ff_ac3_encoder = {
140 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
141 .type = AVMEDIA_TYPE_AUDIO,
142 .id = AV_CODEC_ID_AC3,
143 .priv_data_size = sizeof(AC3EncodeContext),
144 .init = ff_ac3_encode_init,
145 .encode2 = ff_ac3_float_encode_frame,
146 .close = ff_ac3_encode_close,
147 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
148 AV_SAMPLE_FMT_NONE },
149 .priv_class = &ac3enc_class,
150 .channel_layouts = ff_ac3_channel_layouts,
151 .defaults = ac3_defaults,