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
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,
48 * Scale MDCT coefficients from float to 24-bit fixed-point.
50 static void scale_coefficients(AC3EncodeContext *s)
52 int chan_size = AC3_MAX_COEFS * s->num_blocks;
54 s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
55 s->mdct_coef_buffer + (chan_size * !cpl),
56 chan_size * (s->channels + cpl));
61 * Clip MDCT coefficients to allowable range.
63 static void clip_coefficients(AudioDSPContext *adsp, float *coef,
66 adsp->vector_clipf(coef, coef, len, COEF_MIN, COEF_MAX);
71 * Calculate a single coupling coordinate.
73 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
77 coord *= sqrtf(energy_ch / energy_cpl);
78 return FFMIN(coord, COEF_MAX);
81 static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
82 const float *coef0, const float *coef1,
85 s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
89 #include "ac3enc_template.c"
93 * Finalize MDCT and free allocated memory.
95 * @param s AC-3 encoder private context
97 av_cold void ff_ac3_float_mdct_end(AC3EncodeContext *s)
99 ff_mdct_end(&s->mdct);
100 av_freep(&s->mdct_window);
105 * Initialize MDCT tables.
107 * @param s AC-3 encoder private context
108 * @return 0 on success, negative error code on failure
110 av_cold int ff_ac3_float_mdct_init(AC3EncodeContext *s)
118 window = av_malloc_array(n, sizeof(*window));
120 av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
121 return AVERROR(ENOMEM);
123 ff_kbd_window_init(window, 5.0, n2);
124 for (i = 0; i < n2; i++)
125 window[n-1-i] = window[i];
126 s->mdct_window = window;
128 return ff_mdct_init(&s->mdct, 9, 0, -2.0 / n);
132 av_cold int ff_ac3_float_encode_init(AVCodecContext *avctx)
134 AC3EncodeContext *s = avctx->priv_data;
135 s->fdsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
137 return AVERROR(ENOMEM);
138 return ff_ac3_encode_init(avctx);
141 AVCodec ff_ac3_encoder = {
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),
147 .init = ff_ac3_float_encode_init,
148 .encode2 = ff_ac3_float_encode_frame,
149 .close = ff_ac3_encode_close,
150 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
151 AV_SAMPLE_FMT_NONE },
152 .priv_class = &ac3enc_class,
153 .channel_layouts = ff_ac3_channel_layouts,
154 .defaults = ac3_defaults,