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 AC3ENC_FLOAT 1
37 static const AVClass ac3enc_class = {
38 .class_name = "AC-3 Encoder",
39 .item_name = av_default_item_name,
40 .option = ff_ac3_enc_options,
41 .version = LIBAVUTIL_VERSION_INT,
46 * Scale MDCT coefficients from float to 24-bit fixed-point.
48 static void scale_coefficients(AC3EncodeContext *s)
50 int chan_size = AC3_MAX_COEFS * s->num_blocks;
52 s->ac3dsp.float_to_fixed24(s->fixed_coef_buffer + (chan_size * !cpl),
53 s->mdct_coef_buffer + (chan_size * !cpl),
54 chan_size * (s->channels + cpl));
59 * Clip MDCT coefficients to allowable range.
61 static void clip_coefficients(AudioDSPContext *adsp, float *coef,
64 adsp->vector_clipf(coef, coef, len, COEF_MIN, COEF_MAX);
69 * Calculate a single coupling coordinate.
71 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
75 coord *= sqrtf(energy_ch / energy_cpl);
76 return FFMIN(coord, COEF_MAX);
79 static void sum_square_butterfly(AC3EncodeContext *s, float sum[4],
80 const float *coef0, const float *coef1,
83 s->ac3dsp.sum_square_butterfly_float(sum, coef0, coef1, len);
87 #include "ac3enc_template.c"
91 * Finalize MDCT and free allocated memory.
93 * @param s AC-3 encoder private context
95 static av_cold void ac3_float_mdct_end(AC3EncodeContext *s)
97 ff_mdct_end(&s->mdct);
102 * Initialize MDCT tables.
104 * @param s AC-3 encoder private context
105 * @return 0 on success, negative error code on failure
107 static av_cold int ac3_float_mdct_init(AC3EncodeContext *s)
109 float *window = av_malloc_array(AC3_BLOCK_SIZE, sizeof(*window));
111 av_log(s->avctx, AV_LOG_ERROR, "Cannot allocate memory.\n");
112 return AVERROR(ENOMEM);
115 ff_kbd_window_init(window, 5.0, AC3_BLOCK_SIZE);
116 s->mdct_window = window;
118 return ff_mdct_init(&s->mdct, 9, 0, -2.0 / AC3_WINDOW_SIZE);
122 av_cold int ff_ac3_float_encode_init(AVCodecContext *avctx)
124 AC3EncodeContext *s = avctx->priv_data;
125 s->mdct_end = ac3_float_mdct_end;
126 s->mdct_init = ac3_float_mdct_init;
127 s->allocate_sample_buffers = allocate_sample_buffers;
128 s->fdsp = avpriv_float_dsp_alloc(avctx->flags & AV_CODEC_FLAG_BITEXACT);
130 return AVERROR(ENOMEM);
131 return ff_ac3_encode_init(avctx);
134 AVCodec ff_ac3_encoder = {
136 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
137 .type = AVMEDIA_TYPE_AUDIO,
138 .id = AV_CODEC_ID_AC3,
139 .priv_data_size = sizeof(AC3EncodeContext),
140 .init = ff_ac3_float_encode_init,
141 .encode2 = ff_ac3_float_encode_frame,
142 .close = ff_ac3_encode_close,
143 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_FLTP,
144 AV_SAMPLE_FMT_NONE },
145 .priv_class = &ac3enc_class,
146 .supported_samplerates = ff_ac3_sample_rate_tab,
147 .channel_layouts = ff_ac3_channel_layouts,
148 .defaults = ff_ac3_enc_defaults,
149 .caps_internal = FF_CODEC_CAP_INIT_THREADSAFE | FF_CODEC_CAP_INIT_CLEANUP,