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 Libav.
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.
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.
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
26 * fixed-point AC-3 encoder.
30 #undef CONFIG_AC3ENC_FLOAT
36 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
37 #include "ac3enc_opts_template.c"
38 static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
39 ac3_options, LIBAVUTIL_VERSION_INT };
41 #include "ac3enc_template.c"
45 * Finalize MDCT and free allocated memory.
47 * @param s AC-3 encoder private context
49 av_cold void AC3_NAME(mdct_end)(AC3EncodeContext *s)
51 ff_mdct_end(&s->mdct);
56 * Initialize MDCT tables.
58 * @param s AC-3 encoder private context
59 * @return 0 on success, negative error code on failure
61 av_cold int AC3_NAME(mdct_init)(AC3EncodeContext *s)
63 int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
64 s->mdct_window = ff_ac3_window;
70 * Normalize the input samples to use the maximum available precision.
71 * This assumes signed 16-bit input samples.
73 static int normalize_samples(AC3EncodeContext *s)
75 int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE);
78 s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
79 /* +6 to right-shift from 31-bit to 25-bit */
85 * Scale MDCT coefficients to 25-bit signed fixed-point.
87 static void scale_coefficients(AC3EncodeContext *s)
91 for (blk = 0; blk < s->num_blocks; blk++) {
92 AC3Block *block = &s->blocks[blk];
93 for (ch = 1; ch <= s->channels; ch++) {
94 s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
95 block->coeff_shift[ch]);
102 * Clip MDCT coefficients to allowable range.
104 static void clip_coefficients(AudioDSPContext *adsp, int32_t *coef,
107 adsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
112 * Calculate a single coupling coordinate.
114 static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
116 if (energy_cpl <= COEF_MAX) {
119 uint64_t coord = energy_ch / (energy_cpl >> 24);
120 uint32_t coord32 = FFMIN(coord, 1073741824);
121 coord32 = ff_sqrt(coord32) << 9;
122 return FFMIN(coord32, COEF_MAX);
127 static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
129 AC3EncodeContext *s = avctx->priv_data;
131 return ff_ac3_encode_init(avctx);
135 AVCodec ff_ac3_fixed_encoder = {
137 .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
138 .type = AVMEDIA_TYPE_AUDIO,
139 .id = AV_CODEC_ID_AC3,
140 .priv_data_size = sizeof(AC3EncodeContext),
141 .init = ac3_fixed_encode_init,
142 .encode2 = ff_ac3_fixed_encode_frame,
143 .close = ff_ac3_encode_close,
144 .sample_fmts = (const enum AVSampleFormat[]){ AV_SAMPLE_FMT_S16P,
145 AV_SAMPLE_FMT_NONE },
146 .priv_class = &ac3enc_class,
147 .channel_layouts = ff_ac3_channel_layouts,
148 .defaults = ac3_defaults,