1/*
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>
6 *
7 * This file is part of Libav.
8 *
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.
13 *
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.
18 *
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
22 */
23
24/**
25 * @file
26 * fixed-point AC-3 encoder.
27 */
28
29#define CONFIG_FFT_FLOAT 0
30#undef CONFIG_AC3ENC_FLOAT
31#include "ac3enc.h"
32#include "eac3enc.h"
33
34#define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
35#include "ac3enc_opts_template.c"
36static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
37                                      ac3fixed_options, LIBAVUTIL_VERSION_INT };
38
39#include "ac3enc_template.c"
40
41
42/**
43 * Finalize MDCT and free allocated memory.
44 *
45 * @param s  AC-3 encoder private context
46 */
47av_cold void AC3_NAME(mdct_end)(AC3EncodeContext *s)
48{
49    ff_mdct_end(&s->mdct);
50}
51
52
53/**
54 * Initialize MDCT tables.
55 *
56 * @param s  AC-3 encoder private context
57 * @return   0 on success, negative error code on failure
58 */
59av_cold int AC3_NAME(mdct_init)(AC3EncodeContext *s)
60{
61    int ret = ff_mdct_init(&s->mdct, 9, 0, -1.0);
62    s->mdct_window = ff_ac3_window;
63    return ret;
64}
65
66
67/*
68 * Apply KBD window to input samples prior to MDCT.
69 */
70static void apply_window(DSPContext *dsp, int16_t *output, const int16_t *input,
71                         const int16_t *window, unsigned int len)
72{
73    dsp->apply_window_int16(output, input, window, len);
74}
75
76
77/*
78 * Normalize the input samples to use the maximum available precision.
79 * This assumes signed 16-bit input samples.
80 */
81static int normalize_samples(AC3EncodeContext *s)
82{
83    int v = s->ac3dsp.ac3_max_msb_abs_int16(s->windowed_samples, AC3_WINDOW_SIZE);
84    v = 14 - av_log2(v);
85    if (v > 0)
86        s->ac3dsp.ac3_lshift_int16(s->windowed_samples, AC3_WINDOW_SIZE, v);
87    /* +6 to right-shift from 31-bit to 25-bit */
88    return v + 6;
89}
90
91
92/*
93 * Scale MDCT coefficients to 25-bit signed fixed-point.
94 */
95static void scale_coefficients(AC3EncodeContext *s)
96{
97    int blk, ch;
98
99    for (blk = 0; blk < s->num_blocks; blk++) {
100        AC3Block *block = &s->blocks[blk];
101        for (ch = 1; ch <= s->channels; ch++) {
102            s->ac3dsp.ac3_rshift_int32(block->mdct_coef[ch], AC3_MAX_COEFS,
103                                       block->coeff_shift[ch]);
104        }
105    }
106}
107
108
109/*
110 * Clip MDCT coefficients to allowable range.
111 */
112static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
113{
114    dsp->vector_clip_int32(coef, coef, COEF_MIN, COEF_MAX, len);
115}
116
117
118/*
119 * Calculate a single coupling coordinate.
120 */
121static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
122{
123    if (energy_cpl <= COEF_MAX) {
124        return 1048576;
125    } else {
126        uint64_t coord   = energy_ch / (energy_cpl >> 24);
127        uint32_t coord32 = FFMIN(coord, 1073741824);
128        coord32          = ff_sqrt(coord32) << 9;
129        return FFMIN(coord32, COEF_MAX);
130    }
131}
132
133
134static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
135{
136    AC3EncodeContext *s = avctx->priv_data;
137    s->fixed_point = 1;
138    return ff_ac3_encode_init(avctx);
139}
140
141
142AVCodec ff_ac3_fixed_encoder = {
143    .name           = "ac3_fixed",
144    .type           = AVMEDIA_TYPE_AUDIO,
145    .id             = CODEC_ID_AC3,
146    .priv_data_size = sizeof(AC3EncodeContext),
147    .init           = ac3_fixed_encode_init,
148    .encode         = ff_ac3_fixed_encode_frame,
149    .close          = ff_ac3_encode_close,
150    .sample_fmts = (const enum AVSampleFormat[]){AV_SAMPLE_FMT_S16,AV_SAMPLE_FMT_NONE},
151    .long_name = NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
152    .priv_class = &ac3enc_class,
153    .channel_layouts = ff_ac3_channel_layouts,
154};
155