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 * fixed-point AC-3 encoder.
30 #undef CONFIG_AC3ENC_FLOAT
36 #define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
37 #include "ac3enc_opts_template.c"
39 static const AVClass ac3enc_class
= {
40 .class_name
= "Fixed-Point AC-3 Encoder",
41 .item_name
= av_default_item_name
,
42 .option
= ac3_options
,
43 .version
= LIBAVUTIL_VERSION_INT
,
46 #include "ac3enc_template.c"
50 * Finalize MDCT and free allocated memory.
52 * @param s AC-3 encoder private context
54 av_cold
void AC3_NAME(mdct_end
)(AC3EncodeContext
*s
)
56 ff_mdct_end(&s
->mdct
);
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 AC3_NAME(mdct_init
)(AC3EncodeContext
*s
)
68 int ret
= ff_mdct_init(&s
->mdct
, 9, 0, -1.0);
69 s
->mdct_window
= ff_ac3_window
;
75 * Normalize the input samples to use the maximum available precision.
76 * This assumes signed 16-bit input samples.
78 static int normalize_samples(AC3EncodeContext
*s
)
80 int v
= s
->ac3dsp
.ac3_max_msb_abs_int16(s
->windowed_samples
, AC3_WINDOW_SIZE
);
83 s
->ac3dsp
.ac3_lshift_int16(s
->windowed_samples
, AC3_WINDOW_SIZE
, v
);
84 /* +6 to right-shift from 31-bit to 25-bit */
90 * Scale MDCT coefficients to 25-bit signed fixed-point.
92 static void scale_coefficients(AC3EncodeContext
*s
)
96 for (blk
= 0; blk
< s
->num_blocks
; blk
++) {
97 AC3Block
*block
= &s
->blocks
[blk
];
98 for (ch
= 1; ch
<= s
->channels
; ch
++) {
99 s
->ac3dsp
.ac3_rshift_int32(block
->mdct_coef
[ch
], AC3_MAX_COEFS
,
100 block
->coeff_shift
[ch
]);
105 static void sum_square_butterfly(AC3EncodeContext
*s
, int64_t sum
[4],
106 const int32_t *coef0
, const int32_t *coef1
,
109 s
->ac3dsp
.sum_square_butterfly_int32(sum
, coef0
, coef1
, len
);
113 * Clip MDCT coefficients to allowable range.
115 static void clip_coefficients(AudioDSPContext
*adsp
, int32_t *coef
,
118 adsp
->vector_clip_int32(coef
, coef
, COEF_MIN
, COEF_MAX
, len
);
123 * Calculate a single coupling coordinate.
125 static CoefType
calc_cpl_coord(CoefSumType energy_ch
, CoefSumType energy_cpl
)
127 if (energy_cpl
<= COEF_MAX
) {
130 uint64_t coord
= energy_ch
/ (energy_cpl
>> 24);
131 uint32_t coord32
= FFMIN(coord
, 1073741824);
132 coord32
= ff_sqrt(coord32
) << 9;
133 return FFMIN(coord32
, COEF_MAX
);
138 static av_cold
int ac3_fixed_encode_init(AVCodecContext
*avctx
)
140 AC3EncodeContext
*s
= avctx
->priv_data
;
142 return ff_ac3_encode_init(avctx
);
146 AVCodec ff_ac3_fixed_encoder
= {
148 .long_name
= NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
149 .type
= AVMEDIA_TYPE_AUDIO
,
150 .id
= AV_CODEC_ID_AC3
,
151 .priv_data_size
= sizeof(AC3EncodeContext
),
152 .init
= ac3_fixed_encode_init
,
153 .encode2
= ff_ac3_fixed_encode_frame
,
154 .close
= ff_ac3_encode_close
,
155 .sample_fmts
= (const enum AVSampleFormat
[]){ AV_SAMPLE_FMT_S16P
,
156 AV_SAMPLE_FMT_NONE
},
157 .priv_class
= &ac3enc_class
,
158 .channel_layouts
= ff_ac3_channel_layouts
,
159 .defaults
= ac3_defaults
,