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
,
46 #include "ac3enc_template.c"
50 * Finalize MDCT and free allocated memory.
52 * @param s AC-3 encoder private context
54 av_cold
void ff_ac3_float_mdct_end(AC3EncodeContext
*s
)
56 ff_mdct_end(&s
->mdct
);
57 av_freep(&s
->mdct_window
);
62 * Initialize MDCT tables.
64 * @param s AC-3 encoder private context
65 * @return 0 on success, negative error code on failure
67 av_cold
int ff_ac3_float_mdct_init(AC3EncodeContext
*s
)
75 window
= av_malloc_array(n
, sizeof(*window
));
77 av_log(s
->avctx
, AV_LOG_ERROR
, "Cannot allocate memory.\n");
78 return AVERROR(ENOMEM
);
80 ff_kbd_window_init(window
, 5.0, n2
);
81 for (i
= 0; i
< n2
; i
++)
82 window
[n
-1-i
] = window
[i
];
83 s
->mdct_window
= window
;
85 return ff_mdct_init(&s
->mdct
, 9, 0, -2.0 / n
);
90 * Normalize the input samples.
91 * Not needed for the floating-point encoder.
93 static int normalize_samples(AC3EncodeContext
*s
)
100 * Scale MDCT coefficients from float to 24-bit fixed-point.
102 static void scale_coefficients(AC3EncodeContext
*s
)
104 int chan_size
= AC3_MAX_COEFS
* s
->num_blocks
;
106 s
->ac3dsp
.float_to_fixed24(s
->fixed_coef_buffer
+ (chan_size
* !cpl
),
107 s
->mdct_coef_buffer
+ (chan_size
* !cpl
),
108 chan_size
* (s
->channels
+ cpl
));
111 static void sum_square_butterfly(AC3EncodeContext
*s
, float sum
[4],
112 const float *coef0
, const float *coef1
,
115 s
->ac3dsp
.sum_square_butterfly_float(sum
, coef0
, coef1
, len
);
119 * Clip MDCT coefficients to allowable range.
121 static void clip_coefficients(AudioDSPContext
*adsp
, float *coef
,
124 adsp
->vector_clipf(coef
, coef
, COEF_MIN
, COEF_MAX
, len
);
129 * Calculate a single coupling coordinate.
131 static CoefType
calc_cpl_coord(CoefSumType energy_ch
, CoefSumType energy_cpl
)
135 coord
*= sqrtf(energy_ch
/ energy_cpl
);
136 return FFMIN(coord
, COEF_MAX
);
139 av_cold
int ff_ac3_float_encode_init(AVCodecContext
*avctx
)
141 AC3EncodeContext
*s
= avctx
->priv_data
;
142 s
->fdsp
= avpriv_float_dsp_alloc(avctx
->flags
& CODEC_FLAG_BITEXACT
);
144 return AVERROR(ENOMEM
);
145 return ff_ac3_encode_init(avctx
);
148 AVCodec ff_ac3_encoder
= {
150 .long_name
= NULL_IF_CONFIG_SMALL("ATSC A/52A (AC-3)"),
151 .type
= AVMEDIA_TYPE_AUDIO
,
152 .id
= AV_CODEC_ID_AC3
,
153 .priv_data_size
= sizeof(AC3EncodeContext
),
154 .init
= ff_ac3_float_encode_init
,
155 .encode2
= ff_ac3_float_encode_frame
,
156 .close
= ff_ac3_encode_close
,
157 .sample_fmts
= (const enum AVSampleFormat
[]){ AV_SAMPLE_FMT_FLTP
,
158 AV_SAMPLE_FMT_NONE
},
159 .priv_class
= &ac3enc_class
,
160 .channel_layouts
= ff_ac3_channel_layouts
,
161 .defaults
= ac3_defaults
,