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libavcodec
ac3enc_fixed.c
Go to the documentation of this file.
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/*
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* The simplest AC-3 encoder
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* Copyright (c) 2000 Fabrice Bellard
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* Copyright (c) 2006-2010 Justin Ruggles <justin.ruggles@gmail.com>
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* Copyright (c) 2006-2010 Prakash Punnoor <prakash@punnoor.de>
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*
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* This file is part of Libav.
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*
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* Libav is free software; you can redistribute it and/or
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* modify it under the terms of the GNU Lesser General Public
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* License as published by the Free Software Foundation; either
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* version 2.1 of the License, or (at your option) any later version.
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*
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* Libav is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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* Lesser General Public License for more details.
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*
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* You should have received a copy of the GNU Lesser General Public
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* License along with Libav; if not, write to the Free Software
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* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
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*/
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#define CONFIG_FFT_FLOAT 0
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#undef CONFIG_AC3ENC_FLOAT
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#include "
ac3enc.h
"
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#include "
eac3enc.h
"
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#define AC3ENC_TYPE AC3ENC_TYPE_AC3_FIXED
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#include "
ac3enc_opts_template.c
"
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static
const
AVClass
ac3enc_class
= {
"Fixed-Point AC-3 Encoder"
,
av_default_item_name
,
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ac3fixed_options
,
LIBAVUTIL_VERSION_INT
};
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#include "
ac3enc_template.c
"
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av_cold
void
AC3_NAME
(
mdct_end
)(
AC3EncodeContext
*s)
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{
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ff_mdct_end
(&s->mdct);
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}
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av_cold
int
AC3_NAME
(
mdct_init
)(
AC3EncodeContext
*s)
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{
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int
ret =
ff_mdct_init
(&s->mdct, 9, 0, -1.0);
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s->mdct_window =
ff_ac3_window
;
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return
ret;
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}
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/*
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* Apply KBD window to input samples prior to MDCT.
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*/
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static
void
apply_window
(
DSPContext
*
dsp
, int16_t *output,
const
int16_t *input,
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const
int16_t *window,
unsigned
int
len
)
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{
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dsp->
apply_window_int16
(output, input, window, len);
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}
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/*
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* Normalize the input samples to use the maximum available precision.
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* This assumes signed 16-bit input samples.
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*/
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static
int
normalize_samples
(
AC3EncodeContext
*s)
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{
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int
v
= s->
ac3dsp
.
ac3_max_msb_abs_int16
(s->
windowed_samples
,
AC3_WINDOW_SIZE
);
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v = 14 - av_log2(v);
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if
(v > 0)
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s->
ac3dsp
.
ac3_lshift_int16
(s->
windowed_samples
,
AC3_WINDOW_SIZE
, v);
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/* +6 to right-shift from 31-bit to 25-bit */
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return
v + 6;
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}
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/*
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* Scale MDCT coefficients to 25-bit signed fixed-point.
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*/
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static
void
scale_coefficients
(
AC3EncodeContext
*s)
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{
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int
blk
, ch;
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for
(blk = 0; blk < s->
num_blocks
; blk++) {
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AC3Block
*
block
= &s->
blocks
[
blk
];
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for
(ch = 1; ch <= s->
channels
; ch++) {
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s->
ac3dsp
.
ac3_rshift_int32
(block->
mdct_coef
[ch],
AC3_MAX_COEFS
,
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block->
coeff_shift
[ch]);
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}
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}
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}
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/*
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* Clip MDCT coefficients to allowable range.
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*/
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static
void
clip_coefficients
(
DSPContext
*
dsp
, int32_t *coef,
unsigned
int
len
)
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{
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dsp->
vector_clip_int32
(coef, coef,
COEF_MIN
,
COEF_MAX
, len);
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}
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/*
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* Calculate a single coupling coordinate.
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*/
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static
CoefType
calc_cpl_coord
(
CoefSumType
energy_ch,
CoefSumType
energy_cpl)
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{
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if
(energy_cpl <=
COEF_MAX
) {
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return
1048576;
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}
else
{
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uint64_t coord = energy_ch / (energy_cpl >> 24);
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uint32_t coord32 =
FFMIN
(coord, 1073741824);
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coord32 =
ff_sqrt
(coord32) << 9;
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return
FFMIN
(coord32,
COEF_MAX
);
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}
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}
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static
av_cold
int
ac3_fixed_encode_init
(
AVCodecContext
*
avctx
)
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{
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AC3EncodeContext
*s = avctx->
priv_data
;
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s->
fixed_point
= 1;
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return
ff_ac3_encode_init
(avctx);
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}
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AVCodec
ff_ac3_fixed_encoder
= {
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.
name
=
"ac3_fixed"
,
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.type =
AVMEDIA_TYPE_AUDIO
,
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.id =
CODEC_ID_AC3
,
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.priv_data_size =
sizeof
(
AC3EncodeContext
),
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.
init
=
ac3_fixed_encode_init
,
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.encode =
ff_ac3_fixed_encode_frame
,
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.
close
=
ff_ac3_encode_close
,
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.sample_fmts = (
const
enum
AVSampleFormat
[]){
AV_SAMPLE_FMT_S16
,
AV_SAMPLE_FMT_NONE
},
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.long_name =
NULL_IF_CONFIG_SMALL
(
"ATSC A/52A (AC-3)"
),
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.priv_class = &
ac3enc_class
,
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.channel_layouts =
ff_ac3_channel_layouts
,
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};