ac3enc_fixed.c
Go to the documentation of this file.
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 
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"
36 static const AVClass ac3enc_class = { "Fixed-Point AC-3 Encoder", av_default_item_name,
38 
39 #include "ac3enc_template.c"
40 
41 
48 {
49  ff_mdct_end(&s->mdct);
50 }
51 
52 
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  */
70 static 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  */
82 {
84  v = 14 - av_log2(v);
85  if (v > 0)
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  */
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++) {
103  block->coeff_shift[ch]);
104  }
105  }
106 }
107 
108 
109 /*
110  * Clip MDCT coefficients to allowable range.
111  */
112 static 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  */
121 static 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 
135 {
136  AC3EncodeContext *s = avctx->priv_data;
137  s->fixed_point = 1;
138  return ff_ac3_encode_init(avctx);
139 }
140 
141 
143  .name = "ac3_fixed",
144  .type = AVMEDIA_TYPE_AUDIO,
145  .id = CODEC_ID_AC3,
146  .priv_data_size = sizeof(AC3EncodeContext),
148  .encode = ff_ac3_fixed_encode_frame,
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 };
void(* ac3_rshift_int32)(int32_t *src, unsigned int len, unsigned int shift)
Right-shift each value in an array of int32_t by a specified amount.
Definition: ac3dsp.h:76
struct AC3EncodeContext AC3EncodeContext
AC-3 encoder private context.
#define AC3_MAX_COEFS
Definition: ac3.h:34
static av_cold int ac3_fixed_encode_init(AVCodecContext *avctx)
Definition: ac3enc_fixed.c:134
#define AC3_WINDOW_SIZE
Definition: ac3.h:38
#define COEF_MIN
Definition: ac3enc.h:62
void(* apply_window_int16)(int16_t *output, const int16_t *input, const int16_t *window, unsigned int len)
Apply symmetric window in 16-bit fixed-point.
Definition: dsputil.h:564
signed 16 bits
Definition: samplefmt.h:30
#define blk(i)
Definition: sha.c:163
AVCodec.
Definition: avcodec.h:3189
#define v(n)
Definition: regs.h:34
static av_const unsigned int ff_sqrt(unsigned int a)
Definition: intmath.h:64
#define av_cold
Definition: attributes.h:71
av_cold int AC3_NAME() mdct_init(AC3EncodeContext *s)
Initialize MDCT tables.
Definition: ac3enc_fixed.c:59
int(* ac3_max_msb_abs_int16)(const int16_t *src, int len)
Calculate the maximum MSB of the absolute value of each element in an array of int16_t.
Definition: ac3dsp.h:54
av_cold int ff_ac3_encode_close(AVCodecContext *avctx)
Finalize encoding and free any memory allocated by the encoder.
Definition: ac3enc.c:2020
static const AVOption ac3fixed_options[]
const int16_t ff_ac3_window[AC3_WINDOW_SIZE/2]
Definition: ac3tab.c:151
AC3DSPContext ac3dsp
AC-3 optimized functions.
Definition: ac3enc.h:161
av_cold void AC3_NAME() mdct_end(AC3EncodeContext *s)
Finalize MDCT and free allocated memory.
Definition: ac3enc_fixed.c:47
static int init(AVCodecParserContext *s)
Definition: h264_parser.c:336
static DSPContext dsp
Definition: atrac3.c:135
int64_t CoefSumType
Definition: ac3enc.h:67
CoefType ** mdct_coef
MDCT coefficients.
Definition: ac3enc.h:127
const uint64_t ff_ac3_channel_layouts[19]
List of supported channel layouts.
Definition: ac3enc.c:80
int channels
total number of channels (nchans)
Definition: ac3enc.h:185
#define NULL_IF_CONFIG_SMALL(x)
Return NULL if CONFIG_SMALL is true, otherwise the argument without modification. ...
Definition: internal.h:191
#define AC3_NAME(x)
Definition: ac3enc.h:60
const char * name
Name of the codec implementation.
Definition: avcodec.h:3196
int fixed_point
indicates if fixed-point encoder is being used
Definition: ac3enc.h:167
#define ff_mdct_init
Definition: fft.h:146
Data for a single audio block.
Definition: ac3enc.h:126
static DCTELEM block[64]
Definition: dct-test.c:189
#define FFMIN(a, b)
Definition: common.h:55
LIBAVUTIL_VERSION_INT
Definition: eval.c:50
static void scale_coefficients(AC3EncodeContext *s)
Definition: ac3enc_fixed.c:95
static CoefType calc_cpl_coord(CoefSumType energy_ch, CoefSumType energy_cpl)
Definition: ac3enc_fixed.c:121
av_default_item_name
Definition: dnxhdenc.c:43
main external API structure.
Definition: avcodec.h:1329
static void close(AVCodecParserContext *s)
Definition: h264_parser.c:327
Describe the class of an AVClass context structure.
Definition: log.h:33
AC-3 encoder private context.
Definition: ac3enc.h:155
AC3Block blocks[AC3_MAX_BLOCKS]
per-block info
Definition: ac3enc.h:165
SampleType * windowed_samples
Definition: ac3enc.h:227
int num_blocks
number of blocks per frame
Definition: ac3enc.h:176
uint8_t coeff_shift[AC3_MAX_CHANNELS]
fixed-point coefficient shift values
Definition: ac3enc.h:137
static void clip_coefficients(DSPContext *dsp, int32_t *coef, unsigned int len)
Definition: ac3enc_fixed.c:112
void(* vector_clip_int32)(int32_t *dst, const int32_t *src, int32_t min, int32_t max, unsigned int len)
Clip each element in an array of int32_t to a given minimum and maximum value.
Definition: dsputil.h:580
#define COEF_MAX
Definition: ac3enc.h:63
int ff_ac3_fixed_encode_frame(AVCodecContext *avctx, unsigned char *frame, int buf_size, void *data)
AC-3 encoder float/fixed template.
AVCodec ff_ac3_fixed_encoder
Definition: ac3enc_fixed.c:142
#define ff_mdct_end
Definition: fft.h:147
static const AVClass ac3enc_class
Definition: ac3enc_fixed.c:36
AVSampleFormat
all in native-endian format
Definition: samplefmt.h:27
void(* ac3_lshift_int16)(int16_t *src, unsigned int len, unsigned int shift)
Left-shift each value in an array of int16_t by a specified amount.
Definition: ac3dsp.h:65
AVCodecContext * avctx
parent AVCodecContext
Definition: ac3enc.h:158
void * priv_data
Definition: avcodec.h:1531
int len
static int normalize_samples(AC3EncodeContext *s)
Definition: ac3enc_fixed.c:81
AC-3 encoder & E-AC-3 encoder common header.
int32_t CoefType
Definition: ac3enc.h:66
E-AC-3 encoder.
static void apply_window(DSPContext *dsp, int16_t *output, const int16_t *input, const int16_t *window, unsigned int len)
Definition: ac3enc_fixed.c:70
DSPContext.
Definition: dsputil.h:226
av_cold int ff_ac3_encode_init(AVCodecContext *avctx)
Definition: ac3enc.c:2410