libavcodec/ac3.h

   1 /*
   2  * Common code between the AC-3 encoder and decoder
   3  * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
   4  *
   5  * This file is part of FFmpeg.
   6  *
   7  * FFmpeg is free software; you can redistribute it and/or
   8  * modify it under the terms of the GNU Lesser General Public
   9  * License as published by the Free Software Foundation; either
  10  * version 2.1 of the License, or (at your option) any later version.
  11  *
  12  * FFmpeg is distributed in the hope that it will be useful,
  13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  15  * Lesser General Public License for more details.
  16  *
  17  * You should have received a copy of the GNU Lesser General Public
  18  * License along with FFmpeg; if not, write to the Free Software
  19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
  20  */
  21
  22 /**
  23  * @file
  24  * Common code between the AC-3 encoder and decoder.
  25  */
  26
  27 #ifndef AVCODEC_AC3_H
  28 #define AVCODEC_AC3_H
  29
  30 #include <math.h>
  31 #include <stdint.h>
  32
  33 #include "ac3tab.h"
  34
  35 #ifndef USE_FIXED
  36 #define USE_FIXED 0
  37 #endif
  38
  39 #if USE_FIXED
  40
  41 #define FIXR(a)                 ((int)((a) * 0 + 0.5))
  42 #define FIXR12(a)               ((int)((a) * 4096 + 0.5))
  43 #define FIXR15(a)               ((int)((a) * 32768 + 0.5))
  44 #define ROUND15(x)              ((x) + 16384) >> 15
  45
  46 #define AC3_RENAME(x)           x ## _fixed
  47 #define AC3_NORM(norm)          (1<<24)/(norm)
  48 #define AC3_MUL(a,b)            ((((int64_t) (a)) * (b))>>12)
  49 #define AC3_RANGE(x)            ((x)|(((x)&128)<<1))
  50 #define AC3_HEAVY_RANGE(x)      ((x)<<1)
  51 #define AC3_DYNAMIC_RANGE(x)    (x)
  52 #define AC3_SPX_BLEND(x)        (x)
  53 #define AC3_DYNAMIC_RANGE1      0
  54
  55 typedef int                     INTFLOAT;
  56 typedef unsigned int            UINTFLOAT;
  57 typedef int16_t                 SHORTFLOAT;
  58
  59 #else /* USE_FIXED */
  60 #include "libavutil/libm.h"
  61
  62 #define FIXR(x)                 ((float)(x))
  63 #define FIXR12(x)               ((float)(x))
  64 #define FIXR15(x)               ((float)(x))
  65 #define ROUND15(x)              (x)
  66
  67 #define AC3_RENAME(x)           x
  68 #define AC3_NORM(norm)          (1.0f/(norm))
  69 #define AC3_MUL(a,b)            ((a) * (b))
  70 #define AC3_RANGE(x)            (dynamic_range_tab[(x)])
  71 #define AC3_HEAVY_RANGE(x)      (ff_ac3_heavy_dynamic_range_tab[(x)])
  72 #define AC3_DYNAMIC_RANGE(x)    (powf(x,  s->drc_scale))
  73 #define AC3_SPX_BLEND(x)        (x)* (1.0f/32)
  74 #define AC3_DYNAMIC_RANGE1      1.0f
  75
  76 typedef float                   INTFLOAT;
  77 typedef float                   UINTFLOAT;
  78 typedef float                   SHORTFLOAT;
  79
  80 #endif /* USE_FIXED */
  81
  82 #define AC3_LEVEL(x)            ROUND15((x) * FIXR15(M_SQRT1_2))
  83
  84 /* pre-defined gain values */
  85 #define LEVEL_PLUS_3DB          M_SQRT2
  86 #define LEVEL_PLUS_1POINT5DB    1.1892071150027209
  87 #define LEVEL_MINUS_1POINT5DB   0.8408964152537145
  88 #define LEVEL_MINUS_3DB         M_SQRT1_2
  89 #define LEVEL_MINUS_4POINT5DB   0.5946035575013605
  90 #define LEVEL_MINUS_6DB         0.5000000000000000
  91 #define LEVEL_MINUS_9DB         0.3535533905932738
  92 #define LEVEL_ZERO              0.0000000000000000
  93 #define LEVEL_ONE               1.0000000000000000
  94
  95 typedef struct AC3BitAllocParameters {
  96     int sr_code;
  97     int sr_shift;
  98     int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
  99     int cpl_fast_leak, cpl_slow_leak;
 100 } AC3BitAllocParameters;
 101
 102 /**
 103  * Calculate the log power-spectral density of the input signal.
 104  * This gives a rough estimate of signal power in the frequency domain by using
 105  * the spectral envelope (exponents).  The psd is also separately grouped
 106  * into critical bands for use in the calculating the masking curve.
 107  * 128 units in psd = -6 dB.  The dbknee parameter in AC3BitAllocParameters
 108  * determines the reference level.
 109  *
 110  * @param[in]  exp        frequency coefficient exponents
 111  * @param[in]  start      starting bin location
 112  * @param[in]  end        ending bin location
 113  * @param[out] psd        signal power for each frequency bin
 114  * @param[out] band_psd   signal power for each critical band
 115  */
 116 void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
 117                                int16_t *band_psd);
 118
 119 /**
 120  * Calculate the masking curve.
 121  * First, the excitation is calculated using parameters in s and the signal
 122  * power in each critical band.  The excitation is compared with a predefined
 123  * hearing threshold table to produce the masking curve.  If delta bit
 124  * allocation information is provided, it is used for adjusting the masking
 125  * curve, usually to give a closer match to a better psychoacoustic model.
 126  *
 127  * @param[in]  s            adjustable bit allocation parameters
 128  * @param[in]  band_psd     signal power for each critical band
 129  * @param[in]  start        starting bin location
 130  * @param[in]  end          ending bin location
 131  * @param[in]  fast_gain    fast gain (estimated signal-to-mask ratio)
 132  * @param[in]  is_lfe       whether or not the channel being processed is the LFE
 133  * @param[in]  dba_mode     delta bit allocation mode (none, reuse, or new)
 134  * @param[in]  dba_nsegs    number of delta segments
 135  * @param[in]  dba_offsets  location offsets for each segment
 136  * @param[in]  dba_lengths  length of each segment
 137  * @param[in]  dba_values   delta bit allocation for each segment
 138  * @param[out] mask         calculated masking curve
 139  * @return returns 0 for success, non-zero for error
 140  */
 141 int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
 142                                int start, int end, int fast_gain, int is_lfe,
 143                                int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
 144                                uint8_t *dba_lengths, uint8_t *dba_values,
 145                                int16_t *mask);
 146
 147 #endif /* AVCODEC_AC3_H */