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Functions  
static int  calc_lowcomp1 (int a, int b0, int b1, int c) 
static int  calc_lowcomp (int a, int b0, int b1, int bin) 
void  ff_ac3_bit_alloc_calc_psd (int8_t *exp, int start, int end, int16_t *psd, int16_t *band_psd) 
Calculate the log powerspectral density of the input signal. More...  
int  ff_ac3_bit_alloc_calc_mask (AC3BitAllocParameters *s, int16_t *band_psd, int start, int end, int fast_gain, int is_lfe, int dba_mode, int dba_nsegs, uint8_t *dba_offsets, uint8_t *dba_lengths, uint8_t *dba_values, int16_t *mask) 
Calculate the masking curve. More...  
Variables  
const uint8_t  ff_ac3_band_start_tab [AC3_CRITICAL_BANDS+1] 
Starting frequency coefficient bin for each critical band. More...  
const uint8_t  ff_ac3_bin_to_band_tab [253] 
Map each frequency coefficient bin to the critical band that contains it. More...  
static const uint8_t  ac3_log_add_tab [260] 
static const uint16_t  ac3_hearing_threshold_tab [AC3_CRITICAL_BANDS][3] 
Common code between the AC3 encoder and decoder.
Definition in file ac3.c.
Definition at line 154 of file ac3.c.
Referenced by calc_lowcomp(), and ff_ac3_bit_alloc_calc_mask().
Definition at line 164 of file ac3.c.
Referenced by ff_ac3_bit_alloc_calc_mask().
void ff_ac3_bit_alloc_calc_psd  (  int8_t *  exp, 
int  start,  
int  end,  
int16_t *  psd,  
int16_t *  band_psd  
) 
Calculate the log powerspectral density of the input signal.
This gives a rough estimate of signal power in the frequency domain by using the spectral envelope (exponents). The psd is also separately grouped into critical bands for use in the calculating the masking curve. 128 units in psd = 6 dB. The dbknee parameter in AC3BitAllocParameters determines the reference level.
[in]  exp  frequency coefficient exponents 
[in]  start  starting bin location 
[in]  end  ending bin location 
[out]  psd  signal power for each frequency bin 
[out]  band_psd  signal power for each critical band 
Definition at line 175 of file ac3.c.
Referenced by bit_alloc_masking(), and decode_audio_block().
int ff_ac3_bit_alloc_calc_mask  (  AC3BitAllocParameters *  s, 
int16_t *  band_psd,  
int  start,  
int  end,  
int  fast_gain,  
int  is_lfe,  
int  dba_mode,  
int  dba_nsegs,  
uint8_t *  dba_offsets,  
uint8_t *  dba_lengths,  
uint8_t *  dba_values,  
int16_t *  mask  
) 
Calculate the masking curve.
First, the excitation is calculated using parameters in s and the signal power in each critical band. The excitation is compared with a predefined hearing threshold table to produce the masking curve. If delta bit allocation information is provided, it is used for adjusting the masking curve, usually to give a closer match to a better psychoacoustic model.
[in]  s  adjustable bit allocation parameters 
[in]  band_psd  signal power for each critical band 
[in]  start  starting bin location 
[in]  end  ending bin location 
[in]  fast_gain  fast gain (estimated signaltomask ratio) 
[in]  is_lfe  whether or not the channel being processed is the LFE 
[in]  dba_mode  delta bit allocation mode (none, reuse, or new) 
[in]  dba_nsegs  number of delta segments 
[in]  dba_offsets  location offsets for each segment 
[in]  dba_lengths  length of each segment 
[in]  dba_values  delta bit allocation for each segment 
[out]  mask  calculated masking curve 
Definition at line 201 of file ac3.c.
Referenced by bit_alloc_masking(), and decode_audio_block().
const uint8_t ff_ac3_band_start_tab[AC3_CRITICAL_BANDS+1] 
Starting frequency coefficient bin for each critical band.
Definition at line 36 of file ac3.c.
Referenced by ac3_bit_alloc_calc_bap_c(), and ff_ac3_bit_alloc_calc_psd().
const uint8_t ff_ac3_bin_to_band_tab[253] 
Map each frequency coefficient bin to the critical band that contains it.
Definition at line 47 of file ac3.c.
Referenced by ac3_bit_alloc_calc_bap_c(), ff_ac3_bit_alloc_calc_mask(), and ff_ac3_bit_alloc_calc_psd().

static 
Definition at line 72 of file ac3.c.
Referenced by ff_ac3_bit_alloc_calc_psd().

static 
Definition at line 101 of file ac3.c.
Referenced by ff_ac3_bit_alloc_calc_mask().