Commit 575bf46f authored by Justin Ruggles's avatar Justin Ruggles
Browse files

split ac3_parametric_bit_allocation into 3 separate functions

Originally committed as revision 8442 to svn://svn.ffmpeg.org/ffmpeg/trunk
parent f8b9830b
......@@ -50,20 +50,10 @@ static inline int calc_lowcomp(int a, int b0, int b1, int bin)
}
}
/* AC3 bit allocation. The algorithm is the one described in the AC3
spec. */
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
int8_t *exp, int start, int end,
int snroffset, int fgain, int is_lfe,
int deltbae,int deltnseg,
uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
int16_t *bndpsd)
{
int bin,i,j,k,end1,v,bndstrt,bndend,lowcomp,begin;
int fastleak,slowleak,address,tmp;
int16_t psd[256]; /* scaled exponents */
int16_t bndpsd[50]; /* interpolated exponents */
int16_t excite[50]; /* excitation */
int16_t mask[50]; /* masking value */
int bin, i, j, k, end1, v;
/* exponent mapping to PSD */
for(bin=start;bin<end;bin++) {
......@@ -86,6 +76,18 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
bndpsd[k]=v;
k++;
} while (end > bndtab[k]);
}
void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd,
int start, int end, int fgain, int is_lfe,
int deltbae, int deltnseg, uint8_t *deltoffst,
uint8_t *deltlen, uint8_t *deltba,
int16_t *mask)
{
int16_t excite[50]; /* excitation */
int bin, k;
int bndstrt, bndend, begin, end1, tmp;
int lowcomp, fastleak, slowleak;
/* excitation function */
bndstrt = masktab[start];
......@@ -166,13 +168,17 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
}
}
}
}
/* compute bit allocation */
void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
int snroffset, int floor, uint8_t *bap)
{
int i, j, k, end1, v, address;
i = start;
j = masktab[start];
do {
v = (FFMAX(mask[j] - snroffset - s->floor, 0) & 0x1FE0) + s->floor;
v = (FFMAX(mask[j] - snroffset - floor, 0) & 0x1FE0) + floor;
end1 = FFMIN(bndtab[j] + bndsz[j], end);
for (k = i; k < end1; k++) {
address = av_clip((psd[i] - v) >> 5, 0, 63);
......@@ -182,6 +188,28 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
} while (end > bndtab[j++]);
}
/* AC3 bit allocation. The algorithm is the one described in the AC3
spec. */
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
int8_t *exp, int start, int end,
int snroffset, int fgain, int is_lfe,
int deltbae,int deltnseg,
uint8_t *deltoffst, uint8_t *deltlen,
uint8_t *deltba)
{
int16_t psd[256]; /* scaled exponents */
int16_t bndpsd[50]; /* interpolated exponents */
int16_t mask[50]; /* masking value */
ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, bndpsd);
ff_ac3_bit_alloc_calc_mask(s, bndpsd, start, end, fgain, is_lfe,
deltbae, deltnseg, deltoffst, deltlen, deltba,
mask);
ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snroffset, s->floor, bap);
}
/**
* Initializes some tables.
* note: This function must remain thread safe because it is called by the
......
......@@ -102,6 +102,68 @@ extern const int16_t ff_floortab[8];
extern const uint16_t ff_fgaintab[8];
void ac3_common_init(void);
/**
* Calculates the log power-spectral 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.
*
* @param[in] exp frequency coefficient exponents
* @param[in] start starting bin location
* @param[in] end ending bin location
* @param[out] psd signal power for each frequency bin
* @param[out] bndpsd signal power for each critical band
*/
void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
int16_t *bndpsd);
/**
* Calculates the masking curve.
* First, the excitation is calculated using parameters in \p 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.
*
* @param[in] s adjustable bit allocation parameters
* @param[in] bndpsd signal power for each critical band
* @param[in] start starting bin location
* @param[in] end ending bin location
* @param[in] fgain fast gain (estimated signal-to-mask ratio)
* @param[in] is_lfe whether or not the channel being processed is the LFE
* @param[in] deltbae delta bit allocation exists (none, reuse, or new)
* @param[in] deltnseg number of delta segments
* @param[in] deltoffst location offsets for each segment
* @param[in] deltlen length of each segment
* @param[in] deltba delta bit allocation for each segment
* @param[out] mask calculated masking curve
*/
void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd,
int start, int end, int fgain, int is_lfe,
int deltbae, int deltnseg, uint8_t *deltoffst,
uint8_t *deltlen, uint8_t *deltba,
int16_t *mask);
/**
* Calculates bit allocation pointers.
* The SNR is the difference between the masking curve and the signal. AC-3
* uses this value for each frequency bin to allocate bits. The \p snroffset
* parameter is a global adjustment to the SNR for all bins.
*
* @param[in] mask masking curve
* @param[in] psd signal power for each frequency bin
* @param[in] start starting bin location
* @param[in] end ending bin location
* @param[in] snroffset SNR adjustment
* @param[in] floor noise floor
* @param[out] bap bit allocation pointers
*/
void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
int snroffset, int floor, uint8_t *bap);
void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
int8_t *exp, int start, int end,
int snroffset, int fgain, int is_lfe,
......
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