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https://github.com/librempeg/librempeg
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split ac3_parametric_bit_allocation into 3 separate functions
Originally committed as revision 8442 to svn://svn.ffmpeg.org/ffmpeg/trunk
This commit is contained in:
Justin Ruggles
parent
f8b9830b6c
commit
575bf46f16
@ -50,20 +50,10 @@ static inline int calc_lowcomp(int a, int b0, int b1, int bin)
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}
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}
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/* AC3 bit allocation. The algorithm is the one described in the AC3
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spec. */
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void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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int8_t *exp, int start, int end,
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int snroffset, int fgain, int is_lfe,
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int deltbae,int deltnseg,
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uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba)
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void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
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int16_t *bndpsd)
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{
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int bin,i,j,k,end1,v,bndstrt,bndend,lowcomp,begin;
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int fastleak,slowleak,address,tmp;
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int16_t psd[256]; /* scaled exponents */
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int16_t bndpsd[50]; /* interpolated exponents */
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int16_t excite[50]; /* excitation */
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int16_t mask[50]; /* masking value */
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int bin, i, j, k, end1, v;
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/* exponent mapping to PSD */
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for(bin=start;bin<end;bin++) {
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@ -86,6 +76,18 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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bndpsd[k]=v;
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k++;
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} while (end > bndtab[k]);
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}
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void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd,
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int start, int end, int fgain, int is_lfe,
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int deltbae, int deltnseg, uint8_t *deltoffst,
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uint8_t *deltlen, uint8_t *deltba,
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int16_t *mask)
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{
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int16_t excite[50]; /* excitation */
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int bin, k;
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int bndstrt, bndend, begin, end1, tmp;
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int lowcomp, fastleak, slowleak;
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/* excitation function */
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bndstrt = masktab[start];
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@ -166,13 +168,17 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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}
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}
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}
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}
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/* compute bit allocation */
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void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
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int snroffset, int floor, uint8_t *bap)
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{
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int i, j, k, end1, v, address;
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i = start;
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j = masktab[start];
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do {
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v = (FFMAX(mask[j] - snroffset - s->floor, 0) & 0x1FE0) + s->floor;
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v = (FFMAX(mask[j] - snroffset - floor, 0) & 0x1FE0) + floor;
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end1 = FFMIN(bndtab[j] + bndsz[j], end);
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for (k = i; k < end1; k++) {
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address = av_clip((psd[i] - v) >> 5, 0, 63);
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@ -182,6 +188,28 @@ void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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} while (end > bndtab[j++]);
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}
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/* AC3 bit allocation. The algorithm is the one described in the AC3
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spec. */
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void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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int8_t *exp, int start, int end,
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int snroffset, int fgain, int is_lfe,
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int deltbae,int deltnseg,
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uint8_t *deltoffst, uint8_t *deltlen,
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uint8_t *deltba)
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{
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int16_t psd[256]; /* scaled exponents */
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int16_t bndpsd[50]; /* interpolated exponents */
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int16_t mask[50]; /* masking value */
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ff_ac3_bit_alloc_calc_psd(exp, start, end, psd, bndpsd);
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ff_ac3_bit_alloc_calc_mask(s, bndpsd, start, end, fgain, is_lfe,
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deltbae, deltnseg, deltoffst, deltlen, deltba,
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mask);
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ff_ac3_bit_alloc_calc_bap(mask, psd, start, end, snroffset, s->floor, bap);
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}
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/**
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* Initializes some tables.
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* note: This function must remain thread safe because it is called by the
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@ -102,6 +102,68 @@ extern const int16_t ff_floortab[8];
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extern const uint16_t ff_fgaintab[8];
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void ac3_common_init(void);
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/**
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* Calculates the log power-spectral density of the input signal.
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* This gives a rough estimate of signal power in the frequency domain by using
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* the spectral envelope (exponents). The psd is also separately grouped
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* into critical bands for use in the calculating the masking curve.
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* 128 units in psd = -6 dB. The dbknee parameter in AC3BitAllocParameters
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* determines the reference level.
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*
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* @param[in] exp frequency coefficient exponents
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* @param[in] start starting bin location
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* @param[in] end ending bin location
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* @param[out] psd signal power for each frequency bin
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* @param[out] bndpsd signal power for each critical band
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*/
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void ff_ac3_bit_alloc_calc_psd(int8_t *exp, int start, int end, int16_t *psd,
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int16_t *bndpsd);
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/**
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* Calculates the masking curve.
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* First, the excitation is calculated using parameters in \p s and the signal
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* power in each critical band. The excitation is compared with a predefined
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* hearing threshold table to produce the masking curve. If delta bit
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* allocation information is provided, it is used for adjusting the masking
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* curve, usually to give a closer match to a better psychoacoustic model.
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*
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* @param[in] s adjustable bit allocation parameters
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* @param[in] bndpsd signal power for each critical band
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* @param[in] start starting bin location
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* @param[in] end ending bin location
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* @param[in] fgain fast gain (estimated signal-to-mask ratio)
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* @param[in] is_lfe whether or not the channel being processed is the LFE
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* @param[in] deltbae delta bit allocation exists (none, reuse, or new)
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* @param[in] deltnseg number of delta segments
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* @param[in] deltoffst location offsets for each segment
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* @param[in] deltlen length of each segment
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* @param[in] deltba delta bit allocation for each segment
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* @param[out] mask calculated masking curve
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*/
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void ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *bndpsd,
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int start, int end, int fgain, int is_lfe,
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int deltbae, int deltnseg, uint8_t *deltoffst,
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uint8_t *deltlen, uint8_t *deltba,
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int16_t *mask);
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/**
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* Calculates bit allocation pointers.
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* The SNR is the difference between the masking curve and the signal. AC-3
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* uses this value for each frequency bin to allocate bits. The \p snroffset
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* parameter is a global adjustment to the SNR for all bins.
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*
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* @param[in] mask masking curve
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* @param[in] psd signal power for each frequency bin
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* @param[in] start starting bin location
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* @param[in] end ending bin location
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* @param[in] snroffset SNR adjustment
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* @param[in] floor noise floor
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* @param[out] bap bit allocation pointers
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*/
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void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
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int snroffset, int floor, uint8_t *bap);
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void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
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int8_t *exp, int start, int end,
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int snroffset, int fgain, int is_lfe,
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