[Ffmpeg-cvslog] r8442 - in trunk/libavcodec: ac3.c ac3.h
jbr
subversion
Sun Mar 18 22:43:20 CET 2007
Author: jbr
Date: Sun Mar 18 22:43:20 2007
New Revision: 8442
Modified:
trunk/libavcodec/ac3.c
trunk/libavcodec/ac3.h
Log:
split ac3_parametric_bit_allocation into 3 separate functions
Modified: trunk/libavcodec/ac3.c
==============================================================================
--- trunk/libavcodec/ac3.c (original)
+++ trunk/libavcodec/ac3.c Sun Mar 18 22:43:20 2007
@@ -50,20 +50,10 @@ static inline int calc_lowcomp(int a, in
}
}
-/* 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(AC3Bi
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(AC3Bi
}
}
}
+}
- /* 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(AC3Bi
} 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
Modified: trunk/libavcodec/ac3.h
==============================================================================
--- trunk/libavcodec/ac3.h (original)
+++ trunk/libavcodec/ac3.h Sun Mar 18 22:43:20 2007
@@ -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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