split ac3_parametric_bit_allocation into 3 separate functions

Originally committed as revision 8442 to svn://svn.ffmpeg.org/ffmpeg/trunk

1 files changed, 62 insertions, 0 deletions

diff --git a/libavcodec/ac3.h b/libavcodec/ac3.h
index bd7e7b611b..ae53a80c3d 100644
--- a/libavcodec/ac3.h
+++ b/libavcodec/ac3.h
@@ -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,