* Common code between AC3 encoder and decoder.
*/
+#ifndef AC3_H
+#define AC3_H
+
+#include "ac3tab.h"
+
#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
#define AC3_MAX_CHANNELS 6 /* including LFE channel */
#define EXP_D25 2
#define EXP_D45 3
+/** Delta bit allocation strategy */
+typedef enum {
+ DBA_REUSE = 0,
+ DBA_NEW,
+ DBA_NONE,
+ DBA_RESERVED
+} AC3DeltaStrategy;
+
+/** Channel mode (audio coding mode) */
+typedef enum {
+ AC3_ACMOD_DUALMONO = 0,
+ AC3_ACMOD_MONO,
+ AC3_ACMOD_STEREO,
+ AC3_ACMOD_3F,
+ AC3_ACMOD_2F1R,
+ AC3_ACMOD_3F1R,
+ AC3_ACMOD_2F2R,
+ AC3_ACMOD_3F2R
+} AC3ChannelMode;
+
typedef struct AC3BitAllocParameters {
int fscod; /* frequency */
int halfratecod;
int cplfleak, cplsleak;
} AC3BitAllocParameters;
-#if 0
-extern const uint16_t ac3_freqs[3];
-extern const uint16_t ac3_bitratetab[19];
-extern const int16_t ac3_window[256];
-extern const uint8_t sdecaytab[4];
-extern const uint8_t fdecaytab[4];
-extern const uint16_t sgaintab[4];
-extern const uint16_t dbkneetab[4];
-extern const uint16_t floortab[8];
-extern const uint16_t fgaintab[8];
-#endif
+/**
+ * @struct AC3HeaderInfo
+ * Coded AC-3 header values up to the lfeon element, plus derived values.
+ */
+typedef struct {
+ /** @defgroup coded Coded elements
+ * @{
+ */
+ uint16_t sync_word;
+ uint16_t crc1;
+ uint8_t fscod;
+ uint8_t frmsizecod;
+ uint8_t bsid;
+ uint8_t bsmod;
+ uint8_t acmod;
+ uint8_t cmixlev;
+ uint8_t surmixlev;
+ uint8_t dsurmod;
+ uint8_t lfeon;
+ /** @} */
+
+ /** @defgroup derived Derived values
+ * @{
+ */
+ uint8_t halfratecod;
+ uint16_t sample_rate;
+ uint32_t bit_rate;
+ uint8_t channels;
+ uint16_t frame_size;
+ /** @} */
+} AC3HeaderInfo;
+
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,
int deltbae,int deltnseg,
uint8_t *deltoffst, uint8_t *deltlen, uint8_t *deltba);
+
+#endif /* AC3_H */