/*
- * Common code between AC3 encoder and decoder
- * Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
+ * Common code between the AC-3 encoder and decoder
+ * Copyright (c) 2000, 2001, 2002 Fabrice Bellard
*
* This file is part of FFmpeg.
*
*/
/**
- * @file ac3.h
- * Common code between AC3 encoder and decoder.
+ * @file libavcodec/ac3.h
+ * Common code between the AC-3 encoder and decoder.
*/
+#ifndef AVCODEC_AC3_H
+#define AVCODEC_AC3_H
+
+#include "ac3tab.h"
+
#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
#define AC3_MAX_CHANNELS 6 /* including LFE channel */
-#define NB_BLOCKS 6 /* number of PCM blocks inside an AC3 frame */
+#define NB_BLOCKS 6 /* number of PCM blocks inside an AC-3 frame */
#define AC3_FRAME_SIZE (NB_BLOCKS * 256)
/* exponent encoding strategy */
#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_CHMODE_DUALMONO = 0,
+ AC3_CHMODE_MONO,
+ AC3_CHMODE_STEREO,
+ AC3_CHMODE_3F,
+ AC3_CHMODE_2F1R,
+ AC3_CHMODE_3F1R,
+ AC3_CHMODE_2F2R,
+ AC3_CHMODE_3F2R
+} AC3ChannelMode;
+
typedef struct AC3BitAllocParameters {
- int fscod; /* frequency */
- int halfratecod;
- int sgain, sdecay, fdecay, dbknee, floor;
- int cplfleak, cplsleak;
+ int sr_code;
+ int sr_shift;
+ int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
+ int cpl_fast_leak, cpl_slow_leak;
} 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 sr_code;
+ uint8_t bitstream_id;
+ uint8_t channel_mode;
+ uint8_t lfe_on;
+ uint8_t frame_type;
+ int substreamid; ///< substream identification
+ int center_mix_level; ///< Center mix level index
+ int surround_mix_level; ///< Surround mix level index
+ uint16_t channel_map;
+ int num_blocks; ///< number of audio blocks
+ /** @} */
+
+ /** @defgroup derived Derived values
+ * @{
+ */
+ uint8_t sr_shift;
+ uint16_t sample_rate;
+ uint32_t bit_rate;
+ uint8_t channels;
+ uint16_t frame_size;
+ int64_t channel_layout;
+ /** @} */
+} AC3HeaderInfo;
+
+typedef enum {
+ EAC3_FRAME_TYPE_INDEPENDENT = 0,
+ EAC3_FRAME_TYPE_DEPENDENT,
+ EAC3_FRAME_TYPE_AC3_CONVERT,
+ EAC3_FRAME_TYPE_RESERVED
+} EAC3FrameType;
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] band_psd 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 *band_psd);
+
+/**
+ * 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] band_psd signal power for each critical band
+ * @param[in] start starting bin location
+ * @param[in] end ending bin location
+ * @param[in] fast_gain fast gain (estimated signal-to-mask ratio)
+ * @param[in] is_lfe whether or not the channel being processed is the LFE
+ * @param[in] dba_mode delta bit allocation mode (none, reuse, or new)
+ * @param[in] dba_nsegs number of delta segments
+ * @param[in] dba_offsets location offsets for each segment
+ * @param[in] dba_lengths length of each segment
+ * @param[in] dba_values delta bit allocation for each segment
+ * @param[out] mask calculated masking curve
+ * @return returns 0 for success, non-zero for error
+ */
+int ff_ac3_bit_alloc_calc_mask(AC3BitAllocParameters *s, int16_t *band_psd,
+ int start, int end, int fast_gain, int is_lfe,
+ int dba_mode, int dba_nsegs, uint8_t *dba_offsets,
+ uint8_t *dba_lengths, uint8_t *dba_values,
+ 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] snr_offset SNR adjustment
+ * @param[in] floor noise floor
+ * @param[in] bap_tab look-up table for bit allocation pointers
+ * @param[out] bap bit allocation pointers
+ */
+void ff_ac3_bit_alloc_calc_bap(int16_t *mask, int16_t *psd, int start, int end,
+ int snr_offset, int floor,
+ const uint8_t *bap_tab, 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);
+ int snr_offset, int fast_gain, int is_lfe,
+ int dba_mode, int dba_nsegs,
+ uint8_t *dba_offsets, uint8_t *dba_lengths,
+ uint8_t *dba_values);
+
+#endif /* AVCODEC_AC3_H */
projects / frescor / ffmpeg.git / blobdiff