182 lines
6.1 KiB
C
182 lines
6.1 KiB
C
/*
|
|
* Common code between the AC-3 encoder and decoder
|
|
* Copyright (c) 2000, 2001, 2002 Fabrice Bellard
|
|
*
|
|
* This file is part of FFmpeg.
|
|
*
|
|
* FFmpeg is free software; you can redistribute it and/or
|
|
* modify it under the terms of the GNU Lesser General Public
|
|
* License as published by the Free Software Foundation; either
|
|
* version 2.1 of the License, or (at your option) any later version.
|
|
*
|
|
* FFmpeg is distributed in the hope that it will be useful,
|
|
* but WITHOUT ANY WARRANTY; without even the implied warranty of
|
|
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
|
|
* Lesser General Public License for more details.
|
|
*
|
|
* You should have received a copy of the GNU Lesser General Public
|
|
* License along with FFmpeg; if not, write to the Free Software
|
|
* Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
|
|
*/
|
|
|
|
/**
|
|
* @file
|
|
* Common code between the AC-3 encoder and decoder.
|
|
*/
|
|
|
|
#ifndef AVCODEC_AC3_H
|
|
#define AVCODEC_AC3_H
|
|
|
|
#define AC3_MAX_CODED_FRAME_SIZE 3840 /* in bytes */
|
|
#define AC3_MAX_CHANNELS 7 /**< maximum number of channels, including coupling channel */
|
|
#define CPL_CH 0 /**< coupling channel index */
|
|
|
|
#define AC3_MAX_COEFS 256
|
|
#define AC3_BLOCK_SIZE 256
|
|
#define AC3_MAX_BLOCKS 6
|
|
#define AC3_FRAME_SIZE (AC3_MAX_BLOCKS * 256)
|
|
#define AC3_WINDOW_SIZE (AC3_BLOCK_SIZE * 2)
|
|
#define AC3_CRITICAL_BANDS 50
|
|
#define AC3_MAX_CPL_BANDS 18
|
|
|
|
#include "libavutil/opt.h"
|
|
#include "avcodec.h"
|
|
#include "ac3tab.h"
|
|
|
|
/* exponent encoding strategy */
|
|
#define EXP_REUSE 0
|
|
#define EXP_NEW 1
|
|
|
|
#define EXP_D15 1
|
|
#define EXP_D25 2
|
|
#define EXP_D45 3
|
|
|
|
/* pre-defined gain values */
|
|
#define LEVEL_PLUS_3DB 1.4142135623730950
|
|
#define LEVEL_PLUS_1POINT5DB 1.1892071150027209
|
|
#define LEVEL_MINUS_1POINT5DB 0.8408964152537145
|
|
#define LEVEL_MINUS_3DB 0.7071067811865476
|
|
#define LEVEL_MINUS_4POINT5DB 0.5946035575013605
|
|
#define LEVEL_MINUS_6DB 0.5000000000000000
|
|
#define LEVEL_MINUS_9DB 0.3535533905932738
|
|
#define LEVEL_ZERO 0.0000000000000000
|
|
#define LEVEL_ONE 1.0000000000000000
|
|
|
|
/** 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 sr_code;
|
|
int sr_shift;
|
|
int slow_gain, slow_decay, fast_decay, db_per_bit, floor;
|
|
int cpl_fast_leak, cpl_slow_leak;
|
|
} AC3BitAllocParameters;
|
|
|
|
/**
|
|
* @struct AC3HeaderInfo
|
|
* Coded AC-3 header values up to the lfeon element, plus derived values.
|
|
*/
|
|
typedef struct AC3HeaderInfo {
|
|
/** @name Coded elements
|
|
* @{
|
|
*/
|
|
uint16_t sync_word;
|
|
uint16_t crc1;
|
|
uint8_t sr_code;
|
|
uint8_t bitstream_id;
|
|
uint8_t bitstream_mode;
|
|
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
|
|
/** @} */
|
|
|
|
/** @name Derived values
|
|
* @{
|
|
*/
|
|
uint8_t sr_shift;
|
|
uint16_t sample_rate;
|
|
uint32_t bit_rate;
|
|
uint8_t channels;
|
|
uint16_t frame_size;
|
|
uint64_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 ff_ac3_common_init(void);
|
|
|
|
/**
|
|
* Calculate 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);
|
|
|
|
/**
|
|
* Calculate the masking curve.
|
|
* First, the excitation is calculated using parameters in 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);
|
|
|
|
#endif /* AVCODEC_AC3_H */
|