* Common code between AC3 encoder and decoder
* Copyright (c) 2000, 2001, 2002 Fabrice Bellard.
*
- * This library is free software; you can redistribute it and/or
+ * 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 of the License, or (at your option) any later version.
+ * version 2.1 of the License, or (at your option) any later version.
*
- * This library is distributed in the hope that it will be useful,
+ * 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 this library; if not, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
+ * License along with FFmpeg; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+/**
+ * @file ac3.h
+ * Common code between AC3 encoder and decoder.
*/
+#ifndef FFMPEG_AC3_H
+#define FFMPEG_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_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;
-extern const UINT16 ac3_freqs[3];
-extern const UINT16 ac3_bitratetab[19];
-extern const INT16 ac3_window[256];
-extern const UINT8 sdecaytab[4];
-extern const UINT8 fdecaytab[4];
-extern const UINT16 sgaintab[4];
-extern const UINT16 dbkneetab[4];
-extern const UINT16 floortab[8];
-extern const UINT16 fgaintab[8];
+/**
+ * @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;
+ /** @} */
+
+ /** @defgroup derived Derived values
+ * @{
+ */
+ uint8_t sr_shift;
+ uint16_t sample_rate;
+ uint32_t bit_rate;
+ uint8_t channels;
+ uint16_t frame_size;
+ int center_mix_level; ///< Center mix level index
+ int surround_mix_level; ///< Surround mix level index
+ uint16_t channel_map;
+ /** @} */
+} 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);
-void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, UINT8 *bap,
- INT8 *exp, int start, int end,
- int snroffset, int fgain, int is_lfe,
- int deltbae,int deltnseg,
- UINT8 *deltoffst, UINT8 *deltlen, UINT8 *deltba);
+
+/**
+ * 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
+ */
+void 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[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, uint8_t *bap);
+
+void ac3_parametric_bit_allocation(AC3BitAllocParameters *s, uint8_t *bap,
+ int8_t *exp, int start, int end,
+ 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 /* FFMPEG_AC3_H */
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