2 * audio encoder psychoacoustic model
3 * Copyright (C) 2008 Konstantin Shishkov
5 * This file is part of FFmpeg.
7 * FFmpeg is free software; you can redistribute it and/or
8 * modify it under the terms of the GNU Lesser General Public
9 * License as published by the Free Software Foundation; either
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15 * Lesser General Public License for more details.
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19 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
22 #ifndef AVCODEC_PSYMODEL_H
23 #define AVCODEC_PSYMODEL_H
27 /** maximum possible number of bands */
28 #define PSY_MAX_BANDS 128
29 /** maximum number of channels */
30 #define PSY_MAX_CHANS 20
32 #define AAC_CUTOFF(s) ((s)->bit_rate ? FFMIN3(4000 + (s)->bit_rate/8, 12000 + (s)->bit_rate/32, (s)->sample_rate / 2) : ((s)->sample_rate / 2))
35 * single band psychoacoustic information
37 typedef struct FFPsyBand
{
42 float perceptual_weight
;
46 * single channel psychoacoustic information
48 typedef struct FFPsyChannel
{
49 FFPsyBand psy_bands
[PSY_MAX_BANDS
]; ///< channel bands information
50 float entropy
; ///< total PE for this channel
54 * psychoacoustic information for an arbitrary group of channels
56 typedef struct FFPsyChannelGroup
{
57 FFPsyChannel
*ch
[PSY_MAX_CHANS
]; ///< pointers to the individual channels in the group
58 uint8_t num_ch
; ///< number of channels in this group
59 uint8_t coupling
[PSY_MAX_BANDS
]; ///< allow coupling for this band in the group
63 * windowing related information
65 typedef struct FFPsyWindowInfo
{
66 int window_type
[3]; ///< window type (short/long/transitional, etc.) - current, previous and next
67 int window_shape
; ///< window shape (sine/KBD/whatever)
68 int num_windows
; ///< number of windows in a frame
69 int grouping
[8]; ///< window grouping (for e.g. AAC)
70 int *window_sizes
; ///< sequence of window sizes inside one frame (for eg. WMA)
74 * context used by psychoacoustic model
76 typedef struct FFPsyContext
{
77 AVCodecContext
*avctx
; ///< encoder context
78 const struct FFPsyModel
*model
; ///< encoder-specific model functions
80 FFPsyChannel
*ch
; ///< single channel information
81 FFPsyChannelGroup
*group
; ///< channel group information
82 int num_groups
; ///< number of channel groups
84 uint8_t **bands
; ///< scalefactor band sizes for possible frame sizes
85 int *num_bands
; ///< number of scalefactor bands for possible frame sizes
86 int num_lens
; ///< number of scalefactor band sets
89 int size
; ///< size of the bitresevoir in bits
90 int bits
; ///< number of bits used in the bitresevoir
93 void* model_priv_data
; ///< psychoacoustic model implementation private data
97 * codec-specific psychoacoustic model implementation
99 typedef struct FFPsyModel
{
101 int (*init
) (FFPsyContext
*apc
);
104 * Suggest window sequence for channel.
106 * @param ctx model context
107 * @param audio samples for the current frame
108 * @param la lookahead samples (NULL when unavailable)
109 * @param channel number of channel element to analyze
110 * @param prev_type previous window type
112 * @return suggested window information in a structure
114 FFPsyWindowInfo (*window
)(FFPsyContext
*ctx
, const float *audio
, const float *la
, int channel
, int prev_type
);
117 * Perform psychoacoustic analysis and set band info (threshold, energy) for a group of channels.
119 * @param ctx model context
120 * @param channel channel number of the first channel in the group to perform analysis on
121 * @param coeffs array of pointers to the transformed coefficients
122 * @param wi window information for the channels in the group
124 void (*analyze
)(FFPsyContext
*ctx
, int channel
, const float **coeffs
, const FFPsyWindowInfo
*wi
);
126 void (*end
) (FFPsyContext
*apc
);
130 * Initialize psychoacoustic model.
132 * @param ctx model context
133 * @param avctx codec context
134 * @param num_lens number of possible frame lengths
135 * @param bands scalefactor band lengths for all frame lengths
136 * @param num_bands number of scalefactor bands for all frame lengths
137 * @param num_groups number of channel groups
138 * @param group_map array with # of channels in group - 1, for each group
140 * @return zero if successful, a negative value if not
142 int ff_psy_init(FFPsyContext
*ctx
, AVCodecContext
*avctx
, int num_lens
,
143 const uint8_t **bands
, const int *num_bands
,
144 int num_groups
, const uint8_t *group_map
);
147 * Determine what group a channel belongs to.
149 * @param ctx psymodel context
150 * @param channel channel to locate the group for
152 * @return pointer to the FFPsyChannelGroup this channel belongs to
154 FFPsyChannelGroup
*ff_psy_find_group(FFPsyContext
*ctx
, int channel
);
157 * Cleanup model context at the end.
159 * @param ctx model context
161 void ff_psy_end(FFPsyContext
*ctx
);
164 /**************************************************************************
165 * Audio preprocessing stuff. *
166 * This should be moved into some audio filter eventually. *
167 **************************************************************************/
168 struct FFPsyPreprocessContext
;
171 * psychoacoustic model audio preprocessing initialization
173 struct FFPsyPreprocessContext
*ff_psy_preprocess_init(AVCodecContext
*avctx
);
176 * Preprocess several channel in audio frame in order to compress it better.
178 * @param ctx preprocessing context
179 * @param audio samples to be filtered (in place)
180 * @param channels number of channel to preprocess
182 void ff_psy_preprocess(struct FFPsyPreprocessContext
*ctx
, float **audio
, int channels
);
185 * Cleanup audio preprocessing module.
187 void ff_psy_preprocess_end(struct FFPsyPreprocessContext
*ctx
);
189 #endif /* AVCODEC_PSYMODEL_H */