FFmpeg: libavcodec/psymodel.h Source File

FFmpeg
psymodel.h
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1 /*
2  * audio encoder psychoacoustic model
3  * Copyright (C) 2008 Konstantin Shishkov
4  *
5  * This file is part of FFmpeg.
6  *
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
10  * version 2.1 of the License, or (at your option) any later version.
11  *
12  * FFmpeg is distributed in the hope that it will be useful,
13  * but WITHOUT ANY WARRANTY; without even the implied warranty of
14  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
15  * Lesser General Public License for more details.
16  *
17  * You should have received a copy of the GNU Lesser General Public
18  * License along with FFmpeg; if not, write to the Free Software
19  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
20  */
21 
22 #ifndef AVCODEC_PSYMODEL_H
23 #define AVCODEC_PSYMODEL_H
24 
25 #include "avcodec.h"
26 
27 /** maximum possible number of bands */
28  #define PSY_MAX_BANDS 128
29 /** maximum number of channels */
30  #define PSY_MAX_CHANS 20
31 
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))
33 
34 /**
35  * single band psychoacoustic information
36  */
37  typedef struct FFPsyBand {
38   int bits;
39   float energy;
40   float threshold;
41   float distortion;
42   float perceptual_weight;
43 } FFPsyBand;
44 
45 /**
46  * single channel psychoacoustic information
47  */
48  typedef struct FFPsyChannel {
49   FFPsyBand psy_bands[PSY_MAX_BANDS]; ///< channel bands information
50   float entropy; ///< total PE for this channel
51 } FFPsyChannel;
52 
53 /**
54  * psychoacoustic information for an arbitrary group of channels
55  */
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
60 } FFPsyChannelGroup;
61 
62 /**
63  * windowing related information
64  */
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)
71 } FFPsyWindowInfo;
72 
73 /**
74  * context used by psychoacoustic model
75  */
76  typedef struct FFPsyContext {
77   AVCodecContext *avctx; ///< encoder context
78   const struct FFPsyModel *model; ///< encoder-specific model functions
79 
80   FFPsyChannel *ch; ///< single channel information
81   FFPsyChannelGroup *group; ///< channel group information
82   int num_groups; ///< number of channel groups
83 
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
87 
88  struct {
89   int size; ///< size of the bitresevoir in bits
90   int bits; ///< number of bits used in the bitresevoir
91  } bitres;
92 
93   void* model_priv_data; ///< psychoacoustic model implementation private data
94 } FFPsyContext;
95 
96 /**
97  * codec-specific psychoacoustic model implementation
98  */
99  typedef struct FFPsyModel {
100   const char *name;
101   int (*init) (FFPsyContext *apc);
102 
103  /**
104  * Suggest window sequence for channel.
105  *
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
111  *
112  * @return suggested window information in a structure
113  */
114   FFPsyWindowInfo (*window)(FFPsyContext *ctx, const float *audio, const float *la, int channel, int prev_type);
115 
116  /**
117  * Perform psychoacoustic analysis and set band info (threshold, energy) for a group of channels.
118  *
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
123  */
124   void (*analyze)(FFPsyContext *ctx, int channel, const float **coeffs, const FFPsyWindowInfo *wi);
125 
126   void (*end) (FFPsyContext *apc);
127 } FFPsyModel;
128 
129 /**
130  * Initialize psychoacoustic model.
131  *
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
139  *
140  * @return zero if successful, a negative value if not
141  */
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);
145 
146 /**
147  * Determine what group a channel belongs to.
148  *
149  * @param ctx psymodel context
150  * @param channel channel to locate the group for
151  *
152  * @return pointer to the FFPsyChannelGroup this channel belongs to
153  */
154 FFPsyChannelGroup *ff_psy_find_group(FFPsyContext *ctx, int channel);
155 
156 /**
157  * Cleanup model context at the end.
158  *
159  * @param ctx model context
160  */
161 void ff_psy_end(FFPsyContext *ctx);
162 
163 
164 /**************************************************************************
165  * Audio preprocessing stuff. *
166  * This should be moved into some audio filter eventually. *
167  **************************************************************************/
168 struct FFPsyPreprocessContext;
169 
170 /**
171  * psychoacoustic model audio preprocessing initialization
172  */
173 struct FFPsyPreprocessContext *ff_psy_preprocess_init(AVCodecContext *avctx);
174 
175 /**
176  * Preprocess several channel in audio frame in order to compress it better.
177  *
178  * @param ctx preprocessing context
179  * @param audio samples to be filtered (in place)
180  * @param channels number of channel to preprocess
181  */
182 void ff_psy_preprocess(struct FFPsyPreprocessContext *ctx, float **audio, int channels);
183 
184 /**
185  * Cleanup audio preprocessing module.
186  */
187 void ff_psy_preprocess_end(struct FFPsyPreprocessContext *ctx);
188 
189 #endif /* AVCODEC_PSYMODEL_H */
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