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
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 /* cutoff for VBR is purposely increased, since LP filtering actually
33 * hinders VBR performance rather than the opposite
34 */
35 #define AAC_CUTOFF_FROM_BITRATE(bit_rate,channels,sample_rate) (bit_rate ? FFMIN3(FFMIN3( \
36 FFMAX(bit_rate/channels/5, bit_rate/channels*15/32 - 5500), \
37 3000 + bit_rate/channels/4, \
38 12000 + bit_rate/channels/16), \
39 22000, \
40 sample_rate / 2): (sample_rate / 2))
41 #define AAC_CUTOFF(s) ( \
42 (s->flags & AV_CODEC_FLAG_QSCALE) \
43 ? s->sample_rate / 2 \
44 : AAC_CUTOFF_FROM_BITRATE(s->bit_rate, s->ch_layout.nb_channels, s->sample_rate) \
45 )
46
47 /**
48 * single band psychoacoustic information
49 */
54 float spread;
/* Energy spread over the band */
56
57 /**
58 * single channel psychoacoustic information
59 */
62 float entropy;
///< total PE for this channel
64
65 /**
66 * psychoacoustic information for an arbitrary group of channels
67 */
70 uint8_t
num_ch;
///< number of channels in this group
73
74 /**
75 * windowing related information
76 */
78 int window_type[3];
///< window type (short/long/transitional, etc.) - current, previous and next
81 int grouping[8];
///< window grouping (for e.g. AAC)
82 float clipping[8];
///< maximum absolute normalized intensity in the given window for clip avoidance
83 int *
window_sizes;
///< sequence of window sizes inside one frame (for eg. WMA)
85
86 /**
87 * context used by psychoacoustic model
88 */
92
96 int cutoff;
///< lowpass frequency cutoff for analysis
97
98 uint8_t **
bands;
///< scalefactor band sizes for possible frame sizes
99 int *
num_bands;
///< number of scalefactor bands for possible frame sizes
101
102 struct {
103 int size;
///< size of the bitresevoir in bits
104 int bits;
///< number of bits used in the bitresevoir
105 int alloc;
///< number of bits allocated by the psy, or -1 if no allocation was done
107
110
111 /**
112 * codec-specific psychoacoustic model implementation
113 */
117
118 /**
119 * Suggest window sequence for channel.
120 *
121 * @param ctx model context
122 * @param audio samples for the current frame
123 * @param la lookahead samples (NULL when unavailable)
124 * @param channel number of channel element to analyze
125 * @param prev_type previous window type
126 *
127 * @return suggested window information in a structure
128 */
130
131 /**
132 * Perform psychoacoustic analysis and set band info (threshold, energy) for a group of channels.
133 *
134 * @param ctx model context
135 * @param channel channel number of the first channel in the group to perform analysis on
136 * @param coeffs array of pointers to the transformed coefficients
137 * @param wi window information for the channels in the group
138 */
140
143
144 /**
145 * Initialize psychoacoustic model.
146 *
147 * @param ctx model context
148 * @param avctx codec context
149 * @param num_lens number of possible frame lengths
150 * @param bands scalefactor band lengths for all frame lengths
151 * @param num_bands number of scalefactor bands for all frame lengths
152 * @param num_groups number of channel groups
153 * @param group_map array with # of channels in group - 1, for each group
154 *
155 * @return zero if successful, a negative value if not
156 */
158 const uint8_t **
bands,
const int *num_bands,
159 int num_groups, const uint8_t *group_map);
160
161 /**
162 * Determine what group a channel belongs to.
163 *
164 * @param ctx psymodel context
165 * @param channel channel to locate the group for
166 *
167 * @return pointer to the FFPsyChannelGroup this channel belongs to
168 */
170
171 /**
172 * Cleanup model context at the end.
173 *
174 * @param ctx model context
175 */
177
178
179 /**************************************************************************
180 * Audio preprocessing stuff. *
181 * This should be moved into some audio filter eventually. *
182 **************************************************************************/
184
185 /**
186 * psychoacoustic model audio preprocessing initialization
187 */
189
190 /**
191 * Preprocess several channel in audio frame in order to compress it better.
192 *
193 * @param ctx preprocessing context
194 * @param audio samples to be filtered (in place)
195 * @param channels number of channel to preprocess
196 */
198
199 /**
200 * Cleanup audio preprocessing module.
201 */
203
204 #endif /* AVCODEC_PSYMODEL_H */