FFmpeg
sbc.c
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1 /*
2  * Bluetooth low-complexity, subband codec (SBC)
3  *
4  * Copyright (C) 2017 Aurelien Jacobs <aurel@gnuage.org>
5  * Copyright (C) 2012-2013 Intel Corporation
6  * Copyright (C) 2008-2010 Nokia Corporation
7  * Copyright (C) 2004-2010 Marcel Holtmann <marcel@holtmann.org>
8  * Copyright (C) 2004-2005 Henryk Ploetz <henryk@ploetzli.ch>
9  * Copyright (C) 2005-2008 Brad Midgley <bmidgley@xmission.com>
10  *
11  * This file is part of FFmpeg.
12  *
13  * FFmpeg is free software; you can redistribute it and/or
14  * modify it under the terms of the GNU Lesser General Public
15  * License as published by the Free Software Foundation; either
16  * version 2.1 of the License, or (at your option) any later version.
17  *
18  * FFmpeg is distributed in the hope that it will be useful,
19  * but WITHOUT ANY WARRANTY; without even the implied warranty of
20  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
21  * Lesser General Public License for more details.
22  *
23  * You should have received a copy of the GNU Lesser General Public
24  * License along with FFmpeg; if not, write to the Free Software
25  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
26  */
27 
28 /**
29  * @file
30  * SBC common functions for the encoder and decoder
31  */
32 
33 #include "sbc.h"
34 
35 /* A2DP specification: Appendix B, page 69 */
36 static const int sbc_offset4[4][4] = {
37  { -1, 0, 0, 0 },
38  { -2, 0, 0, 1 },
39  { -2, 0, 0, 1 },
40  { -2, 0, 0, 1 }
41 };
42 
43 /* A2DP specification: Appendix B, page 69 */
44 static const int sbc_offset8[4][8] = {
45  { -2, 0, 0, 0, 0, 0, 0, 1 },
46  { -3, 0, 0, 0, 0, 0, 1, 2 },
47  { -4, 0, 0, 0, 0, 0, 1, 2 },
48  { -4, 0, 0, 0, 0, 0, 1, 2 }
49 };
50 
51 /*
52  * Calculates the CRC-8 of the first len bits in data
53  */
54 uint8_t ff_sbc_crc8(const AVCRC *ctx, const uint8_t *data, size_t len)
55 {
56  size_t byte_length = len >> 3;
57  int bit_length = len & 7;
58  uint8_t crc;
59 
60  crc = av_crc(ctx, 0x0F, data, byte_length);
61 
62  if (bit_length) {
63  uint8_t bits = data[byte_length];
64  while (bit_length--) {
65  int8_t mask = bits ^ crc;
66  crc = (crc << 1) ^ ((mask >> 7) & 0x1D);
67  bits <<= 1;
68  }
69  }
70 
71  return crc;
72 }
73 
74 /*
75  * Code straight from the spec to calculate the bits array
76  * Takes a pointer to the frame in question and a pointer to the bits array
77  */
78 void ff_sbc_calculate_bits(const struct sbc_frame *frame, int (*bits)[8])
79 {
80  int subbands = frame->subbands;
81  uint8_t sf = frame->frequency;
82 
83  if (frame->mode == MONO || frame->mode == DUAL_CHANNEL) {
84  int bitneed[2][8], loudness, max_bitneed, bitcount, slicecount, bitslice;
85  int ch, sb;
86 
87  for (ch = 0; ch < frame->channels; ch++) {
88  max_bitneed = 0;
89  if (frame->allocation == SNR) {
90  for (sb = 0; sb < subbands; sb++) {
91  bitneed[ch][sb] = frame->scale_factor[ch][sb];
92  if (bitneed[ch][sb] > max_bitneed)
93  max_bitneed = bitneed[ch][sb];
94  }
95  } else {
96  for (sb = 0; sb < subbands; sb++) {
97  if (frame->scale_factor[ch][sb] == 0)
98  bitneed[ch][sb] = -5;
99  else {
100  if (subbands == 4)
101  loudness = frame->scale_factor[ch][sb] - sbc_offset4[sf][sb];
102  else
103  loudness = frame->scale_factor[ch][sb] - sbc_offset8[sf][sb];
104  if (loudness > 0)
105  bitneed[ch][sb] = loudness / 2;
106  else
107  bitneed[ch][sb] = loudness;
108  }
109  if (bitneed[ch][sb] > max_bitneed)
110  max_bitneed = bitneed[ch][sb];
111  }
112  }
113 
114  bitcount = 0;
115  slicecount = 0;
116  bitslice = max_bitneed + 1;
117  do {
118  bitslice--;
119  bitcount += slicecount;
120  slicecount = 0;
121  for (sb = 0; sb < subbands; sb++) {
122  if ((bitneed[ch][sb] > bitslice + 1) && (bitneed[ch][sb] < bitslice + 16))
123  slicecount++;
124  else if (bitneed[ch][sb] == bitslice + 1)
125  slicecount += 2;
126  }
127  } while (bitcount + slicecount < frame->bitpool);
128 
129  if (bitcount + slicecount == frame->bitpool) {
130  bitcount += slicecount;
131  bitslice--;
132  }
133 
134  for (sb = 0; sb < subbands; sb++) {
135  if (bitneed[ch][sb] < bitslice + 2)
136  bits[ch][sb] = 0;
137  else {
138  bits[ch][sb] = bitneed[ch][sb] - bitslice;
139  if (bits[ch][sb] > 16)
140  bits[ch][sb] = 16;
141  }
142  }
143 
144  for (sb = 0; bitcount < frame->bitpool &&
145  sb < subbands; sb++) {
146  if ((bits[ch][sb] >= 2) && (bits[ch][sb] < 16)) {
147  bits[ch][sb]++;
148  bitcount++;
149  } else if ((bitneed[ch][sb] == bitslice + 1) && (frame->bitpool > bitcount + 1)) {
150  bits[ch][sb] = 2;
151  bitcount += 2;
152  }
153  }
154 
155  for (sb = 0; bitcount < frame->bitpool &&
156  sb < subbands; sb++) {
157  if (bits[ch][sb] < 16) {
158  bits[ch][sb]++;
159  bitcount++;
160  }
161  }
162 
163  }
164 
165  } else if (frame->mode == STEREO || frame->mode == JOINT_STEREO) {
166  int bitneed[2][8], loudness, max_bitneed, bitcount, slicecount, bitslice;
167  int ch, sb;
168 
169  max_bitneed = 0;
170  if (frame->allocation == SNR) {
171  for (ch = 0; ch < 2; ch++) {
172  for (sb = 0; sb < subbands; sb++) {
173  bitneed[ch][sb] = frame->scale_factor[ch][sb];
174  if (bitneed[ch][sb] > max_bitneed)
175  max_bitneed = bitneed[ch][sb];
176  }
177  }
178  } else {
179  for (ch = 0; ch < 2; ch++) {
180  for (sb = 0; sb < subbands; sb++) {
181  if (frame->scale_factor[ch][sb] == 0)
182  bitneed[ch][sb] = -5;
183  else {
184  if (subbands == 4)
185  loudness = frame->scale_factor[ch][sb] - sbc_offset4[sf][sb];
186  else
187  loudness = frame->scale_factor[ch][sb] - sbc_offset8[sf][sb];
188  if (loudness > 0)
189  bitneed[ch][sb] = loudness / 2;
190  else
191  bitneed[ch][sb] = loudness;
192  }
193  if (bitneed[ch][sb] > max_bitneed)
194  max_bitneed = bitneed[ch][sb];
195  }
196  }
197  }
198 
199  bitcount = 0;
200  slicecount = 0;
201  bitslice = max_bitneed + 1;
202  do {
203  bitslice--;
204  bitcount += slicecount;
205  slicecount = 0;
206  for (ch = 0; ch < 2; ch++) {
207  for (sb = 0; sb < subbands; sb++) {
208  if ((bitneed[ch][sb] > bitslice + 1) && (bitneed[ch][sb] < bitslice + 16))
209  slicecount++;
210  else if (bitneed[ch][sb] == bitslice + 1)
211  slicecount += 2;
212  }
213  }
214  } while (bitcount + slicecount < frame->bitpool);
215 
216  if (bitcount + slicecount == frame->bitpool) {
217  bitcount += slicecount;
218  bitslice--;
219  }
220 
221  for (ch = 0; ch < 2; ch++) {
222  for (sb = 0; sb < subbands; sb++) {
223  if (bitneed[ch][sb] < bitslice + 2) {
224  bits[ch][sb] = 0;
225  } else {
226  bits[ch][sb] = bitneed[ch][sb] - bitslice;
227  if (bits[ch][sb] > 16)
228  bits[ch][sb] = 16;
229  }
230  }
231  }
232 
233  ch = 0;
234  sb = 0;
235  while (bitcount < frame->bitpool) {
236  if ((bits[ch][sb] >= 2) && (bits[ch][sb] < 16)) {
237  bits[ch][sb]++;
238  bitcount++;
239  } else if ((bitneed[ch][sb] == bitslice + 1) && (frame->bitpool > bitcount + 1)) {
240  bits[ch][sb] = 2;
241  bitcount += 2;
242  }
243  if (ch == 1) {
244  ch = 0;
245  sb++;
246  if (sb >= subbands)
247  break;
248  } else
249  ch = 1;
250  }
251 
252  ch = 0;
253  sb = 0;
254  while (bitcount < frame->bitpool) {
255  if (bits[ch][sb] < 16) {
256  bits[ch][sb]++;
257  bitcount++;
258  }
259  if (ch == 1) {
260  ch = 0;
261  sb++;
262  if (sb >= subbands)
263  break;
264  } else
265  ch = 1;
266  }
267 
268  }
269 
270 }
JOINT_STEREO
#define JOINT_STEREO
Definition: atrac3.c:58
AVCRC
uint32_t AVCRC
Definition: crc.h:46
data
const char data[16]
Definition: mxf.c:148
STEREO
#define STEREO
Definition: cook.c:64
subbands
subbands
Definition: aptx.h:37
AVFrame::channels
attribute_deprecated int channels
number of audio channels, only used for audio.
Definition: frame.h:731
mask
static const uint16_t mask[17]
Definition: lzw.c:38
bits
uint8_t bits
Definition: vp3data.h:128
ctx
AVFormatContext * ctx
Definition: movenc.c:48
frame
static AVFrame * frame
Definition: demux_decode.c:54
sbc.h
sbc_frame
Definition: sbc.h:84
sbc_offset8
static const int sbc_offset8[4][8]
Definition: sbc.c:44
len
int len
Definition: vorbis_enc_data.h:426
ff_sbc_crc8
uint8_t ff_sbc_crc8(const AVCRC *ctx, const uint8_t *data, size_t len)
Definition: sbc.c:54
MONO
#define MONO
Definition: cook.c:63
sbc_offset4
static const int sbc_offset4[4][4]
Definition: sbc.c:36
av_crc
uint32_t av_crc(const AVCRC *ctx, uint32_t crc, const uint8_t *buffer, size_t length)
Calculate the CRC of a block.
Definition: crc.c:392
ff_sbc_calculate_bits
void ff_sbc_calculate_bits(const struct sbc_frame *frame, int(*bits)[8])
Definition: sbc.c:78
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