1 /*
2 * Audio Processing Technology codec for Bluetooth (aptX)
3 *
4 * Copyright (C) 2017 Aurelien Jacobs <aurel@gnuage.org>
5 *
6 * This file is part of FFmpeg.
7 *
8 * FFmpeg is free software; you can redistribute it and/or
9 * modify it under the terms of the GNU Lesser General Public
10 * License as published by the Free Software Foundation; either
11 * version 2.1 of the License, or (at your option) any later version.
12 *
13 * FFmpeg is distributed in the hope that it will be useful,
14 * but WITHOUT ANY WARRANTY; without even the implied warranty of
15 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
16 * Lesser General Public License for more details.
17 *
18 * You should have received a copy of the GNU Lesser General Public
19 * License along with FFmpeg; if not, write to the Free Software
20 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
21 */
22
23 #ifndef AVCODEC_APTX_H
24 #define AVCODEC_APTX_H
25
26 #include "libavutil/intreadwrite.h"
27 #include "avcodec.h"
28 #include "internal.h"
29 #include "mathops.h"
30 #include "audio_frame_queue.h"
31
32
33 enum channels {
34 LEFT,
35 RIGHT,
36 NB_CHANNELS
37 };
38
39 enum subbands {
40 LF, // Low Frequency (0-5.5 kHz)
41 MLF, // Medium-Low Frequency (5.5-11kHz)
42 MHF, // Medium-High Frequency (11-16.5kHz)
43 HF, // High Frequency (16.5-22kHz)
44 NB_SUBBANDS
45 };
46
47 #define NB_FILTERS 2
48 #define FILTER_TAPS 16
49
50 typedef struct {
51 int pos;
52 int32_t buffer[2*FILTER_TAPS];
53 } FilterSignal;
54
55 typedef struct {
56 FilterSignal outer_filter_signal[NB_FILTERS];
57 FilterSignal inner_filter_signal[NB_FILTERS][NB_FILTERS];
58 } QMFAnalysis;
59
60 typedef struct {
61 int32_t quantized_sample;
62 int32_t quantized_sample_parity_change;
63 int32_t error;
64 } Quantize;
65
66 typedef struct {
67 int32_t quantization_factor;
68 int32_t factor_select;
69 int32_t reconstructed_difference;
70 } InvertQuantize;
71
72 typedef struct {
73 int32_t prev_sign[2];
74 int32_t s_weight[2];
75 int32_t d_weight[24];
76 int32_t pos;
77 int32_t reconstructed_differences[48];
78 int32_t previous_reconstructed_sample;
79 int32_t predicted_difference;
80 int32_t predicted_sample;
81 } Prediction;
82
83 typedef struct {
84 int32_t codeword_history;
85 int32_t dither_parity;
86 int32_t dither[NB_SUBBANDS];
87
88 QMFAnalysis qmf;
89 Quantize quantize[NB_SUBBANDS];
90 InvertQuantize invert_quantize[NB_SUBBANDS];
91 Prediction prediction[NB_SUBBANDS];
92 } Channel;
93
94 typedef struct {
95 int hd;
96 int block_size;
97 int32_t sync_idx;
98 Channel channels[NB_CHANNELS];
99 AudioFrameQueue afq;
100 } AptXContext;
101
102 typedef const struct {
103 const int32_t *quantize_intervals;
104 const int32_t *invert_quantize_dither_factors;
105 const int32_t *quantize_dither_factors;
106 const int16_t *quantize_factor_select_offset;
107 int tables_size;
108 int32_t factor_max;
109 int32_t prediction_order;
110 } ConstTables;
111
112 extern ConstTables ff_aptx_quant_tables[2][NB_SUBBANDS];
113
114 /* Rounded right shift with optionnal clipping */
115 #define RSHIFT_SIZE(size) \
116 av_always_inline \
117 static int##size##_t rshift##size(int##size##_t value, int shift) \
118 { \
119 int##size##_t rounding = (int##size##_t)1 << (shift - 1); \
120 int##size##_t mask = ((int##size##_t)1 << (shift + 1)) - 1; \
121 return ((value + rounding) >> shift) - ((value & mask) == rounding); \
122 } \
123 av_always_inline \
124 static int##size##_t rshift##size##_clip24(int##size##_t value, int shift) \
125 { \
126 return av_clip_intp2(rshift##size(value, shift), 23); \
127 }
128 RSHIFT_SIZE(32)
129 RSHIFT_SIZE(64)
130
131 /*
132 * Convolution filter coefficients for the outer QMF of the QMF tree.
133 * The 2 sets are a mirror of each other.
134 */
135 static const int32_t aptx_qmf_outer_coeffs[NB_FILTERS][FILTER_TAPS] = {
136 {
137 730, -413, -9611, 43626, -121026, 269973, -585547, 2801966,
138 697128, -160481, 27611, 8478, -10043, 3511, 688, -897,
139 },
140 {
141 -897, 688, 3511, -10043, 8478, 27611, -160481, 697128,
142 2801966, -585547, 269973, -121026, 43626, -9611, -413, 730,
143 },
144 };
145
146 /*
147 * Convolution filter coefficients for the inner QMF of the QMF tree.
148 * The 2 sets are a mirror of each other.
149 */
150 static const int32_t aptx_qmf_inner_coeffs[NB_FILTERS][FILTER_TAPS] = {
151 {
152 1033, -584, -13592, 61697, -171156, 381799, -828088, 3962579,
153 985888, -226954, 39048, 11990, -14203, 4966, 973, -1268,
154 },
155 {
156 -1268, 973, 4966, -14203, 11990, 39048, -226954, 985888,
157 3962579, -828088, 381799, -171156, 61697, -13592, -584, 1033,
158 },
159 };
160
161 /*
162 * Push one sample into a circular signal buffer.
163 */
164 av_always_inline
aptx_qmf_filter_signal_push(FilterSignal * signal,int32_t sample)165 static void aptx_qmf_filter_signal_push(FilterSignal *signal, int32_t sample)
166 {
167 signal->buffer[signal->pos ] = sample;
168 signal->buffer[signal->pos+FILTER_TAPS] = sample;
169 signal->pos = (signal->pos + 1) & (FILTER_TAPS - 1);
170 }
171
172 /*
173 * Compute the convolution of the signal with the coefficients, and reduce
174 * to 24 bits by applying the specified right shifting.
175 */
176 av_always_inline
aptx_qmf_convolution(FilterSignal * signal,const int32_t coeffs[FILTER_TAPS],int shift)177 static int32_t aptx_qmf_convolution(FilterSignal *signal,
178 const int32_t coeffs[FILTER_TAPS],
179 int shift)
180 {
181 int32_t *sig = &signal->buffer[signal->pos];
182 int64_t e = 0;
183 int i;
184
185 for (i = 0; i < FILTER_TAPS; i++)
186 e += MUL64(sig[i], coeffs[i]);
187
188 return rshift64_clip24(e, shift);
189 }
190
aptx_quantized_parity(Channel * channel)191 static inline int32_t aptx_quantized_parity(Channel *channel)
192 {
193 int32_t parity = channel->dither_parity;
194 int subband;
195
196 for (subband = 0; subband < NB_SUBBANDS; subband++)
197 parity ^= channel->quantize[subband].quantized_sample;
198
199 return parity & 1;
200 }
201
202 /* For each sample, ensure that the parity of all subbands of all channels
203 * is 0 except once every 8 samples where the parity is forced to 1. */
aptx_check_parity(Channel channels[NB_CHANNELS],int32_t * idx)204 static inline int aptx_check_parity(Channel channels[NB_CHANNELS], int32_t *idx)
205 {
206 int32_t parity = aptx_quantized_parity(&channels[LEFT])
207 ^ aptx_quantized_parity(&channels[RIGHT]);
208
209 int eighth = *idx == 7;
210 *idx = (*idx + 1) & 7;
211
212 return parity ^ eighth;
213 }
214
215 void ff_aptx_invert_quantize_and_prediction(Channel *channel, int hd);
216 void ff_aptx_generate_dither(Channel *channel);
217
218 int ff_aptx_init(AVCodecContext *avctx);
219
220 #endif /* AVCODEC_APTX_H */
221