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 "mathops.h"
29 #include "audio_frame_queue.h"
30 
31 
32 enum channels {
33     LEFT,
34     RIGHT,
35     NB_CHANNELS
36 };
37 
38 enum subbands {
39     LF,  // Low Frequency (0-5.5 kHz)
40     MLF, // Medium-Low Frequency (5.5-11kHz)
41     MHF, // Medium-High Frequency (11-16.5kHz)
42     HF,  // High Frequency (16.5-22kHz)
43     NB_SUBBANDS
44 };
45 
46 #define NB_FILTERS 2
47 #define FILTER_TAPS 16
48 
49 typedef struct {
50     int pos;
51     int32_t buffer[2*FILTER_TAPS];
52 } FilterSignal;
53 
54 typedef struct {
55     FilterSignal outer_filter_signal[NB_FILTERS];
56     FilterSignal inner_filter_signal[NB_FILTERS][NB_FILTERS];
57 } QMFAnalysis;
58 
59 typedef struct {
60     int32_t quantized_sample;
61     int32_t quantized_sample_parity_change;
62     int32_t error;
63 } Quantize;
64 
65 typedef struct {
66     int32_t quantization_factor;
67     int32_t factor_select;
68     int32_t reconstructed_difference;
69 } InvertQuantize;
70 
71 typedef struct {
72     int32_t prev_sign[2];
73     int32_t s_weight[2];
74     int32_t d_weight[24];
75     int32_t pos;
76     int32_t reconstructed_differences[48];
77     int32_t previous_reconstructed_sample;
78     int32_t predicted_difference;
79     int32_t predicted_sample;
80 } Prediction;
81 
82 typedef struct {
83     int32_t codeword_history;
84     int32_t dither_parity;
85     int32_t dither[NB_SUBBANDS];
86 
87     QMFAnalysis qmf;
88     Quantize quantize[NB_SUBBANDS];
89     InvertQuantize invert_quantize[NB_SUBBANDS];
90     Prediction prediction[NB_SUBBANDS];
91 } Channel;
92 
93 typedef struct {
94     int hd;
95     int block_size;
96     int32_t sync_idx;
97     Channel channels[NB_CHANNELS];
98     AudioFrameQueue afq;
99 } AptXContext;
100 
101 typedef const struct {
102     const int32_t *quantize_intervals;
103     const int32_t *invert_quantize_dither_factors;
104     const int32_t *quantize_dither_factors;
105     const int16_t *quantize_factor_select_offset;
106     int tables_size;
107     int32_t factor_max;
108     int32_t prediction_order;
109 } ConstTables;
110 
111 extern ConstTables ff_aptx_quant_tables[2][NB_SUBBANDS];
112 
113 /* Rounded right shift with optionnal clipping */
114 #define RSHIFT_SIZE(size)                                                     \
115 av_always_inline                                                              \
116 static int##size##_t rshift##size(int##size##_t value, int shift)             \
117 {                                                                             \
118     int##size##_t rounding = (int##size##_t)1 << (shift - 1);                 \
119     int##size##_t mask = ((int##size##_t)1 << (shift + 1)) - 1;               \
120     return ((value + rounding) >> shift) - ((value & mask) == rounding);      \
121 }                                                                             \
122 av_always_inline                                                              \
123 static int##size##_t rshift##size##_clip24(int##size##_t value, int shift)    \
124 {                                                                             \
125     return av_clip_intp2(rshift##size(value, shift), 23);                     \
126 }
127 RSHIFT_SIZE(32)
128 RSHIFT_SIZE(64)
129 
130 /*
131  * Convolution filter coefficients for the outer QMF of the QMF tree.
132  * The 2 sets are a mirror of each other.
133  */
134 static const int32_t aptx_qmf_outer_coeffs[NB_FILTERS][FILTER_TAPS] = {
135     {
136         730, -413, -9611, 43626, -121026, 269973, -585547, 2801966,
137         697128, -160481, 27611, 8478, -10043, 3511, 688, -897,
138     },
139     {
140         -897, 688, 3511, -10043, 8478, 27611, -160481, 697128,
141         2801966, -585547, 269973, -121026, 43626, -9611, -413, 730,
142     },
143 };
144 
145 /*
146  * Convolution filter coefficients for the inner QMF of the QMF tree.
147  * The 2 sets are a mirror of each other.
148  */
149 static const int32_t aptx_qmf_inner_coeffs[NB_FILTERS][FILTER_TAPS] = {
150     {
151        1033, -584, -13592, 61697, -171156, 381799, -828088, 3962579,
152        985888, -226954, 39048, 11990, -14203, 4966, 973, -1268,
153     },
154     {
155       -1268, 973, 4966, -14203, 11990, 39048, -226954, 985888,
156       3962579, -828088, 381799, -171156, 61697, -13592, -584, 1033,
157     },
158 };
159 
160 /*
161  * Push one sample into a circular signal buffer.
162  */
163 av_always_inline
aptx_qmf_filter_signal_push(FilterSignal *signal, int32_t sample)164 static void aptx_qmf_filter_signal_push(FilterSignal *signal, int32_t sample)
165 {
166     signal->buffer[signal->pos            ] = sample;
167     signal->buffer[signal->pos+FILTER_TAPS] = sample;
168     signal->pos = (signal->pos + 1) & (FILTER_TAPS - 1);
169 }
170 
171 /*
172  * Compute the convolution of the signal with the coefficients, and reduce
173  * to 24 bits by applying the specified right shifting.
174  */
175 av_always_inline
aptx_qmf_convolution(FilterSignal *signal, const int32_t coeffs[FILTER_TAPS], int shift)176 static int32_t aptx_qmf_convolution(FilterSignal *signal,
177                                     const int32_t coeffs[FILTER_TAPS],
178                                     int shift)
179 {
180     int32_t *sig = &signal->buffer[signal->pos];
181     int64_t e = 0;
182     int i;
183 
184     for (i = 0; i < FILTER_TAPS; i++)
185         e += MUL64(sig[i], coeffs[i]);
186 
187     return rshift64_clip24(e, shift);
188 }
189 
aptx_quantized_parity(Channel *channel)190 static inline int32_t aptx_quantized_parity(Channel *channel)
191 {
192     int32_t parity = channel->dither_parity;
193     int subband;
194 
195     for (subband = 0; subband < NB_SUBBANDS; subband++)
196         parity ^= channel->quantize[subband].quantized_sample;
197 
198     return parity & 1;
199 }
200 
201 /* For each sample, ensure that the parity of all subbands of all channels
202  * is 0 except once every 8 samples where the parity is forced to 1. */
aptx_check_parity(Channel channels[NB_CHANNELS], int32_t *idx)203 static inline int aptx_check_parity(Channel channels[NB_CHANNELS], int32_t *idx)
204 {
205     int32_t parity = aptx_quantized_parity(&channels[LEFT])
206                    ^ aptx_quantized_parity(&channels[RIGHT]);
207 
208     int eighth = *idx == 7;
209     *idx = (*idx + 1) & 7;
210 
211     return parity ^ eighth;
212 }
213 
214 void ff_aptx_invert_quantize_and_prediction(Channel *channel, int hd);
215 void ff_aptx_generate_dither(Channel *channel);
216 
217 int ff_aptx_init(AVCodecContext *avctx);
218 
219 #endif /* AVCODEC_APTX_H */
220