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acelp_pitch_delay.h
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1 /*
2  * gain code, gain pitch and pitch delay decoding
3  *
4  * Copyright (c) 2008 Vladimir Voroshilov
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_ACELP_PITCH_DELAY_H
24 #define AVCODEC_ACELP_PITCH_DELAY_H
25 
26 #include <stdint.h>
27 
28 #include "audiodsp.h"
29 
30 #define PITCH_DELAY_MIN 20
31 #define PITCH_DELAY_MAX 143
32 
33 /**
34  * @brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3
35  * resolution.
36  * @param ac_index adaptive codebook index (8 bits)
37  *
38  * @return pitch delay in 1/3 units
39  *
40  * Pitch delay is coded:
41  * with 1/3 resolution, 19 < pitch_delay < 85
42  * integers only, 85 <= pitch_delay <= 143
43  */
44 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index);
45 
46 /**
47  * @brief Decode pitch delay of the second subframe encoded by 5 or 6 bits
48  * with 1/3 precision.
49  * @param ac_index adaptive codebook index (5 or 6 bits)
50  * @param pitch_delay_min lower bound (integer) of pitch delay interval
51  * for second subframe
52  *
53  * @return pitch delay in 1/3 units
54  *
55  * Pitch delay is coded:
56  * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
57  *
58  * @remark The routine is used in G.729 @@8k, AMR @@10.2k, AMR @@7.95k,
59  * AMR @@7.4k for the second subframe.
60  */
62  int ac_index,
63  int pitch_delay_min);
64 
65 /**
66  * @brief Decode pitch delay with 1/3 precision.
67  * @param ac_index adaptive codebook index (4 bits)
68  * @param pitch_delay_min lower bound (integer) of pitch delay interval for
69  * second subframe
70  *
71  * @return pitch delay in 1/3 units
72  *
73  * Pitch delay is coded:
74  * integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2
75  * with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1
76  * integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5
77  *
78  * @remark The routine is used in G.729 @@6.4k, AMR @@6.7k, AMR @@5.9k,
79  * AMR @@5.15k, AMR @@4.75k for the second subframe.
80  */
82  int ac_index,
83  int pitch_delay_min);
84 
85 /**
86  * @brief Decode pitch delay of the first subframe encoded by 9 bits
87  * with 1/6 precision.
88  * @param ac_index adaptive codebook index (9 bits)
89  *
90  * @return pitch delay in 1/6 units
91  *
92  * Pitch delay is coded:
93  * with 1/6 resolution, 17 < pitch_delay < 95
94  * integers only, 95 <= pitch_delay <= 143
95  *
96  * @remark The routine is used in AMR @@12.2k for the first and third subframes.
97  */
98 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index);
99 
100 /**
101  * @brief Decode pitch delay of the second subframe encoded by 6 bits
102  * with 1/6 precision.
103  * @param ac_index adaptive codebook index (6 bits)
104  * @param pitch_delay_min lower bound (integer) of pitch delay interval for
105  * second subframe
106  *
107  * @return pitch delay in 1/6 units
108  *
109  * Pitch delay is coded:
110  * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
111  *
112  * @remark The routine is used in AMR @@12.2k for the second and fourth subframes.
113  */
115  int ac_index,
116  int pitch_delay_min);
117 
118 /**
119  * @brief Update past quantized energies
120  * @param[in,out] quant_energy past quantized energies (5.10)
121  * @param gain_corr_factor gain correction factor
122  * @param log2_ma_pred_order log2() of MA prediction order
123  * @param erasure frame erasure flag
124  *
125  * If frame erasure flag is not equal to zero, memory is updated with
126  * averaged energy, attenuated by 4dB:
127  * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order
128  *
129  * In normal mode memory is updated with
130  * Er - Ep = 20 * log10(gain_corr_factor)
131  *
132  * @remark The routine is used in G.729 and AMR (all modes).
133  */
135  int16_t* quant_energy,
136  int gain_corr_factor,
137  int log2_ma_pred_order,
138  int erasure);
139 
140 /**
141  * @brief Decode the adaptive codebook gain and add
142  * correction (4.1.5 and 3.9.1 of G.729).
143  * @param adsp initialized audio DSP context
144  * @param gain_corr_factor gain correction factor (2.13)
145  * @param fc_v fixed-codebook vector (2.13)
146  * @param mr_energy mean innovation energy and fixed-point correction (7.13)
147  * @param[in,out] quant_energy past quantized energies (5.10)
148  * @param subframe_size length of subframe
149  *
150  * @return quantized fixed-codebook gain (14.1)
151  *
152  * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
153  *
154  * Em - mean innovation energy (dB, constant, depends on decoding algorithm)
155  * Ep - mean-removed predicted energy (dB)
156  * Er - mean-removed innovation energy (dB)
157  * Ei - mean energy of the fixed-codebook contribution (dB)
158  * N - subframe_size
159  * M - MA (Moving Average) prediction order
160  * gc - fixed-codebook gain
161  * gc_p - predicted fixed-codebook gain
162  *
163  * Fixed codebook gain is computed using predicted gain gc_p and
164  * correction factor gain_corr_factor as shown below:
165  *
166  * gc = gc_p * gain_corr_factor
167  *
168  * The predicted fixed codebook gain gc_p is found by predicting
169  * the energy of the fixed-codebook contribution from the energy
170  * of previous fixed-codebook contributions.
171  *
172  * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
173  *
174  * Ei = 10log(mean)
175  *
176  * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
177  *
178  * Replacing Er with Ep and gc with gc_p we will receive:
179  *
180  * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
181  *
182  * and from above:
183  *
184  * gc_p = 10^((Ep - Ei + Em) / 20)
185  *
186  * Ep is predicted using past energies and prediction coefficients:
187  *
188  * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
189  *
190  * gc_p in fixed-point arithmetic is calculated as following:
191  *
192  * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } =
193  * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26
194  *
195  * Ei = 10log(mean) = -10log(N) - 10log(2^26) +
196  * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
197  *
198  * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -
199  * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) =
200  * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
201  *
202  * gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
203  * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
204  *
205  * where
206  *
207  * mr_energy = Em + 10log(N) + 10log(2^26)
208  *
209  * @remark The routine is used in G.729 and AMR (all modes).
210  */
212  AudioDSPContext *adsp,
213  int gain_corr_factor,
214  const int16_t* fc_v,
215  int mr_energy,
216  const int16_t* quant_energy,
217  const int16_t* ma_prediction_coeff,
218  int subframe_size,
219  int max_pred_order);
220 
221 /**
222  * Calculate fixed gain (part of section 6.1.3 of AMR spec)
223  *
224  * @param fixed_gain_factor gain correction factor
225  * @param fixed_mean_energy mean decoded algebraic codebook vector energy
226  * @param prediction_error vector of the quantified predictor errors of
227  * the four previous subframes. It is updated by this function.
228  * @param energy_mean desired mean innovation energy
229  * @param pred_table table of four moving average coefficients
230  */
231 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
232  float *prediction_error, float energy_mean,
233  const float *pred_table);
234 
235 
236 /**
237  * Decode the adaptive codebook index to the integer and fractional parts
238  * of the pitch lag for one subframe at 1/3 fractional precision.
239  *
240  * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1.
241  *
242  * @param lag_int integer part of pitch lag of the current subframe
243  * @param lag_frac fractional part of pitch lag of the current subframe
244  * @param pitch_index parsed adaptive codebook (pitch) index
245  * @param prev_lag_int integer part of pitch lag for the previous subframe
246  * @param subframe current subframe number
247  * @param third_as_first treat the third frame the same way as the first
248  */
249 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
250  const int prev_lag_int, const int subframe,
251  int third_as_first, int resolution);
252 
253 #endif /* AVCODEC_ACELP_PITCH_DELAY_H */