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