FFmpeg  4.4.4
acelp_pitch_delay.h
Go to the documentation of this file.
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 static inline int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
45 {
46  ac_index += 58;
47  if (ac_index > 254)
48  ac_index = 3 * ac_index - 510;
49  return ac_index;
50 }
51 
52 /**
53  * @brief Decode pitch delay of the second subframe encoded by 5 or 6 bits
54  * with 1/3 precision.
55  * @param ac_index adaptive codebook index (5 or 6 bits)
56  * @param pitch_delay_min lower bound (integer) of pitch delay interval
57  * for second subframe
58  *
59  * @return pitch delay in 1/3 units
60  *
61  * Pitch delay is coded:
62  * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
63  *
64  * @remark The routine is used in G.729 @@8k, AMR @@10.2k, AMR @@7.95k,
65  * AMR @@7.4k for the second subframe.
66  */
67 static inline int ff_acelp_decode_5_6_bit_to_2nd_delay3(int ac_index,
68  int pitch_delay_min)
69 {
70  return 3 * pitch_delay_min + ac_index - 2;
71 }
72 
73 /**
74  * @brief Decode pitch delay with 1/3 precision.
75  * @param ac_index adaptive codebook index (4 bits)
76  * @param pitch_delay_min lower bound (integer) of pitch delay interval for
77  * second subframe
78  *
79  * @return pitch delay in 1/3 units
80  *
81  * Pitch delay is coded:
82  * integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2
83  * with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1
84  * integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5
85  *
86  * @remark The routine is used in G.729 @@6.4k, AMR @@6.7k, AMR @@5.9k,
87  * AMR @@5.15k, AMR @@4.75k for the second subframe.
88  */
89 static inline int ff_acelp_decode_4bit_to_2nd_delay3(int ac_index,
90  int pitch_delay_min)
91 {
92  if (ac_index < 4)
93  return 3 * (ac_index + pitch_delay_min);
94  else if (ac_index < 12)
95  return 3 * pitch_delay_min + ac_index + 6;
96  else
97  return 3 * (ac_index + pitch_delay_min) - 18;
98 }
99 
100 /**
101  * @brief Decode pitch delay of the first subframe encoded by 9 bits
102  * with 1/6 precision.
103  * @param ac_index adaptive codebook index (9 bits)
104  *
105  * @return pitch delay in 1/6 units
106  *
107  * Pitch delay is coded:
108  * with 1/6 resolution, 17 < pitch_delay < 95
109  * integers only, 95 <= pitch_delay <= 143
110  *
111  * @remark The routine is used in AMR @@12.2k for the first and third subframes.
112  */
113 static inline int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
114 {
115  if (ac_index < 463)
116  return ac_index + 105;
117  else
118  return 6 * (ac_index - 368);
119 }
120 
121 /**
122  * @brief Decode pitch delay of the second subframe encoded by 6 bits
123  * with 1/6 precision.
124  * @param ac_index adaptive codebook index (6 bits)
125  * @param pitch_delay_min lower bound (integer) of pitch delay interval for
126  * second subframe
127  *
128  * @return pitch delay in 1/6 units
129  *
130  * Pitch delay is coded:
131  * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
132  *
133  * @remark The routine is used in AMR @@12.2k for the second and fourth subframes.
134  */
135 static inline int ff_acelp_decode_6bit_to_2nd_delay6(int ac_index,
136  int pitch_delay_min)
137 {
138  return 6 * pitch_delay_min + ac_index - 3;
139 }
140 
141 /**
142  * @brief Update past quantized energies
143  * @param[in,out] quant_energy past quantized energies (5.10)
144  * @param gain_corr_factor gain correction factor
145  * @param log2_ma_pred_order log2() of MA prediction order
146  * @param erasure frame erasure flag
147  *
148  * If frame erasure flag is not equal to zero, memory is updated with
149  * averaged energy, attenuated by 4dB:
150  * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order
151  *
152  * In normal mode memory is updated with
153  * Er - Ep = 20 * log10(gain_corr_factor)
154  *
155  * @remark The routine is used in G.729 and AMR (all modes).
156  */
158  int16_t* quant_energy,
159  int gain_corr_factor,
160  int log2_ma_pred_order,
161  int erasure);
162 
163 /**
164  * @brief Decode the adaptive codebook gain and add
165  * correction (4.1.5 and 3.9.1 of G.729).
166  * @param adsp initialized audio DSP context
167  * @param gain_corr_factor gain correction factor (2.13)
168  * @param fc_v fixed-codebook vector (2.13)
169  * @param mr_energy mean innovation energy and fixed-point correction (7.13)
170  * @param[in,out] quant_energy past quantized energies (5.10)
171  * @param subframe_size length of subframe
172  *
173  * @return quantized fixed-codebook gain (14.1)
174  *
175  * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
176  *
177  * Em - mean innovation energy (dB, constant, depends on decoding algorithm)
178  * Ep - mean-removed predicted energy (dB)
179  * Er - mean-removed innovation energy (dB)
180  * Ei - mean energy of the fixed-codebook contribution (dB)
181  * N - subframe_size
182  * M - MA (Moving Average) prediction order
183  * gc - fixed-codebook gain
184  * gc_p - predicted fixed-codebook gain
185  *
186  * Fixed codebook gain is computed using predicted gain gc_p and
187  * correction factor gain_corr_factor as shown below:
188  *
189  * gc = gc_p * gain_corr_factor
190  *
191  * The predicted fixed codebook gain gc_p is found by predicting
192  * the energy of the fixed-codebook contribution from the energy
193  * of previous fixed-codebook contributions.
194  *
195  * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
196  *
197  * Ei = 10log(mean)
198  *
199  * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
200  *
201  * Replacing Er with Ep and gc with gc_p we will receive:
202  *
203  * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
204  *
205  * and from above:
206  *
207  * gc_p = 10^((Ep - Ei + Em) / 20)
208  *
209  * Ep is predicted using past energies and prediction coefficients:
210  *
211  * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
212  *
213  * gc_p in fixed-point arithmetic is calculated as following:
214  *
215  * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } =
216  * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26
217  *
218  * Ei = 10log(mean) = -10log(N) - 10log(2^26) +
219  * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
220  *
221  * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -
222  * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) =
223  * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
224  *
225  * gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
226  * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
227  *
228  * where
229  *
230  * mr_energy = Em + 10log(N) + 10log(2^26)
231  *
232  * @remark The routine is used in G.729 and AMR (all modes).
233  */
235  AudioDSPContext *adsp,
236  int gain_corr_factor,
237  const int16_t* fc_v,
238  int mr_energy,
239  const int16_t* quant_energy,
240  const int16_t* ma_prediction_coeff,
241  int subframe_size,
242  int max_pred_order);
243 
244 /**
245  * Calculate fixed gain (part of section 6.1.3 of AMR spec)
246  *
247  * @param fixed_gain_factor gain correction factor
248  * @param fixed_mean_energy mean decoded algebraic codebook vector energy
249  * @param prediction_error vector of the quantified predictor errors of
250  * the four previous subframes. It is updated by this function.
251  * @param energy_mean desired mean innovation energy
252  * @param pred_table table of four moving average coefficients
253  */
254 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
255  float *prediction_error, float energy_mean,
256  const float *pred_table);
257 
258 
259 /**
260  * Decode the adaptive codebook index to the integer and fractional parts
261  * of the pitch lag for one subframe at 1/3 fractional precision.
262  *
263  * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1.
264  *
265  * @param lag_int integer part of pitch lag of the current subframe
266  * @param lag_frac fractional part of pitch lag of the current subframe
267  * @param pitch_index parsed adaptive codebook (pitch) index
268  * @param prev_lag_int integer part of pitch lag for the previous subframe
269  * @param subframe current subframe number
270  * @param third_as_first treat the third frame the same way as the first
271  */
272 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
273  const int prev_lag_int, const int subframe,
274  int third_as_first, int resolution);
275 
276 #endif /* AVCODEC_ACELP_PITCH_DELAY_H */
static int ff_acelp_decode_4bit_to_2nd_delay3(int ac_index, int pitch_delay_min)
Decode pitch delay with 1/3 precision.
static int ff_acelp_decode_8bit_to_1st_delay3(int ac_index)
Decode pitch delay of the first subframe encoded by 8 bits with 1/3 resolution.
float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy, float *prediction_error, float energy_mean, const float *pred_table)
Calculate fixed gain (part of section 6.1.3 of AMR spec)
int16_t ff_acelp_decode_gain_code(AudioDSPContext *adsp, int gain_corr_factor, const int16_t *fc_v, int mr_energy, const int16_t *quant_energy, const int16_t *ma_prediction_coeff, int subframe_size, int max_pred_order)
Decode the adaptive codebook gain and add correction (4.1.5 and 3.9.1 of G.729).
void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index, const int prev_lag_int, const int subframe, int third_as_first, int resolution)
Decode the adaptive codebook index to the integer and fractional parts of the pitch lag for one subfr...
static int ff_acelp_decode_5_6_bit_to_2nd_delay3(int ac_index, int pitch_delay_min)
Decode pitch delay of the second subframe encoded by 5 or 6 bits with 1/3 precision.
static int ff_acelp_decode_9bit_to_1st_delay6(int ac_index)
Decode pitch delay of the first subframe encoded by 9 bits with 1/6 precision.
static int ff_acelp_decode_6bit_to_2nd_delay6(int ac_index, int pitch_delay_min)
Decode pitch delay of the second subframe encoded by 6 bits with 1/6 precision.
void ff_acelp_update_past_gain(int16_t *quant_energy, int gain_corr_factor, int log2_ma_pred_order, int erasure)
Update past quantized energies.
static const float energy_mean[8]
desired mean innovation energy, indexed by active mode
Definition: amrnbdata.h:1453
static const uint16_t ma_prediction_coeff[4]
MA prediction coefficients (3.9.1 of G.729, near Equation 69)
Definition: g729data.h:343