FFmpeg coverage


Directory: ../../../ffmpeg/
File: src/libavcodec/acelp_pitch_delay.h
Date: 2021-09-24 20:55:06
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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 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 */
157 void ff_acelp_update_past_gain(
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 */
234 int16_t ff_acelp_decode_gain_code(
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 */
277