d833dba2b80172464b565a155989407b6f022a1e
[libav.git] / libavcodec / acelp_pitch_delay.h
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 */
60 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
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 */
80 int ff_acelp_decode_4bit_to_2nd_delay3(
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 * \param pitch_delay_min lower bound (integer) of pitch delay interval for
89 * second subframe
90 *
91 * \return pitch delay in 1/6 units
92 *
93 * Pitch delay is coded:
94 * with 1/6 resolution, 17 < pitch_delay < 95
95 * integers only, 95 <= pitch_delay <= 143
96 *
97 * \remark The routine is used in AMR @12.2k for the first and third subframes.
98 */
99 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index);
100
101 /**
102 * \brief Decode pitch delay of the second subframe encoded by 6 bits
103 * with 1/6 precision.
104 * \param ac_index adaptive codebook index (6 bits)
105 * \param pitch_delay_min lower bound (integer) of pitch delay interval for
106 * second subframe
107 *
108 * \return pitch delay in 1/6 units
109 *
110 * Pitch delay is coded:
111 * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
112 *
113 * \remark The routine is used in AMR @12.2k for the second and fourth subframes.
114 */
115 int ff_acelp_decode_6bit_to_2nd_delay6(
116 int ac_index,
117 int pitch_delay_min);
118
119 /**
120 * \brief Update past quantized energies
121 * \param quant_energy [in/out] past quantized energies (5.10)
122 * \param gain_corr_factor gain correction factor
123 * \param log2_ma_pred_order log2() of MA prediction order
124 * \param erasure frame erasure flag
125 *
126 * If frame erasure flag is not equal to zero, memory is updated with
127 * averaged energy, attenuated by 4dB:
128 * max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order
129 *
130 * In normal mode memory is updated with
131 * Er - Ep = 20 * log10(gain_corr_factor)
132 *
133 * \remark The routine is used in G.729 and AMR (all modes).
134 */
135 void ff_acelp_update_past_gain(
136 int16_t* quant_energy,
137 int gain_corr_factor,
138 int log2_ma_pred_order,
139 int erasure);
140
141 /**
142 * \brief Decode the adaptive codebook gain and add
143 * correction (4.1.5 and 3.9.1 of G.729).
144 * \param dsp initialized dsputil context
145 * \param gain_corr_factor gain correction factor (2.13)
146 * \param fc_v fixed-codebook vector (2.13)
147 * \param mr_energy mean innovation energy and fixed-point correction (7.13)
148 * \param quant_energy [in/out] past quantized energies (5.10)
149 * \param subframe_size length of subframe
150 * \param ma_pred_order MA prediction order
151 *
152 * \return quantized fixed-codebook gain (14.1)
153 *
154 * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
155 *
156 * Em - mean innovation energy (dB, constant, depends on decoding algorithm)
157 * Ep - mean-removed predicted energy (dB)
158 * Er - mean-removed innovation energy (dB)
159 * Ei - mean energy of the fixed-codebook contribution (dB)
160 * N - subframe_size
161 * M - MA (Moving Average) prediction order
162 * gc - fixed-codebook gain
163 * gc_p - predicted fixed-codebook gain
164 *
165 * Fixed codebook gain is computed using predicted gain gc_p and
166 * correction factor gain_corr_factor as shown below:
167 *
168 * gc = gc_p * gain_corr_factor
169 *
170 * The predicted fixed codebook gain gc_p is found by predicting
171 * the energy of the fixed-codebook contribution from the energy
172 * of previous fixed-codebook contributions.
173 *
174 * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
175 *
176 * Ei = 10log(mean)
177 *
178 * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
179 *
180 * Replacing Er with Ep and gc with gc_p we will receive:
181 *
182 * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
183 *
184 * and from above:
185 *
186 * gc_p = 10^((Ep - Ei + Em) / 20)
187 *
188 * Ep is predicted using past energies and prediction coefficients:
189 *
190 * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
191 *
192 * gc_p in fixed-point arithmetic is calculated as following:
193 *
194 * mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } =
195 * = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26
196 *
197 * Ei = 10log(mean) = -10log(N) - 10log(2^26) +
198 * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
199 *
200 * Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -
201 * - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] }) =
202 * = Ep + mr_energy - 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
203 *
204 * gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
205 * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
206 *
207 * where
208 *
209 * mr_energy = Em + 10log(N) + 10log(2^26)
210 *
211 * \remark The routine is used in G.729 and AMR (all modes).
212 */
213 int16_t ff_acelp_decode_gain_code(
214 DSPContext *dsp,
215 int gain_corr_factor,
216 const int16_t* fc_v,
217 int mr_energy,
218 const int16_t* quant_energy,
219 const int16_t* ma_prediction_coeff,
220 int subframe_size,
221 int max_pred_order);
222
223 /**
224 * Calculate fixed gain (part of section 6.1.3 of AMR spec)
225 *
226 * @param fixed_gain_factor gain correction factor
227 * @param fixed_energy decoded algebraic codebook vector energy
228 * @param prediction_error vector of the quantified predictor errors of
229 * the four previous subframes. It is updated by this function.
230 * @param energy_mean desired mean innovation energy
231 * @param pred_table table of four moving average coefficients
232 */
233 float ff_amr_set_fixed_gain(float fixed_gain_factor, float fixed_mean_energy,
234 float *prediction_error, float energy_mean,
235 const float *pred_table);
236
237
238 /**
239 * Decode the adaptive codebook index to the integer and fractional parts
240 * of the pitch lag for one subframe at 1/3 fractional precision.
241 *
242 * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1.
243 *
244 * @param lag_int integer part of pitch lag of the current subframe
245 * @param lag_frac fractional part of pitch lag of the current subframe
246 * @param pitch_index parsed adaptive codebook (pitch) index
247 * @param prev_lag_int integer part of pitch lag for the previous subframe
248 * @param subframe current subframe number
249 * @param third_as_first treat the third frame the same way as the first
250 */
251 void ff_decode_pitch_lag(int *lag_int, int *lag_frac, int pitch_index,
252 const int prev_lag_int, const int subframe,
253 int third_as_first, int resolution);
254
255 #endif /* AVCODEC_ACELP_PITCH_DELAY_H */