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 */
43int 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 */
60int 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 */
80int 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 */
99int 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 */
115int 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 */
135void 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 */
213int16_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 */
233float 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 */
251void 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 */
256