2 * gain code, gain pitch and pitch delay decoding
4 * Copyright (c) 2008 Vladimir Voroshilov
6 * This file is part of FFmpeg.
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23 #ifndef AVCODEC_ACELP_PITCH_DELAY_H
24 #define AVCODEC_ACELP_PITCH_DELAY_H
29 #define PITCH_DELAY_MIN 20
30 #define PITCH_DELAY_MAX 143
33 * \brief Decode pitch delay of the first subframe encoded by 8 bits with 1/3
35 * \param ac_index adaptive codebook index (8 bits)
37 * \return pitch delay in 1/3 units
39 * Pitch delay is coded:
40 * with 1/3 resolution, 19 < pitch_delay < 85
41 * integers only, 85 <= pitch_delay <= 143
43 int ff_acelp_decode_8bit_to_1st_delay3(int ac_index
);
46 * \brief Decode pitch delay of the second subframe encoded by 5 or 6 bits
48 * \param ac_index adaptive codebook index (5 or 6 bits)
49 * \param pitch_delay_min lower bound (integer) of pitch delay interval
52 * \return pitch delay in 1/3 units
54 * Pitch delay is coded:
55 * with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
57 * \remark The routine is used in G.729 @8k, AMR @10.2k, AMR @7.95k,
58 * AMR @7.4k for the second subframe.
60 int ff_acelp_decode_5_6_bit_to_2nd_delay3(
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
70 * \return pitch delay in 1/3 units
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
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.
80 int ff_acelp_decode_4bit_to_2nd_delay3(
85 * \brief Decode pitch delay of the first subframe encoded by 9 bits
87 * \param ac_index adaptive codebook index (9 bits)
88 * \param pitch_delay_min lower bound (integer) of pitch delay interval for
91 * \return pitch delay in 1/6 units
93 * Pitch delay is coded:
94 * with 1/6 resolution, 17 < pitch_delay < 95
95 * integers only, 95 <= pitch_delay <= 143
97 * \remark The routine is used in AMR @12.2k for the first and third subframes.
99 int ff_acelp_decode_9bit_to_1st_delay6(int ac_index
);
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
108 * \return pitch delay in 1/6 units
110 * Pitch delay is coded:
111 * with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5
113 * \remark The routine is used in AMR @12.2k for the second and fourth subframes.
115 int ff_acelp_decode_6bit_to_2nd_delay6(
117 int pitch_delay_min
);
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
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
130 * In normal mode memory is updated with
131 * Er - Ep = 20 * log10(gain_corr_factor)
133 * \remark The routine is used in G.729 and AMR (all modes).
135 void ff_acelp_update_past_gain(
136 int16_t* quant_energy
,
137 int gain_corr_factor
,
138 int log2_ma_pred_order
,
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
152 * \return quantized fixed-codebook gain (14.1)
154 * The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)
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)
161 * M - MA (Moving Average) prediction order
162 * gc - fixed-codebook gain
163 * gc_p - predicted fixed-codebook gain
165 * Fixed codebook gain is computed using predicted gain gc_p and
166 * correction factor gain_corr_factor as shown below:
168 * gc = gc_p * gain_corr_factor
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.
174 * mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }
178 * Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em
180 * Replacing Er with Ep and gc with gc_p we will receive:
182 * Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em
186 * gc_p = 10^((Ep - Ei + Em) / 20)
188 * Ep is predicted using past energies and prediction coefficients:
190 * Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }
192 * gc_p in fixed-point arithmetic is calculated as following:
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
197 * Ei = 10log(mean) = -10log(N) - 10log(2^26) +
198 * + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })
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] })
204 * gc_p = 10 ^ ((Ep - Ei + Em) / 20) =
205 * = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))
209 * mr_energy = Em + 10log(N) + 10log(2^26)
211 * \remark The routine is used in G.729 and AMR (all modes).
213 int16_t ff_acelp_decode_gain_code(
215 int gain_corr_factor
,
218 const int16_t* quant_energy
,
219 const int16_t* ma_prediction_coeff
,
224 * Calculate fixed gain (part of section 6.1.3 of AMR spec)
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
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
);
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.
242 * The choice of pitch lag is described in 3GPP TS 26.090 section 5.6.1.
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
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
);
255 #endif /* AVCODEC_ACELP_PITCH_DELAY_H */