acelp_pitch_delay.h File Reference

#include <stdint.h>

Go to the source code of this file.

Defines

#define PITCH_DELAY_MIN   20
#define PITCH_DELAY_MAX   143

Functions

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.
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.
int ff_acelp_decode_4bit_to_2nd_delay3 (int ac_index, int pitch_delay_min)
 Decode pitch delay with 1/3 precision.
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.
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.
int16_t ff_acelp_decode_gain_code (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).

Define Documentation

#define PITCH_DELAY_MAX   143

Definition at line 29 of file acelp_pitch_delay.h.

#define PITCH_DELAY_MIN   20

Definition at line 28 of file acelp_pitch_delay.h.

Function Documentation

int ff_acelp_decode_4bit_to_2nd_delay3 ( int  ac_index,
int  pitch_delay_min 
)

Decode pitch delay with 1/3 precision.

Parameters:
ac_index adaptive codebook index (4 bits)
pitch_delay_min lower bound (integer) of pitch delay interval for second subframe
Returns:
pitch delay in 1/3 units
Pitch delay is coded: integers only, -6 < pitch_delay - int(prev_pitch_delay) <= -2 with 1/3 resolution, -2 < pitch_delay - int(prev_pitch_delay) < 1 integers only, 1 <= pitch_delay - int(prev_pitch_delay) < 5

Remarks:
The routine is used in G.729 .4k, AMR .7k, AMR .9k, AMR .15k, AMR .75k for the second subframe.

Definition at line 35 of file acelp_pitch_delay.c.

00038 {
00039     if(ac_index < 4)
00040         return 3 * (ac_index + pitch_delay_min);
00041     else if(ac_index < 12)
00042         return 3 * pitch_delay_min + ac_index + 6;
00043     else
00044         return 3 * (ac_index + pitch_delay_min) - 18;
00045 }

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.

Parameters:
ac_index adaptive codebook index (5 or 6 bits)
pitch_delay_min lower bound (integer) of pitch delay interval for second subframe
Returns:
pitch delay in 1/3 units
Pitch delay is coded: with 1/3 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5

Remarks:
The routine is used in G.729 , AMR .2k, AMR .95k, AMR .4k for the second subframe.

Definition at line 47 of file acelp_pitch_delay.c.

00050 {
00051         return 3 * pitch_delay_min + ac_index - 2;
00052 }

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.

Parameters:
ac_index adaptive codebook index (6 bits)
pitch_delay_min lower bound (integer) of pitch delay interval for second subframe
Returns:
pitch delay in 1/6 units
Pitch delay is coded: with 1/6 resolution, -6 < pitch_delay - int(prev_pitch_delay) < 5

Remarks:
The routine is used in AMR .2k for the second and fourth subframes.

Definition at line 61 of file acelp_pitch_delay.c.

00064 {
00065     return 6 * pitch_delay_min + ac_index - 3;
00066 }

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.

Parameters:
ac_index adaptive codebook index (8 bits)
Returns:
pitch delay in 1/3 units
Pitch delay is coded: with 1/3 resolution, 19 < pitch_delay < 85 integers only, 85 <= pitch_delay <= 143

Definition at line 27 of file acelp_pitch_delay.c.

00028 {
00029     ac_index += 58;
00030     if(ac_index > 254)
00031         ac_index = 3 * ac_index - 510;
00032     return ac_index;
00033 }

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.

Parameters:
ac_index adaptive codebook index (9 bits)
pitch_delay_min lower bound (integer) of pitch delay interval for second subframe
Returns:
pitch delay in 1/6 units
Pitch delay is coded: with 1/6 resolution, 17 < pitch_delay < 95 integers only, 95 <= pitch_delay <= 143

Remarks:
The routine is used in AMR .2k for the first and third subframes.

Definition at line 54 of file acelp_pitch_delay.c.

00055 {
00056     if(ac_index < 463)
00057         return ac_index + 105;
00058     else
00059         return 6 * (ac_index - 368);
00060 }

int16_t ff_acelp_decode_gain_code ( 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).

Parameters:
gain_corr_factor gain correction factor (2.13)
fc_v fixed-codebook vector (2.13)
mr_energy mean innovation energy and fixed-point correction (7.13)
quant_energy [in/out] past quantized energies (5.10)
subframe_size length of subframe
ma_pred_order MA prediction order
Returns:
quantized fixed-codebook gain (14.1)
The routine implements equations 69, 66 and 71 of the G.729 specification (3.9.1)

Em - mean innovation energy (dB, constant, depends on decoding algorithm) Ep - mean-removed predicted energy (dB) Er - mean-removed innovation energy (dB) Ei - mean energy of the fixed-codebook contribution (dB) N - subframe_size M - MA (Moving Average) prediction order gc - fixed-codebook gain gc_p - predicted fixed-codebook gain

Fixed codebook gain is computed using predicted gain gc_p and correction factor gain_corr_factor as shown below:

gc = gc_p * gain_corr_factor

The predicted fixed codebook gain gc_p is found by predicting the energy of the fixed-codebook contribution from the energy of previous fixed-codebook contributions.

mean = 1/N * sum(i,0,N){ fc_v[i] * fc_v[i] }

Ei = 10log(mean)

Er = 10log(1/N * gc^2 * mean) - Em = 20log(gc) + Ei - Em

Replacing Er with Ep and gc with gc_p we will receive:

Ep = 10log(1/N * gc_p^2 * mean) - Em = 20log(gc_p) + Ei - Em

and from above:

gc_p = 10^((Ep - Ei + Em) / 20)

Ep is predicted using past energies and prediction coefficients:

Ep = sum(i,0,M){ ma_prediction_coeff[i] * quant_energy[i] }

gc_p in fixed-point arithmetic is calculated as following:

mean = 1/N * sum(i,0,N){ (fc_v[i] / 2^13) * (fc_v[i] / 2^13) } = = 1/N * sum(i,0,N) { fc_v[i] * fc_v[i] } / 2^26

Ei = 10log(mean) = -10log(N) - 10log(2^26) + + 10log(sum(i,0,N) { fc_v[i] * fc_v[i] })

Ep - Ei + Em = Ep + Em + 10log(N) + 10log(2^26) -

gc_p = 10 ^ ((Ep - Ei + Em) / 20) = = 2 ^ (3.3219 * (Ep - Ei + Em) / 20) = 2 ^ (0.166 * (Ep - Ei + Em))

where

mr_energy = Em + 10log(N) + 10log(2^26)

Remarks:
The routine is used in G.729 and AMR (all modes).

Definition at line 89 of file acelp_pitch_delay.c.

References bidir_sal(), dot_product(), ff_exp2(), and ff_log2().

00097 {
00098     int i;
00099 
00100     mr_energy <<= 10;
00101 
00102     for(i=0; i<ma_pred_order; i++)
00103         mr_energy += quant_energy[i] * ma_prediction_coeff[i];
00104 
00105 #ifdef G729_BITEXACT
00106     mr_energy += (((-6165LL * ff_log2(dot_product(fc_v, fc_v, subframe_size, 0))) >> 3) & ~0x3ff);
00107 
00108     mr_energy = (5439 * (mr_energy >> 15)) >> 8;           // (0.15) = (0.15) * (7.23)
00109 
00110     return bidir_sal(
00111                ((ff_exp2(mr_energy & 0x7fff) + 16) >> 5) * (gain_corr_factor >> 1),
00112                (mr_energy >> 15) - 25
00113            );
00114 #else
00115     mr_energy = gain_corr_factor * exp(M_LN10 / (20 << 23) * mr_energy) /
00116                 sqrt(dot_product(fc_v, fc_v, subframe_size, 0));
00117     return mr_energy >> 12;
00118 #endif
00119 }

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.

Parameters:
quant_energy [in/out] past quantized energies (5.10)
gain_corr_factor gain correction factor
log2_ma_pred_order log2() of MA prediction order
erasure frame erasure flag
If frame erasure flag is not equal to zero, memory is updated with averaged energy, attenuated by 4dB: max(avg(quant_energy[i])-4, -14), i=0,ma_pred_order

In normal mode memory is updated with Er - Ep = 20 * log10(gain_corr_factor)

Remarks:
The routine is used in G.729 and AMR (all modes).

Definition at line 68 of file acelp_pitch_delay.c.

References ff_log2(), and FFMAX.

00073 {
00074     int i;
00075     int avg_gain=quant_energy[(1 << log2_ma_pred_order) - 1]; // (5.10)
00076 
00077     for(i=(1 << log2_ma_pred_order) - 1; i>0; i--)
00078     {
00079         avg_gain       += quant_energy[i-1];
00080         quant_energy[i] = quant_energy[i-1];
00081     }
00082 
00083     if(erasure)
00084         quant_energy[0] = FFMAX(avg_gain >> log2_ma_pred_order, -10240) - 4096; // -10 and -4 in (5.10)
00085     else
00086         quant_energy[0] = (6165 * ((ff_log2(gain_corr_factor) >> 2) - (13 << 13))) >> 13;
00087 }

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