SKP_int SKP_Silk_init_encoder_FLP(
SKP_Silk_encoder_state_FLP *psEnc /* I/O Encoder state FLP */
) {
SKP_int ret = 0;
/* Clear the entire encoder state */
SKP_memset( psEnc, 0, sizeof( SKP_Silk_encoder_state_FLP ) );
#if HIGH_PASS_INPUT
psEnc->variable_HP_smth1 = SKP_Silk_log2( 70.0 );
psEnc->variable_HP_smth2 = SKP_Silk_log2( 70.0 );
#endif
/* Used to deactivate e.g. LSF interpolation and fluctuation reduction */
psEnc->sCmn.first_frame_after_reset = 1;
/* Initialize Silk VAD */
ret += SKP_Silk_VAD_Init( &psEnc->sCmn.sVAD );
/* Initialize NSQ */
psEnc->sCmn.sNSQ.prev_inv_gain_Q16 = 65536;
psEnc->sCmn.sNSQ_LBRR.prev_inv_gain_Q16 = 65536;
return( ret );
}
/* High-pass filter with cutoff frequency adaptation based on pitch lag statistics */
void SKP_Silk_HP_variable_cutoff_FLP(
SKP_Silk_encoder_state_FLP *psEnc, /* I/O Encoder state FLP */
SKP_Silk_encoder_control_FLP *psEncCtrl, /* I/O Encoder control FLP */
SKP_int16 *out, /* O High-pass filtered output signal */
const SKP_int16 *in /* I Input signal */
)
{
SKP_float pitch_freq_Hz, pitch_freq_log, quality, delta_freq, smth_coef, Fc, r;
SKP_int32 B_Q28[ 3 ], A_Q28[ 2 ];
/*********************************************/
/* Estimate low end of pitch frequency range */
/*********************************************/
if( psEnc->sCmn.prev_sigtype == SIG_TYPE_VOICED ) {
/* Difference, in log domain */
pitch_freq_Hz = 1e3f * psEnc->sCmn.fs_kHz / psEnc->sCmn.prevLag;
pitch_freq_log = SKP_Silk_log2( pitch_freq_Hz );
/* Adjustment based on quality */
quality = psEncCtrl->input_quality_bands[ 0 ];
pitch_freq_log -= quality * quality * ( pitch_freq_log - SKP_Silk_log2( VARIABLE_HP_MIN_FREQ ) );
pitch_freq_log += 0.5f * ( 0.6f - quality );
delta_freq = pitch_freq_log - psEnc->variable_HP_smth1;
if( delta_freq < 0.0 ) {
/* Less smoothing for decreasing pitch frequency, to track something close to the minimum */
delta_freq *= 3.0f;
}
/* Limit delta, to reduce impact of outliers */
delta_freq = SKP_LIMIT_float( delta_freq, -VARIABLE_HP_MAX_DELTA_FREQ, VARIABLE_HP_MAX_DELTA_FREQ );
/* Update smoother */
smth_coef = VARIABLE_HP_SMTH_COEF1 * psEnc->speech_activity;
psEnc->variable_HP_smth1 += smth_coef * delta_freq;
}
/* Second smoother */
psEnc->variable_HP_smth2 += VARIABLE_HP_SMTH_COEF2 * ( psEnc->variable_HP_smth1 - psEnc->variable_HP_smth2 );
/* Convert from log scale to Hertz */
psEncCtrl->pitch_freq_low_Hz = ( SKP_float )pow( 2.0f, psEnc->variable_HP_smth2 );
/* Limit frequency range */
psEncCtrl->pitch_freq_low_Hz = SKP_LIMIT_float( psEncCtrl->pitch_freq_low_Hz, VARIABLE_HP_MIN_FREQ, VARIABLE_HP_MAX_FREQ );
/*******************************/
/* Compute filter coefficients */
/*******************************/
/* Compute cut-off frequency, in radians */
Fc = ( SKP_float )( 0.45f * 2.0f * 3.14159265359 * psEncCtrl->pitch_freq_low_Hz / ( 1e3f * psEnc->sCmn.fs_kHz ) );
/* 2nd order ARMA coefficients */
r = 1.0f - 0.92f * Fc;
/* b = r * [1; -2; 1]; */
/* a = [1; -2 * r * (1 - 0.5 * Fc^2); r^2]; */
B_Q28[ 0 ] = SKP_float2int( ( 1 << 28 ) * r );
B_Q28[ 1 ] = SKP_float2int( ( 1 << 28 ) * -2.0f * r );
B_Q28[ 2 ] = B_Q28[ 0 ];
A_Q28[ 0 ] = SKP_float2int( ( 1 << 28 ) * -2.0f * r * ( 1.0f - 0.5f * Fc * Fc ) );
A_Q28[ 1 ] = SKP_float2int( ( 1 << 28 ) * r * r );
/********************/
/* High-pass filter */
/********************/
SKP_Silk_biquad_alt( in, B_Q28, A_Q28, psEnc->sCmn.In_HP_State, out, psEnc->sCmn.frame_length );
}