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/***********************************************************************
Copyright (c) 2006-2011, Skype Limited. All rights reserved.
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modification, are permitted provided that the following conditions
are met:
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names of specific contributors, may be used to endorse or promote
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THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
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***********************************************************************/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
/*
Elliptic/Cauer filters designed with 0.1 dB passband ripple,
80 dB minimum stopband attenuation, and
[0.95 : 0.15 : 0.35] normalized cut off frequencies.
*/
#include "main.h"
/* Helper function, interpolates the filter taps */
static OPUS_INLINE void silk_LP_interpolate_filter_taps(
opus_int32 B_Q28[ TRANSITION_NB ],
opus_int32 A_Q28[ TRANSITION_NA ],
const opus_int ind,
const opus_int32 fac_Q16
)
{
opus_int nb, na;
if( ind < TRANSITION_INT_NUM - 1 ) {
if( fac_Q16 > 0 ) {
if( fac_Q16 < 32768 ) { /* fac_Q16 is in range of a 16-bit int */
/* Piece-wise linear interpolation of B and A */
for( nb = 0; nb < TRANSITION_NB; nb++ ) {
B_Q28[ nb ] = silk_SMLAWB(
silk_Transition_LP_B_Q28[ ind ][ nb ],
silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
silk_Transition_LP_B_Q28[ ind ][ nb ],
fac_Q16 );
}
for( na = 0; na < TRANSITION_NA; na++ ) {
A_Q28[ na ] = silk_SMLAWB(
silk_Transition_LP_A_Q28[ ind ][ na ],
silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
silk_Transition_LP_A_Q28[ ind ][ na ],
fac_Q16 );
}
} else { /* ( fac_Q16 - ( 1 << 16 ) ) is in range of a 16-bit int */
silk_assert( fac_Q16 - ( 1 << 16 ) == silk_SAT16( fac_Q16 - ( 1 << 16 ) ) );
/* Piece-wise linear interpolation of B and A */
for( nb = 0; nb < TRANSITION_NB; nb++ ) {
B_Q28[ nb ] = silk_SMLAWB(
silk_Transition_LP_B_Q28[ ind + 1 ][ nb ],
silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
silk_Transition_LP_B_Q28[ ind ][ nb ],
fac_Q16 - ( (opus_int32)1 << 16 ) );
}
for( na = 0; na < TRANSITION_NA; na++ ) {
A_Q28[ na ] = silk_SMLAWB(
silk_Transition_LP_A_Q28[ ind + 1 ][ na ],
silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
silk_Transition_LP_A_Q28[ ind ][ na ],
fac_Q16 - ( (opus_int32)1 << 16 ) );
}
}
} else {
silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ ind ], TRANSITION_NB * sizeof( opus_int32 ) );
silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ ind ], TRANSITION_NA * sizeof( opus_int32 ) );
}
} else {
silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NB * sizeof( opus_int32 ) );
silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NA * sizeof( opus_int32 ) );
}
}
/* Low-pass filter with variable cutoff frequency based on */
/* piece-wise linear interpolation between elliptic filters */
/* Start by setting psEncC->mode <> 0; */
/* Deactivate by setting psEncC->mode = 0; */
void silk_LP_variable_cutoff(
silk_LP_state *psLP, /* I/O LP filter state */
opus_int16 *frame, /* I/O Low-pass filtered output signal */
const opus_int frame_length /* I Frame length */
)
{
opus_int32 B_Q28[ TRANSITION_NB ], A_Q28[ TRANSITION_NA ], fac_Q16 = 0;
opus_int ind = 0;
silk_assert( psLP->transition_frame_no >= 0 && psLP->transition_frame_no <= TRANSITION_FRAMES );
/* Run filter if needed */
if( psLP->mode != 0 ) {
/* Calculate index and interpolation factor for interpolation */
#if( TRANSITION_INT_STEPS == 64 )
fac_Q16 = silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 - 6 );
#else
fac_Q16 = silk_DIV32_16( silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 ), TRANSITION_FRAMES );
#endif
ind = silk_RSHIFT( fac_Q16, 16 );
fac_Q16 -= silk_LSHIFT( ind, 16 );
silk_assert( ind >= 0 );
silk_assert( ind < TRANSITION_INT_NUM );
/* Interpolate filter coefficients */
silk_LP_interpolate_filter_taps( B_Q28, A_Q28, ind, fac_Q16 );
/* Update transition frame number for next frame */
psLP->transition_frame_no = silk_LIMIT( psLP->transition_frame_no + psLP->mode, 0, TRANSITION_FRAMES );
/* ARMA low-pass filtering */
silk_assert( TRANSITION_NB == 3 && TRANSITION_NA == 2 );
silk_biquad_alt_stride1( frame, B_Q28, A_Q28, psLP->In_LP_State, frame, frame_length);
}
}