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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);

    }

}