michael@0: /***********************************************************************
michael@0: Copyright (c) 2006-2011, Skype Limited. All rights reserved.
michael@0: Redistribution and use in source and binary forms, with or without
michael@0: modification, are permitted provided that the following conditions
michael@0: are met:
michael@0: - Redistributions of source code must retain the above copyright notice,
michael@0: this list of conditions and the following disclaimer.
michael@0: - Redistributions in binary form must reproduce the above copyright
michael@0: notice, this list of conditions and the following disclaimer in the
michael@0: documentation and/or other materials provided with the distribution.
michael@0: - Neither the name of Internet Society, IETF or IETF Trust, nor the
michael@0: names of specific contributors, may be used to endorse or promote
michael@0: products derived from this software without specific prior written
michael@0: permission.
michael@0: THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
michael@0: AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
michael@0: IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
michael@0: ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
michael@0: LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
michael@0: CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
michael@0: SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
michael@0: INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
michael@0: CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
michael@0: ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
michael@0: POSSIBILITY OF SUCH DAMAGE.
michael@0: ***********************************************************************/
michael@0: 
michael@0: #ifdef HAVE_CONFIG_H
michael@0: #include "config.h"
michael@0: #endif
michael@0: 
michael@0: /*
michael@0:     Elliptic/Cauer filters designed with 0.1 dB passband ripple,
michael@0:     80 dB minimum stopband attenuation, and
michael@0:     [0.95 : 0.15 : 0.35] normalized cut off frequencies.
michael@0: */
michael@0: 
michael@0: #include "main.h"
michael@0: 
michael@0: /* Helper function, interpolates the filter taps */
michael@0: static OPUS_INLINE void silk_LP_interpolate_filter_taps(
michael@0:     opus_int32           B_Q28[ TRANSITION_NB ],
michael@0:     opus_int32           A_Q28[ TRANSITION_NA ],
michael@0:     const opus_int       ind,
michael@0:     const opus_int32     fac_Q16
michael@0: )
michael@0: {
michael@0:     opus_int nb, na;
michael@0: 
michael@0:     if( ind < TRANSITION_INT_NUM - 1 ) {
michael@0:         if( fac_Q16 > 0 ) {
michael@0:             if( fac_Q16 < 32768 ) { /* fac_Q16 is in range of a 16-bit int */
michael@0:                 /* Piece-wise linear interpolation of B and A */
michael@0:                 for( nb = 0; nb < TRANSITION_NB; nb++ ) {
michael@0:                     B_Q28[ nb ] = silk_SMLAWB(
michael@0:                         silk_Transition_LP_B_Q28[ ind     ][ nb ],
michael@0:                         silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
michael@0:                         silk_Transition_LP_B_Q28[ ind     ][ nb ],
michael@0:                         fac_Q16 );
michael@0:                 }
michael@0:                 for( na = 0; na < TRANSITION_NA; na++ ) {
michael@0:                     A_Q28[ na ] = silk_SMLAWB(
michael@0:                         silk_Transition_LP_A_Q28[ ind     ][ na ],
michael@0:                         silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
michael@0:                         silk_Transition_LP_A_Q28[ ind     ][ na ],
michael@0:                         fac_Q16 );
michael@0:                 }
michael@0:             } else { /* ( fac_Q16 - ( 1 << 16 ) ) is in range of a 16-bit int */
michael@0:                 silk_assert( fac_Q16 - ( 1 << 16 ) == silk_SAT16( fac_Q16 - ( 1 << 16 ) ) );
michael@0:                 /* Piece-wise linear interpolation of B and A */
michael@0:                 for( nb = 0; nb < TRANSITION_NB; nb++ ) {
michael@0:                     B_Q28[ nb ] = silk_SMLAWB(
michael@0:                         silk_Transition_LP_B_Q28[ ind + 1 ][ nb ],
michael@0:                         silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] -
michael@0:                         silk_Transition_LP_B_Q28[ ind     ][ nb ],
michael@0:                         fac_Q16 - ( (opus_int32)1 << 16 ) );
michael@0:                 }
michael@0:                 for( na = 0; na < TRANSITION_NA; na++ ) {
michael@0:                     A_Q28[ na ] = silk_SMLAWB(
michael@0:                         silk_Transition_LP_A_Q28[ ind + 1 ][ na ],
michael@0:                         silk_Transition_LP_A_Q28[ ind + 1 ][ na ] -
michael@0:                         silk_Transition_LP_A_Q28[ ind     ][ na ],
michael@0:                         fac_Q16 - ( (opus_int32)1 << 16 ) );
michael@0:                 }
michael@0:             }
michael@0:         } else {
michael@0:             silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ ind ], TRANSITION_NB * sizeof( opus_int32 ) );
michael@0:             silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ ind ], TRANSITION_NA * sizeof( opus_int32 ) );
michael@0:         }
michael@0:     } else {
michael@0:         silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NB * sizeof( opus_int32 ) );
michael@0:         silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NA * sizeof( opus_int32 ) );
michael@0:     }
michael@0: }
michael@0: 
michael@0: /* Low-pass filter with variable cutoff frequency based on  */
michael@0: /* piece-wise linear interpolation between elliptic filters */
michael@0: /* Start by setting psEncC->mode <> 0;                      */
michael@0: /* Deactivate by setting psEncC->mode = 0;                  */
michael@0: void silk_LP_variable_cutoff(
michael@0:     silk_LP_state               *psLP,                          /* I/O  LP filter state                             */
michael@0:     opus_int16                  *frame,                         /* I/O  Low-pass filtered output signal             */
michael@0:     const opus_int              frame_length                    /* I    Frame length                                */
michael@0: )
michael@0: {
michael@0:     opus_int32   B_Q28[ TRANSITION_NB ], A_Q28[ TRANSITION_NA ], fac_Q16 = 0;
michael@0:     opus_int     ind = 0;
michael@0: 
michael@0:     silk_assert( psLP->transition_frame_no >= 0 && psLP->transition_frame_no <= TRANSITION_FRAMES );
michael@0: 
michael@0:     /* Run filter if needed */
michael@0:     if( psLP->mode != 0 ) {
michael@0:         /* Calculate index and interpolation factor for interpolation */
michael@0: #if( TRANSITION_INT_STEPS == 64 )
michael@0:         fac_Q16 = silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 - 6 );
michael@0: #else
michael@0:         fac_Q16 = silk_DIV32_16( silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 ), TRANSITION_FRAMES );
michael@0: #endif
michael@0:         ind      = silk_RSHIFT( fac_Q16, 16 );
michael@0:         fac_Q16 -= silk_LSHIFT( ind, 16 );
michael@0: 
michael@0:         silk_assert( ind >= 0 );
michael@0:         silk_assert( ind < TRANSITION_INT_NUM );
michael@0: 
michael@0:         /* Interpolate filter coefficients */
michael@0:         silk_LP_interpolate_filter_taps( B_Q28, A_Q28, ind, fac_Q16 );
michael@0: 
michael@0:         /* Update transition frame number for next frame */
michael@0:         psLP->transition_frame_no = silk_LIMIT( psLP->transition_frame_no + psLP->mode, 0, TRANSITION_FRAMES );
michael@0: 
michael@0:         /* ARMA low-pass filtering */
michael@0:         silk_assert( TRANSITION_NB == 3 && TRANSITION_NA == 2 );
michael@0:         silk_biquad_alt( frame, B_Q28, A_Q28, psLP->In_LP_State, frame, frame_length, 1);
michael@0:     }
michael@0: }