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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: |
| - Redistributions of source code must retain the above copyright notice, |
| this list of conditions and the following disclaimer. |
| - Redistributions in binary form must reproduce the above copyright |
| notice, this list of conditions and the following disclaimer in the |
| documentation and/or other materials provided with the distribution. |
| - Neither the name of Internet Society, IETF or IETF Trust, nor the |
| names of specific contributors, may be used to endorse or promote |
| products derived from this software without specific prior written |
| permission. |
| 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 |
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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); |
| } |
| } |
