1 /*********************************************************************** 2 Copyright (c) 2006-2011, Skype Limited. All rights reserved. 3 Redistribution and use in source and binary forms, with or without 4 modification, are permitted provided that the following conditions 5 are met: 6 - Redistributions of source code must retain the above copyright notice, 7 this list of conditions and the following disclaimer. 8 - Redistributions in binary form must reproduce the above copyright 9 notice, this list of conditions and the following disclaimer in the 10 documentation and/or other materials provided with the distribution. 11 - Neither the name of Internet Society, IETF or IETF Trust, nor the 12 names of specific contributors, may be used to endorse or promote 13 products derived from this software without specific prior written 14 permission. 15 THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" 16 AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 17 IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 18 ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE 19 LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 20 CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 21 SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 22 INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 23 CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 24 ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 25 POSSIBILITY OF SUCH DAMAGE. 26 ***********************************************************************/ 27 28 #ifdef HAVE_CONFIG_H 29 #include "config.h" 30 #endif 31 32 /* 33 Elliptic/Cauer filters designed with 0.1 dB passband ripple, 34 80 dB minimum stopband attenuation, and 35 [0.95 : 0.15 : 0.35] normalized cut off frequencies. 36 */ 37 38 #include "main.h" 39 40 /* Helper function, interpolates the filter taps */ 41 static OPUS_INLINE void silk_LP_interpolate_filter_taps( 42 opus_int32 B_Q28[ TRANSITION_NB ], 43 opus_int32 A_Q28[ TRANSITION_NA ], 44 const opus_int ind, 45 const opus_int32 fac_Q16 46 ) 47 { 48 opus_int nb, na; 49 50 if( ind < TRANSITION_INT_NUM - 1 ) { 51 if( fac_Q16 > 0 ) { 52 if( fac_Q16 < 32768 ) { /* fac_Q16 is in range of a 16-bit int */ 53 /* Piece-wise linear interpolation of B and A */ 54 for( nb = 0; nb < TRANSITION_NB; nb++ ) { 55 B_Q28[ nb ] = silk_SMLAWB( 56 silk_Transition_LP_B_Q28[ ind ][ nb ], 57 silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] - 58 silk_Transition_LP_B_Q28[ ind ][ nb ], 59 fac_Q16 ); 60 } 61 for( na = 0; na < TRANSITION_NA; na++ ) { 62 A_Q28[ na ] = silk_SMLAWB( 63 silk_Transition_LP_A_Q28[ ind ][ na ], 64 silk_Transition_LP_A_Q28[ ind + 1 ][ na ] - 65 silk_Transition_LP_A_Q28[ ind ][ na ], 66 fac_Q16 ); 67 } 68 } else { /* ( fac_Q16 - ( 1 << 16 ) ) is in range of a 16-bit int */ 69 silk_assert( fac_Q16 - ( 1 << 16 ) == silk_SAT16( fac_Q16 - ( 1 << 16 ) ) ); 70 /* Piece-wise linear interpolation of B and A */ 71 for( nb = 0; nb < TRANSITION_NB; nb++ ) { 72 B_Q28[ nb ] = silk_SMLAWB( 73 silk_Transition_LP_B_Q28[ ind + 1 ][ nb ], 74 silk_Transition_LP_B_Q28[ ind + 1 ][ nb ] - 75 silk_Transition_LP_B_Q28[ ind ][ nb ], 76 fac_Q16 - ( (opus_int32)1 << 16 ) ); 77 } 78 for( na = 0; na < TRANSITION_NA; na++ ) { 79 A_Q28[ na ] = silk_SMLAWB( 80 silk_Transition_LP_A_Q28[ ind + 1 ][ na ], 81 silk_Transition_LP_A_Q28[ ind + 1 ][ na ] - 82 silk_Transition_LP_A_Q28[ ind ][ na ], 83 fac_Q16 - ( (opus_int32)1 << 16 ) ); 84 } 85 } 86 } else { 87 silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ ind ], TRANSITION_NB * sizeof( opus_int32 ) ); 88 silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ ind ], TRANSITION_NA * sizeof( opus_int32 ) ); 89 } 90 } else { 91 silk_memcpy( B_Q28, silk_Transition_LP_B_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NB * sizeof( opus_int32 ) ); 92 silk_memcpy( A_Q28, silk_Transition_LP_A_Q28[ TRANSITION_INT_NUM - 1 ], TRANSITION_NA * sizeof( opus_int32 ) ); 93 } 94 } 95 96 /* Low-pass filter with variable cutoff frequency based on */ 97 /* piece-wise linear interpolation between elliptic filters */ 98 /* Start by setting psEncC->mode <> 0; */ 99 /* Deactivate by setting psEncC->mode = 0; */ 100 void silk_LP_variable_cutoff( 101 silk_LP_state *psLP, /* I/O LP filter state */ 102 opus_int16 *frame, /* I/O Low-pass filtered output signal */ 103 const opus_int frame_length /* I Frame length */ 104 ) 105 { 106 opus_int32 B_Q28[ TRANSITION_NB ], A_Q28[ TRANSITION_NA ], fac_Q16 = 0; 107 opus_int ind = 0; 108 109 silk_assert( psLP->transition_frame_no >= 0 && psLP->transition_frame_no <= TRANSITION_FRAMES ); 110 111 /* Run filter if needed */ 112 if( psLP->mode != 0 ) { 113 /* Calculate index and interpolation factor for interpolation */ 114 #if( TRANSITION_INT_STEPS == 64 ) 115 fac_Q16 = silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 - 6 ); 116 #else 117 fac_Q16 = silk_DIV32_16( silk_LSHIFT( TRANSITION_FRAMES - psLP->transition_frame_no, 16 ), TRANSITION_FRAMES ); 118 #endif 119 ind = silk_RSHIFT( fac_Q16, 16 ); 120 fac_Q16 -= silk_LSHIFT( ind, 16 ); 121 122 silk_assert( ind >= 0 ); 123 silk_assert( ind < TRANSITION_INT_NUM ); 124 125 /* Interpolate filter coefficients */ 126 silk_LP_interpolate_filter_taps( B_Q28, A_Q28, ind, fac_Q16 ); 127 128 /* Update transition frame number for next frame */ 129 psLP->transition_frame_no = silk_LIMIT( psLP->transition_frame_no + psLP->mode, 0, TRANSITION_FRAMES ); 130 131 /* ARMA low-pass filtering */ 132 silk_assert( TRANSITION_NB == 3 && TRANSITION_NA == 2 ); 133 silk_biquad_alt( frame, B_Q28, A_Q28, psLP->In_LP_State, frame, frame_length, 1); 134 } 135 } 136
