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