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79 lines
4.2 KiB
C
79 lines
4.2 KiB
C
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/***********************************************************************
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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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/* *
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* silk_biquad_alt.c *
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* *
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* Second order ARMA filter *
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* Can handle slowly varying filter coefficients *
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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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#include "SigProc_FIX.h"
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/* Second order ARMA filter, alternative implementation */
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void silk_biquad_alt(
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const opus_int16 *in, /* I input signal */
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const opus_int32 *B_Q28, /* I MA coefficients [3] */
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const opus_int32 *A_Q28, /* I AR coefficients [2] */
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opus_int32 *S, /* I/O State vector [2] */
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opus_int16 *out, /* O output signal */
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const opus_int32 len, /* I signal length (must be even) */
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opus_int stride /* I Operate on interleaved signal if > 1 */
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)
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{
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/* DIRECT FORM II TRANSPOSED (uses 2 element state vector) */
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opus_int k;
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opus_int32 inval, A0_U_Q28, A0_L_Q28, A1_U_Q28, A1_L_Q28, out32_Q14;
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/* Negate A_Q28 values and split in two parts */
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A0_L_Q28 = ( -A_Q28[ 0 ] ) & 0x00003FFF; /* lower part */
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A0_U_Q28 = silk_RSHIFT( -A_Q28[ 0 ], 14 ); /* upper part */
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A1_L_Q28 = ( -A_Q28[ 1 ] ) & 0x00003FFF; /* lower part */
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A1_U_Q28 = silk_RSHIFT( -A_Q28[ 1 ], 14 ); /* upper part */
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for( k = 0; k < len; k++ ) {
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/* S[ 0 ], S[ 1 ]: Q12 */
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inval = in[ k * stride ];
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out32_Q14 = silk_LSHIFT( silk_SMLAWB( S[ 0 ], B_Q28[ 0 ], inval ), 2 );
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S[ 0 ] = S[1] + silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14, A0_L_Q28 ), 14 );
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S[ 0 ] = silk_SMLAWB( S[ 0 ], out32_Q14, A0_U_Q28 );
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S[ 0 ] = silk_SMLAWB( S[ 0 ], B_Q28[ 1 ], inval);
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S[ 1 ] = silk_RSHIFT_ROUND( silk_SMULWB( out32_Q14, A1_L_Q28 ), 14 );
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S[ 1 ] = silk_SMLAWB( S[ 1 ], out32_Q14, A1_U_Q28 );
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S[ 1 ] = silk_SMLAWB( S[ 1 ], B_Q28[ 2 ], inval );
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/* Scale back to Q0 and saturate */
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out[ k * stride ] = (opus_int16)silk_SAT16( silk_RSHIFT( out32_Q14 + (1<<14) - 1, 14 ) );
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}
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}
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