74 lines
4.0 KiB
C
74 lines
4.0 KiB
C
/***********************************************************************
|
|
Copyright (c) 2006-2010, Skype Limited. All rights reserved.
|
|
Redistribution and use in source and binary forms, with or without
|
|
modification, (subject to the limitations in the disclaimer below)
|
|
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 Skype Limited, nor the names of specific
|
|
contributors, may be used to endorse or promote products derived from
|
|
this software without specific prior written permission.
|
|
NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
|
|
BY THIS LICENSE. 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 LIABLE FOR ANY DIRECT, INDIRECT,
|
|
INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
|
|
NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
|
|
USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
|
|
ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
|
|
(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
|
|
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
|
|
***********************************************************************/
|
|
|
|
/* *
|
|
* SKP_Silk_biquad_alt.c *
|
|
* *
|
|
* Second order ARMA filter *
|
|
* Can handle slowly varying filter coefficients *
|
|
* */
|
|
#include "SKP_Silk_SigProc_FIX.h"
|
|
|
|
|
|
/* Second order ARMA filter, alternative implementation */
|
|
void SKP_Silk_biquad_alt(
|
|
const SKP_int16 *in, /* I: Input signal */
|
|
const SKP_int32 *B_Q28, /* I: MA coefficients [3] */
|
|
const SKP_int32 *A_Q28, /* I: AR coefficients [2] */
|
|
SKP_int32 *S, /* I/O: State vector [2] */
|
|
SKP_int16 *out, /* O: Output signal */
|
|
const SKP_int32 len /* I: Signal length (must be even) */
|
|
)
|
|
{
|
|
/* DIRECT FORM II TRANSPOSED (uses 2 element state vector) */
|
|
SKP_int k;
|
|
SKP_int32 inval, A0_U_Q28, A0_L_Q28, A1_U_Q28, A1_L_Q28, out32_Q14;
|
|
|
|
/* Negate A_Q28 values and split in two parts */
|
|
A0_L_Q28 = ( -A_Q28[ 0 ] ) & 0x00003FFF; /* lower part */
|
|
A0_U_Q28 = SKP_RSHIFT( -A_Q28[ 0 ], 14 ); /* upper part */
|
|
A1_L_Q28 = ( -A_Q28[ 1 ] ) & 0x00003FFF; /* lower part */
|
|
A1_U_Q28 = SKP_RSHIFT( -A_Q28[ 1 ], 14 ); /* upper part */
|
|
|
|
for( k = 0; k < len; k++ ) {
|
|
/* S[ 0 ], S[ 1 ]: Q12 */
|
|
inval = in[ k ];
|
|
out32_Q14 = SKP_LSHIFT( SKP_SMLAWB( S[ 0 ], B_Q28[ 0 ], inval ), 2 );
|
|
|
|
S[ 0 ] = S[1] + SKP_RSHIFT( SKP_SMULWB( out32_Q14, A0_L_Q28 ), 14 );
|
|
S[ 0 ] = SKP_SMLAWB( S[ 0 ], out32_Q14, A0_U_Q28 );
|
|
S[ 0 ] = SKP_SMLAWB( S[ 0 ], B_Q28[ 1 ], inval);
|
|
|
|
S[ 1 ] = SKP_RSHIFT( SKP_SMULWB( out32_Q14, A1_L_Q28 ), 14 );
|
|
S[ 1 ] = SKP_SMLAWB( S[ 1 ], out32_Q14, A1_U_Q28 );
|
|
S[ 1 ] = SKP_SMLAWB( S[ 1 ], B_Q28[ 2 ], inval );
|
|
|
|
/* Scale back to Q0 and saturate */
|
|
out[ k ] = (SKP_int16)SKP_SAT16( SKP_RSHIFT( out32_Q14, 14 ) + 2 );
|
|
}
|
|
}
|