81 lines
4.2 KiB
C
81 lines
4.2 KiB
C
/***********************************************************************
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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, (subject to the limitations in the disclaimer below)
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are permitted provided that the following conditions 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 Skype Limited, nor the names of specific
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contributors, may be used to endorse or promote products derived from
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this software without specific prior written permission.
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NO EXPRESS OR IMPLIED LICENSES TO ANY PARTY'S PATENT RIGHTS ARE GRANTED
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BY THIS LICENSE. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND
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CONTRIBUTORS ''AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
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BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
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FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
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COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
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INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
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NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF
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USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON
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ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
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(INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
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OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
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***********************************************************************/
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/* *
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* SKP_ana_filt_bank_1.c *
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* *
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* Split signal into two decimated bands using first-order allpass filters *
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* *
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* Copyright 2006 (c), Skype Limited *
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* Date: 060221 *
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* */
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#include "SKP_Silk_SigProc_FIX.h"
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/* Coefficients for 2-band filter bank based on first-order allpass filters */
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// old
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static SKP_int16 A_fb1_20[ 1 ] = { 5394 << 1 };
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static SKP_int16 A_fb1_21[ 1 ] = { 20623 << 1 }; /* wrap-around to negative number is intentional */
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/* Split signal into two decimated bands using first-order allpass filters */
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void SKP_Silk_ana_filt_bank_1(
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const SKP_int16 *in, /* I: Input signal [N] */
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SKP_int32 *S, /* I/O: State vector [2] */
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SKP_int16 *outL, /* O: Low band [N/2] */
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SKP_int16 *outH, /* O: High band [N/2] */
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SKP_int32 *scratch, /* I: Scratch memory [3*N/2] */ // todo: remove - no longer used
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const SKP_int32 N /* I: Number of input samples */
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)
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{
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SKP_int k, N2 = SKP_RSHIFT( N, 1 );
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SKP_int32 in32, X, Y, out_1, out_2;
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/* Internal variables and state are in Q10 format */
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for( k = 0; k < N2; k++ ) {
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/* Convert to Q10 */
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in32 = SKP_LSHIFT( (SKP_int32)in[ 2 * k ], 10 );
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/* All-pass section for even input sample */
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Y = SKP_SUB32( in32, S[ 0 ] );
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X = SKP_SMLAWB( Y, Y, A_fb1_21[ 0 ] );
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out_1 = SKP_ADD32( S[ 0 ], X );
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S[ 0 ] = SKP_ADD32( in32, X );
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/* Convert to Q10 */
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in32 = SKP_LSHIFT( (SKP_int32)in[ 2 * k + 1 ], 10 );
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/* All-pass section for odd input sample */
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Y = SKP_SUB32( in32, S[ 1 ] );
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X = SKP_SMULWB( Y, A_fb1_20[ 0 ] );
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out_2 = SKP_ADD32( S[ 1 ], X );
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S[ 1 ] = SKP_ADD32( in32, X );
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/* Add/subtract, convert back to int16 and store to output */
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outL[ k ] = (SKP_int16)SKP_SAT16( SKP_RSHIFT_ROUND( SKP_ADD32( out_2, out_1 ), 11 ) );
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outH[ k ] = (SKP_int16)SKP_SAT16( SKP_RSHIFT_ROUND( SKP_SUB32( out_2, out_1 ), 11 ) );
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}
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}
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