62 lines
3.4 KiB
C
62 lines
3.4 KiB
C
/***********************************************************************
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Copyright (c) 2006-2010, 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_Silk_lowpass_int.c *
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* *
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* First order low-pass filter, with input as SKP_int32, running at *
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* 48 kHz *
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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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/* First order low-pass filter, with input as SKP_int32, running at 48 kHz */
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void SKP_Silk_lowpass_int(
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const SKP_int32 *in, /* I: Q25 48 kHz signal; length = len */
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SKP_int32 *S, /* I/O: Q25 state; length = 1 */
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SKP_int32 *out, /* O: Q25 48 kHz signal; length = len */
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const SKP_int32 len /* I: Number of samples */
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)
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{
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SKP_int k;
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SKP_int32 in_tmp, out_tmp, state;
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state = S[ 0 ];
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for( k = len; k > 0; k-- ) {
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in_tmp = *in++;
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in_tmp -= SKP_RSHIFT( in_tmp, 2 ); /* multiply by 0.75 */
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out_tmp = state + in_tmp; /* zero at nyquist */
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state = in_tmp - SKP_RSHIFT( out_tmp, 1 ); /* pole */
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*out++ = out_tmp;
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}
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S[ 0 ] = state;
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}
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