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78 lines
3.6 KiB
C
78 lines
3.6 KiB
C
/***********************************************************************
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Copyright (c) 2006-2012, 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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#include "SKP_Silk_main_FLP.h"
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/* Apply sine window to signal vector. */
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/* Window types: */
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/* 1 -> sine window from 0 to pi/2 */
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/* 2 -> sine window from pi/2 to pi */
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void SKP_Silk_apply_sine_window_FLP(
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SKP_float px_win[], /* O Pointer to windowed signal */
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const SKP_float px[], /* I Pointer to input signal */
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const SKP_int win_type, /* I Selects a window type */
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const SKP_int length /* I Window length, multiple of 4 */
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)
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{
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SKP_int k;
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SKP_float freq, c, S0, S1;
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SKP_assert( win_type == 1 || win_type == 2 );
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/* Length must be multiple of 4 */
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SKP_assert( ( length & 3 ) == 0 );
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freq = PI / ( length + 1 );
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/* Approximation of 2 * cos(f) */
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c = 2.0f - freq * freq;
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/* Initialize state */
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if( win_type < 2 ) {
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/* Start from 0 */
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S0 = 0.0f;
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/* Approximation of sin(f) */
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S1 = freq;
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} else {
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/* Start from 1 */
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S0 = 1.0f;
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/* Approximation of cos(f) */
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S1 = 0.5f * c;
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}
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/* Uses the recursive equation: sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f) */
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/* 4 samples at a time */
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for( k = 0; k < length; k += 4 ) {
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px_win[ k + 0 ] = px[ k + 0 ] * 0.5f * ( S0 + S1 );
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px_win[ k + 1 ] = px[ k + 1 ] * S1;
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S0 = c * S1 - S0;
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px_win[ k + 2 ] = px[ k + 2 ] * 0.5f * ( S1 + S0 );
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px_win[ k + 3 ] = px[ k + 3 ] * S0;
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S1 = c * S0 - S1;
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}
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}
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