82 lines
3.4 KiB
C
82 lines
3.4 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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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "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 silk_apply_sine_window_FLP(
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silk_float px_win[], /* O Pointer to windowed signal */
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const silk_float px[], /* I Pointer to input signal */
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const opus_int win_type, /* I Selects a window type */
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const opus_int length /* I Window length, multiple of 4 */
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)
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{
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opus_int k;
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silk_float freq, c, S0, S1;
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silk_assert( win_type == 1 || win_type == 2 );
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/* Length must be multiple of 4 */
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silk_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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