93 lines
4.7 KiB
C
93 lines
4.7 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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#include "SKP_Silk_SigProc_FIX.h"
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/* Apply sine window to signal vector. */
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/* Window types: */
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/* 0 -> sine window from 0 to pi */
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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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/* every other sample of window is linearly interpolated, for speed */
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void SKP_Silk_apply_sine_window(
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SKP_int16 px_win[], /* O Pointer to windowed signal */
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const SKP_int16 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_int32 px32, f_Q16, c_Q20, S0_Q16, S1_Q16;
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/* Length must be multiple of 4 */
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SKP_assert( ( length & 3 ) == 0 );
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/* Input pointer must be 4-byte aligned */
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SKP_assert( ( (SKP_int64)px & 3 ) == 0 );
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if( win_type == 0 ) {
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f_Q16 = SKP_DIV32_16( 411775, length + 1 ); // 411775 = 2 * 65536 * pi
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} else {
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f_Q16 = SKP_DIV32_16( 205887, length + 1 ); // 205887 = 65536 * pi
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}
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/* factor used for cosine approximation */
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c_Q20 = -SKP_RSHIFT( SKP_MUL( f_Q16, f_Q16 ), 12 );
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/* c_Q20 becomes too large if length is too small */
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SKP_assert( c_Q20 >= -32768 );
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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_Q16 = 0;
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/* approximation of sin(f) */
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S1_Q16 = f_Q16;
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} else {
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/* start from 1 */
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S0_Q16 = ( 1 << 16 );
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/* approximation of cos(f) */
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S1_Q16 = ( 1 << 16 ) + SKP_RSHIFT( c_Q20, 5 );
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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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px32 = *( (SKP_int32 *)&px[ k ] ); /* load two values at once */
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px_win[ k ] = (SKP_int16)SKP_SMULWB( SKP_RSHIFT( S0_Q16 + S1_Q16, 1 ), px32 );
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px_win[ k + 1 ] = (SKP_int16)SKP_SMULWT( S1_Q16, px32 );
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S0_Q16 = SKP_RSHIFT( SKP_MUL( c_Q20, S1_Q16 ), 20 ) + SKP_LSHIFT( S1_Q16, 1 ) - S0_Q16 + 1;
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S0_Q16 = SKP_min( S0_Q16, ( 1 << 16 ) );
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px32 = *( (SKP_int32 *)&px[k + 2] ); /* load two values at once */
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px_win[ k + 2 ] = (SKP_int16)SKP_SMULWB( SKP_RSHIFT( S0_Q16 + S1_Q16, 1 ), px32 );
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px_win[ k + 3 ] = (SKP_int16)SKP_SMULWT( S0_Q16, px32 );
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S1_Q16 = SKP_RSHIFT( SKP_MUL( c_Q20, S0_Q16 ), 20 ) + SKP_LSHIFT( S0_Q16, 1 ) - S1_Q16;
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S1_Q16 = SKP_min( S1_Q16, ( 1 << 16 ) );
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}
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}
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