ref: 1632152b83b8ab4e28393bca94450796b71b0201
dir: /silk/float/apply_sine_window_FLP.c/
/*********************************************************************** Copyright (c) 2006-2011, Skype Limited. All rights reserved. Redistribution and use in source and binary forms, with or without modification, are permitted provided that the following conditions are met: - Redistributions of source code must retain the above copyright notice, this list of conditions and the following disclaimer. - Redistributions in binary form must reproduce the above copyright notice, this list of conditions and the following disclaimer in the documentation and/or other materials provided with the distribution. - Neither the name of Internet Society, IETF or IETF Trust, nor the names of specific contributors, may be used to endorse or promote products derived from this software without specific prior written permission. THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. ***********************************************************************/ #ifdef HAVE_CONFIG_H #include "config.h" #endif #include "main_FLP.h" /* Apply sine window to signal vector */ /* Window types: */ /* 1 -> sine window from 0 to pi/2 */ /* 2 -> sine window from pi/2 to pi */ void silk_apply_sine_window_FLP( silk_float px_win[], /* O Pointer to windowed signal */ const silk_float px[], /* I Pointer to input signal */ const opus_int win_type, /* I Selects a window type */ const opus_int length /* I Window length, multiple of 4 */ ) { opus_int k; silk_float freq, c, S0, S1; silk_assert( win_type == 1 || win_type == 2 ); /* Length must be multiple of 4 */ silk_assert( ( length & 3 ) == 0 ); freq = PI / ( length + 1 ); /* Approximation of 2 * cos(f) */ c = 2.0f - freq * freq; /* Initialize state */ if( win_type < 2 ) { /* Start from 0 */ S0 = 0.0f; /* Approximation of sin(f) */ S1 = freq; } else { /* Start from 1 */ S0 = 1.0f; /* Approximation of cos(f) */ S1 = 0.5f * c; } /* Uses the recursive equation: sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f) */ /* 4 samples at a time */ for( k = 0; k < length; k += 4 ) { px_win[ k + 0 ] = px[ k + 0 ] * 0.5f * ( S0 + S1 ); px_win[ k + 1 ] = px[ k + 1 ] * S1; S0 = c * S1 - S0; px_win[ k + 2 ] = px[ k + 2 ] * 0.5f * ( S1 + S0 ); px_win[ k + 3 ] = px[ k + 3 ] * S0; S1 = c * S0 - S1; } }