jamulus/libs/opus/silk/float/apply_sine_window_FLP.c
2013-12-21 13:40:43 +00:00

81 lines
3.4 KiB
C
Executable file

/***********************************************************************
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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
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***********************************************************************/
#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;
}
}