Line data    Source code

       1             : /***********************************************************************
       2             : Copyright (c) 2006-2011, Skype Limited. All rights reserved.
       3             : Redistribution and use in source and binary forms, with or without
       4             : modification, are permitted provided that the following conditions
       5             : are met:
       6             : - Redistributions of source code must retain the above copyright notice,
       7             : this list of conditions and the following disclaimer.
       8             : - Redistributions in binary form must reproduce the above copyright
       9             : notice, this list of conditions and the following disclaimer in the
      10             : documentation and/or other materials provided with the distribution.
      11             : - Neither the name of Internet Society, IETF or IETF Trust, nor the
      12             : names of specific contributors, may be used to endorse or promote
      13             : products derived from this software without specific prior written
      14             : permission.
      15             : THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
      16             : AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
      17             : IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
      18             : ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
      19             : LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
      20             : CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
      21             : SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
      22             : INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
      23             : CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
      24             : ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
      25             : POSSIBILITY OF SUCH DAMAGE.
      26             : ***********************************************************************/
      27             : 
      28             : #ifdef HAVE_CONFIG_H
      29             : #include "config.h"
      30             : #endif
      31             : 
      32             : #include "main_FLP.h"
      33             : 
      34             : /* Apply sine window to signal vector   */
      35             : /* Window types:                        */
      36             : /*  1 -> sine window from 0 to pi/2     */
      37             : /*  2 -> sine window from pi/2 to pi    */
      38           0 : void silk_apply_sine_window_FLP(
      39             :     silk_float                      px_win[],                           /* O    Pointer to windowed signal                  */
      40             :     const silk_float                px[],                               /* I    Pointer to input signal                     */
      41             :     const opus_int                  win_type,                           /* I    Selects a window type                       */
      42             :     const opus_int                  length                              /* I    Window length, multiple of 4                */
      43             : )
      44             : {
      45             :     opus_int   k;
      46             :     silk_float freq, c, S0, S1;
      47             : 
      48           0 :     silk_assert( win_type == 1 || win_type == 2 );
      49             : 
      50             :     /* Length must be multiple of 4 */
      51           0 :     silk_assert( ( length & 3 ) == 0 );
      52             : 
      53           0 :     freq = PI / ( length + 1 );
      54             : 
      55             :     /* Approximation of 2 * cos(f) */
      56           0 :     c = 2.0f - freq * freq;
      57             : 
      58             :     /* Initialize state */
      59           0 :     if( win_type < 2 ) {
      60             :         /* Start from 0 */
      61           0 :         S0 = 0.0f;
      62             :         /* Approximation of sin(f) */
      63           0 :         S1 = freq;
      64             :     } else {
      65             :         /* Start from 1 */
      66           0 :         S0 = 1.0f;
      67             :         /* Approximation of cos(f) */
      68           0 :         S1 = 0.5f * c;
      69             :     }
      70             : 
      71             :     /* Uses the recursive equation:   sin(n*f) = 2 * cos(f) * sin((n-1)*f) - sin((n-2)*f)   */
      72             :     /* 4 samples at a time */
      73           0 :     for( k = 0; k < length; k += 4 ) {
      74           0 :         px_win[ k + 0 ] = px[ k + 0 ] * 0.5f * ( S0 + S1 );
      75           0 :         px_win[ k + 1 ] = px[ k + 1 ] * S1;
      76           0 :         S0 = c * S1 - S0;
      77           0 :         px_win[ k + 2 ] = px[ k + 2 ] * 0.5f * ( S1 + S0 );
      78           0 :         px_win[ k + 3 ] = px[ k + 3 ] * S0;
      79           0 :         S1 = c * S0 - S1;
      80             :     }
      81           0 : }