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