1 /*
2  *  Copyright (c) 2011 The WebRTC project authors. All Rights Reserved.
3  *
4  *  Use of this source code is governed by a BSD-style license
5  *  that can be found in the LICENSE file in the root of the source
6  *  tree. An additional intellectual property rights grant can be found
7  *  in the file PATENTS.  All contributing project authors may
8  *  be found in the AUTHORS file in the root of the source tree.
9  */
10 
11 
12 /*
13  * This file contains the function WebRtcSpl_SqrtOfOneMinusXSquared().
14  * The description header can be found in signal_processing_library.h
15  *
16  */
17 
18 #include "webrtc/common_audio/signal_processing/include/signal_processing_library.h"
19 
WebRtcSpl_SqrtOfOneMinusXSquared(int16_t * xQ15,size_t vector_length,int16_t * yQ15)20 void WebRtcSpl_SqrtOfOneMinusXSquared(int16_t *xQ15, size_t vector_length,
21                                       int16_t *yQ15)
22 {
23     int32_t sq;
24     size_t m;
25     int16_t tmp;
26 
27     for (m = 0; m < vector_length; m++)
28     {
29         tmp = xQ15[m];
30         sq = tmp * tmp;  // x^2 in Q30
31         sq = 1073741823 - sq; // 1-x^2, where 1 ~= 0.99999999906 is 1073741823 in Q30
32         sq = WebRtcSpl_Sqrt(sq); // sqrt(1-x^2) in Q15
33         yQ15[m] = (int16_t)sq;
34     }
35 }
36