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 "signal_processing_library.h"
19
20void WebRtcSpl_SqrtOfOneMinusXSquared(WebRtc_Word16 *xQ15, int vector_length,
21                                      WebRtc_Word16 *yQ15)
22{
23    WebRtc_Word32 sq;
24    int m;
25    WebRtc_Word16 tmp;
26
27    for (m = 0; m < vector_length; m++)
28    {
29        tmp = xQ15[m];
30        sq = WEBRTC_SPL_MUL_16_16(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] = (WebRtc_Word16)sq;
34    }
35}
36