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 20 void 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
