1e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent/* 2e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * Copyright (c) 2011 The WebRTC project authors. All Rights Reserved. 3e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * 4e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * Use of this source code is governed by a BSD-style license 5e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * that can be found in the LICENSE file in the root of the source 6e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * tree. An additional intellectual property rights grant can be found 7e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * in the file PATENTS. All contributing project authors may 8e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * be found in the AUTHORS file in the root of the source tree. 9e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent */ 10e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent 11e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent 12e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent/* 13e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * This file contains the function WebRtcSpl_SqrtOfOneMinusXSquared(). 14e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * The description header can be found in signal_processing_library.h 15e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent * 16e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent */ 17e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent 18e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent#include "signal_processing_library.h" 19e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent 20e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurentvoid WebRtcSpl_SqrtOfOneMinusXSquared(WebRtc_Word16 *xQ15, int vector_length, 21e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent WebRtc_Word16 *yQ15) 22e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent{ 23e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent WebRtc_Word32 sq; 24e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent int m; 25e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent WebRtc_Word16 tmp; 26e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent 27e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent for (m = 0; m < vector_length; m++) 28e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent { 29e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent tmp = xQ15[m]; 30e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent sq = WEBRTC_SPL_MUL_16_16(tmp, tmp); // x^2 in Q30 31e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent sq = 1073741823 - sq; // 1-x^2, where 1 ~= 0.99999999906 is 1073741823 in Q30 32e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent sq = WebRtcSpl_Sqrt(sq); // sqrt(1-x^2) in Q15 33e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent yQ15[m] = (WebRtc_Word16)sq; 34e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent } 35e48d5845c8b35de2ab73ea055c18a61fa3a9f0beEric Laurent} 36