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 /* * Copyright (c) 2019 The WebRTC project authors. All Rights Reserved. * * Use of this source code is governed by a BSD-style license * that can be found in the LICENSE file in the root of the source * tree. An additional intellectual property rights grant can be found * in the file PATENTS. All contributing project authors may * be found in the AUTHORS file in the root of the source tree. */ #include "modules/audio_processing/ns/fast_math.h" #include #include #include "rtc_base/checks.h" namespace webrtc { namespace { float FastLog2f(float in) { RTC_DCHECK_GT(in, .0f); // Read and interpret float as uint32_t and then cast to float. // This is done to extract the exponent (bits 30 - 23). // "Right shift" of the exponent is then performed by multiplying // with the constant (1/2^23). Finally, we subtract a constant to // remove the bias (https://en.wikipedia.org/wiki/Exponent_bias). union { float dummy; uint32_t a; } x = {in}; float out = x.a; out *= 1.1920929e-7f; // 1/2^23 out -= 126.942695f; // Remove bias. return out; } } // namespace float SqrtFastApproximation(float f) { // TODO(peah): Add fast approximate implementation. return sqrtf(f); } float Pow2Approximation(float p) { // TODO(peah): Add fast approximate implementation. return powf(2.f, p); } float PowApproximation(float x, float p) { return Pow2Approximation(p * FastLog2f(x)); } float LogApproximation(float x) { constexpr float kLogOf2 = 0.69314718056f; return FastLog2f(x) * kLogOf2; } void LogApproximation(rtc::ArrayView x, rtc::ArrayView y) { for (size_t k = 0; k < x.size(); ++k) { y[k] = LogApproximation(x[k]); } } float ExpApproximation(float x) { constexpr float kLog10Ofe = 0.4342944819f; return PowApproximation(10.f, x * kLog10Ofe); } void ExpApproximation(rtc::ArrayView x, rtc::ArrayView y) { for (size_t k = 0; k < x.size(); ++k) { y[k] = ExpApproximation(x[k]); } } void ExpApproximationSignFlip(rtc::ArrayView x, rtc::ArrayView y) { for (size_t k = 0; k < x.size(); ++k) { y[k] = ExpApproximation(-x[k]); } } } // namespace webrtc