Reland "Refactoring of the noise suppressor and adding true multichannel support"
This is a reland of 87a7b82520b83a6cf42da27cdc46142c2eb6248c
Original change's description:
> Refactoring of the noise suppressor and adding true multichannel support
>
> This CL adds proper multichannel support to the noise suppressor.
> To accomplish that in a safe way, a full refactoring of the noise
> suppressor code has been done.
>
> Due to floating point precision, the changes made are not entirely
> bitexact. They are, however, very close to being bitexact.
>
> As a safety measure, the former noise suppressor code is preserved
> and a kill-switch is added to allow revering to the legacy noise
> suppressor in case issues arise.
>
> Bug: webrtc:10895, b/143344262
> Change-Id: I0b071011b23265ac12e6d4b3956499d122286657
> Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158407
> Commit-Queue: Per Åhgren <peah@webrtc.org>
> Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
> Cr-Commit-Position: refs/heads/master@{#29646}
Bug: webrtc:10895, b/143344262
Change-Id: I236f1e67bb0baa4e30908a4cf7a8a7bb55fbced3
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/158747
Reviewed-by: Gustaf Ullberg <gustaf@webrtc.org>
Commit-Queue: Per Åhgren <peah@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#29663}
diff --git a/modules/audio_processing/ns/fast_math.cc b/modules/audio_processing/ns/fast_math.cc
new file mode 100644
index 0000000..d13110c
--- /dev/null
+++ b/modules/audio_processing/ns/fast_math.cc
@@ -0,0 +1,84 @@
+/*
+ * 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 <math.h>
+#include <stdint.h>
+
+#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<const float> x, rtc::ArrayView<float> 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<const float> x, rtc::ArrayView<float> y) {
+ for (size_t k = 0; k < x.size(); ++k) {
+ y[k] = ExpApproximation(x[k]);
+ }
+}
+
+void ExpApproximationSignFlip(rtc::ArrayView<const float> x,
+ rtc::ArrayView<float> y) {
+ for (size_t k = 0; k < x.size(); ++k) {
+ y[k] = ExpApproximation(-x[k]);
+ }
+}
+
+} // namespace webrtc