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.h b/modules/audio_processing/ns/fast_math.h
new file mode 100644
index 0000000..0aefee9
--- /dev/null
+++ b/modules/audio_processing/ns/fast_math.h
@@ -0,0 +1,38 @@
+/*
+ * 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.
+ */
+
+#ifndef MODULES_AUDIO_PROCESSING_NS_FAST_MATH_H_
+#define MODULES_AUDIO_PROCESSING_NS_FAST_MATH_H_
+
+#include "api/array_view.h"
+
+namespace webrtc {
+
+// Sqrt approximation.
+float SqrtFastApproximation(float f);
+
+// Log base conversion log(x) = log2(x)/log2(e).
+float LogApproximation(float x);
+void LogApproximation(rtc::ArrayView<const float> x, rtc::ArrayView<float> y);
+
+// 2^x approximation.
+float Pow2Approximation(float p);
+
+// x^p approximation.
+float PowApproximation(float x, float p);
+
+// e^x approximation.
+float ExpApproximation(float x);
+void ExpApproximation(rtc::ArrayView<const float> x, rtc::ArrayView<float> y);
+void ExpApproximationSignFlip(rtc::ArrayView<const float> x,
+ rtc::ArrayView<float> y);
+} // namespace webrtc
+
+#endif // MODULES_AUDIO_PROCESSING_NS_FAST_MATH_H_