diff options
Diffstat (limited to 'third_party/libwebrtc/modules/audio_processing/aec3/comfort_noise_generator.cc')
-rw-r--r-- | third_party/libwebrtc/modules/audio_processing/aec3/comfort_noise_generator.cc | 186 |
1 files changed, 186 insertions, 0 deletions
diff --git a/third_party/libwebrtc/modules/audio_processing/aec3/comfort_noise_generator.cc b/third_party/libwebrtc/modules/audio_processing/aec3/comfort_noise_generator.cc new file mode 100644 index 0000000000..de5227c089 --- /dev/null +++ b/third_party/libwebrtc/modules/audio_processing/aec3/comfort_noise_generator.cc @@ -0,0 +1,186 @@ +/* + * Copyright (c) 2017 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/aec3/comfort_noise_generator.h" + +// Defines WEBRTC_ARCH_X86_FAMILY, used below. +#include "rtc_base/system/arch.h" + +#if defined(WEBRTC_ARCH_X86_FAMILY) +#include <emmintrin.h> +#endif +#include <algorithm> +#include <array> +#include <cmath> +#include <cstdint> +#include <functional> +#include <numeric> + +#include "common_audio/signal_processing/include/signal_processing_library.h" +#include "modules/audio_processing/aec3/vector_math.h" +#include "rtc_base/checks.h" + +namespace webrtc { + +namespace { + +// Computes the noise floor value that matches a WGN input of noise_floor_dbfs. +float GetNoiseFloorFactor(float noise_floor_dbfs) { + // kdBfsNormalization = 20.f*log10(32768.f). + constexpr float kdBfsNormalization = 90.30899869919436f; + return 64.f * powf(10.f, (kdBfsNormalization + noise_floor_dbfs) * 0.1f); +} + +// Table of sqrt(2) * sin(2*pi*i/32). +constexpr float kSqrt2Sin[32] = { + +0.0000000f, +0.2758994f, +0.5411961f, +0.7856950f, +1.0000000f, + +1.1758756f, +1.3065630f, +1.3870398f, +1.4142136f, +1.3870398f, + +1.3065630f, +1.1758756f, +1.0000000f, +0.7856950f, +0.5411961f, + +0.2758994f, +0.0000000f, -0.2758994f, -0.5411961f, -0.7856950f, + -1.0000000f, -1.1758756f, -1.3065630f, -1.3870398f, -1.4142136f, + -1.3870398f, -1.3065630f, -1.1758756f, -1.0000000f, -0.7856950f, + -0.5411961f, -0.2758994f}; + +void GenerateComfortNoise(Aec3Optimization optimization, + const std::array<float, kFftLengthBy2Plus1>& N2, + uint32_t* seed, + FftData* lower_band_noise, + FftData* upper_band_noise) { + FftData* N_low = lower_band_noise; + FftData* N_high = upper_band_noise; + + // Compute square root spectrum. + std::array<float, kFftLengthBy2Plus1> N; + std::copy(N2.begin(), N2.end(), N.begin()); + aec3::VectorMath(optimization).Sqrt(N); + + // Compute the noise level for the upper bands. + constexpr float kOneByNumBands = 1.f / (kFftLengthBy2Plus1 / 2 + 1); + constexpr int kFftLengthBy2Plus1By2 = kFftLengthBy2Plus1 / 2; + const float high_band_noise_level = + std::accumulate(N.begin() + kFftLengthBy2Plus1By2, N.end(), 0.f) * + kOneByNumBands; + + // The analysis and synthesis windowing cause loss of power when + // cross-fading the noise where frames are completely uncorrelated + // (generated with random phase), hence the factor sqrt(2). + // This is not the case for the speech signal where the input is overlapping + // (strong correlation). + N_low->re[0] = N_low->re[kFftLengthBy2] = N_high->re[0] = + N_high->re[kFftLengthBy2] = 0.f; + for (size_t k = 1; k < kFftLengthBy2; k++) { + constexpr int kIndexMask = 32 - 1; + // Generate a random 31-bit integer. + seed[0] = (seed[0] * 69069 + 1) & (0x80000000 - 1); + // Convert to a 5-bit index. + int i = seed[0] >> 26; + + // y = sqrt(2) * sin(a) + const float x = kSqrt2Sin[i]; + // x = sqrt(2) * cos(a) = sqrt(2) * sin(a + pi/2) + const float y = kSqrt2Sin[(i + 8) & kIndexMask]; + + // Form low-frequency noise via spectral shaping. + N_low->re[k] = N[k] * x; + N_low->im[k] = N[k] * y; + + // Form the high-frequency noise via simple levelling. + N_high->re[k] = high_band_noise_level * x; + N_high->im[k] = high_band_noise_level * y; + } +} + +} // namespace + +ComfortNoiseGenerator::ComfortNoiseGenerator(const EchoCanceller3Config& config, + Aec3Optimization optimization, + size_t num_capture_channels) + : optimization_(optimization), + seed_(42), + num_capture_channels_(num_capture_channels), + noise_floor_(GetNoiseFloorFactor(config.comfort_noise.noise_floor_dbfs)), + N2_initial_( + std::make_unique<std::vector<std::array<float, kFftLengthBy2Plus1>>>( + num_capture_channels_)), + Y2_smoothed_(num_capture_channels_), + N2_(num_capture_channels_) { + for (size_t ch = 0; ch < num_capture_channels_; ++ch) { + (*N2_initial_)[ch].fill(0.f); + Y2_smoothed_[ch].fill(0.f); + N2_[ch].fill(1.0e6f); + } +} + +ComfortNoiseGenerator::~ComfortNoiseGenerator() = default; + +void ComfortNoiseGenerator::Compute( + bool saturated_capture, + rtc::ArrayView<const std::array<float, kFftLengthBy2Plus1>> + capture_spectrum, + rtc::ArrayView<FftData> lower_band_noise, + rtc::ArrayView<FftData> upper_band_noise) { + const auto& Y2 = capture_spectrum; + + if (!saturated_capture) { + // Smooth Y2. + for (size_t ch = 0; ch < num_capture_channels_; ++ch) { + std::transform(Y2_smoothed_[ch].begin(), Y2_smoothed_[ch].end(), + Y2[ch].begin(), Y2_smoothed_[ch].begin(), + [](float a, float b) { return a + 0.1f * (b - a); }); + } + + if (N2_counter_ > 50) { + // Update N2 from Y2_smoothed. + for (size_t ch = 0; ch < num_capture_channels_; ++ch) { + std::transform(N2_[ch].begin(), N2_[ch].end(), Y2_smoothed_[ch].begin(), + N2_[ch].begin(), [](float a, float b) { + return b < a ? (0.9f * b + 0.1f * a) * 1.0002f + : a * 1.0002f; + }); + } + } + + if (N2_initial_) { + if (++N2_counter_ == 1000) { + N2_initial_.reset(); + } else { + // Compute the N2_initial from N2. + for (size_t ch = 0; ch < num_capture_channels_; ++ch) { + std::transform(N2_[ch].begin(), N2_[ch].end(), + (*N2_initial_)[ch].begin(), (*N2_initial_)[ch].begin(), + [](float a, float b) { + return a > b ? b + 0.001f * (a - b) : a; + }); + } + } + } + + for (size_t ch = 0; ch < num_capture_channels_; ++ch) { + for (auto& n : N2_[ch]) { + n = std::max(n, noise_floor_); + } + if (N2_initial_) { + for (auto& n : (*N2_initial_)[ch]) { + n = std::max(n, noise_floor_); + } + } + } + } + + // Choose N2 estimate to use. + const auto& N2 = N2_initial_ ? (*N2_initial_) : N2_; + + for (size_t ch = 0; ch < num_capture_channels_; ++ch) { + GenerateComfortNoise(optimization_, N2[ch], &seed_, &lower_band_noise[ch], + &upper_band_noise[ch]); + } +} + +} // namespace webrtc |