| /* |
| * Copyright (c) 2016 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 WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_SMOOTHING_FILTER_H_ |
| #define WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_SMOOTHING_FILTER_H_ |
| |
| #include "webrtc/base/constructormagic.h" |
| #include "webrtc/base/exp_filter.h" |
| #include "webrtc/base/optional.h" |
| #include "webrtc/system_wrappers/include/clock.h" |
| |
| namespace webrtc { |
| |
| class SmoothingFilter { |
| public: |
| virtual ~SmoothingFilter() = default; |
| virtual void AddSample(float sample) = 0; |
| virtual rtc::Optional<float> GetAverage() const = 0; |
| }; |
| |
| // SmoothingFilterImpl applies an exponential filter |
| // alpha = exp(-sample_interval / time_constant); |
| // y[t] = alpha * y[t-1] + (1 - alpha) * sample; |
| class SmoothingFilterImpl final : public SmoothingFilter { |
| public: |
| // |time_constant_ms| is the time constant for the exponential filter. |
| SmoothingFilterImpl(int time_constant_ms, const Clock* clock); |
| |
| void AddSample(float sample) override; |
| rtc::Optional<float> GetAverage() const override; |
| |
| private: |
| const int time_constant_ms_; |
| const Clock* const clock_; |
| |
| bool first_sample_received_; |
| bool initialized_; |
| int64_t first_sample_time_ms_; |
| int64_t last_sample_time_ms_; |
| rtc::ExpFilter filter_; |
| |
| RTC_DISALLOW_COPY_AND_ASSIGN(SmoothingFilterImpl); |
| }; |
| |
| } // namespace webrtc |
| |
| #endif // WEBRTC_MODULES_AUDIO_CODING_AUDIO_NETWORK_ADAPTOR_SMOOTHING_FILTER_H_ |