| /* |
| * 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. |
| */ |
| |
| #include <cmath> |
| |
| #include "webrtc/modules/audio_coding/audio_network_adaptor/smoothing_filter.h" |
| |
| namespace webrtc { |
| |
| SmoothingFilterImpl::SmoothingFilterImpl(int time_constant_ms, |
| const Clock* clock) |
| : time_constant_ms_(time_constant_ms), |
| clock_(clock), |
| first_sample_received_(false), |
| initialized_(false), |
| first_sample_time_ms_(0), |
| last_sample_time_ms_(0), |
| filter_(0.0) {} |
| |
| void SmoothingFilterImpl::AddSample(float sample) { |
| if (!first_sample_received_) { |
| last_sample_time_ms_ = first_sample_time_ms_ = clock_->TimeInMilliseconds(); |
| first_sample_received_ = true; |
| RTC_DCHECK_EQ(rtc::ExpFilter::kValueUndefined, filter_.filtered()); |
| |
| // Since this is first sample, any value for argument 1 should work. |
| filter_.Apply(0.0f, sample); |
| return; |
| } |
| |
| int64_t now_ms = clock_->TimeInMilliseconds(); |
| if (!initialized_) { |
| float duration = now_ms - first_sample_time_ms_; |
| if (duration < static_cast<int64_t>(time_constant_ms_)) { |
| filter_.UpdateBase(exp(1.0f / duration)); |
| } else { |
| initialized_ = true; |
| filter_.UpdateBase(exp(1.0f / time_constant_ms_)); |
| } |
| } |
| |
| // The filter will do the following: |
| // float alpha = pow(base, last_update_time_ms_ - now_ms); |
| // filtered_ = alpha * filtered_ + (1 - alpha) * sample; |
| filter_.Apply(static_cast<float>(last_sample_time_ms_ - now_ms), sample); |
| last_sample_time_ms_ = now_ms; |
| } |
| |
| rtc::Optional<float> SmoothingFilterImpl::GetAverage() const { |
| float value = filter_.filtered(); |
| return value == rtc::ExpFilter::kValueUndefined ? rtc::Optional<float>() |
| : rtc::Optional<float>(value); |
| } |
| |
| } // namespace webrtc |