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* Copyright (c) 2022 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 <stddef.h>
#include <memory>
#include <vector>
#include "absl/types/optional.h"
namespace webrtc {
// Analyzes audio content to determine whether the contained audio is proper
// multichannel, or only upmixed mono. To allow for differences introduced by
// hardware drivers, a threshold `detection_threshold` is used for the
// detection.
// Logs metrics continously and upon destruction.
class MultiChannelContentDetector {
// If |stereo_detection_timeout_threshold_seconds| <= 0, no timeout is
// applied: Once multichannel is detected, the detector remains in that state
// for its lifetime.
MultiChannelContentDetector(bool detect_stereo_content,
int num_render_input_channels,
float detection_threshold,
int stereo_detection_timeout_threshold_seconds,
float stereo_detection_hysteresis_seconds);
// Compares the left and right channels in the render `frame` to determine
// whether the signal is a proper multichannel signal. Returns a bool
// indicating whether a change in the proper multichannel content was
// detected.
bool UpdateDetection(
const std::vector<std::vector<std::vector<float>>>& frame);
bool IsProperMultiChannelContentDetected() const {
return persistent_multichannel_content_detected_;
bool IsTemporaryMultiChannelContentDetected() const {
return temporary_multichannel_content_detected_;
// Tracks and logs metrics for the amount of multichannel content detected.
class MetricsLogger {
// The destructor logs call summary statistics.
// Updates and logs metrics.
void Update(bool persistent_multichannel_content_detected);
int frame_counter_ = 0;
// Counts the number of frames of persistent multichannel audio observed
// during the current metrics collection interval.
int persistent_multichannel_frame_counter_ = 0;
// Indicates whether persistent multichannel content has ever been detected.
bool any_multichannel_content_detected_ = false;
const bool detect_stereo_content_;
const float detection_threshold_;
const absl::optional<int> detection_timeout_threshold_frames_;
const int stereo_detection_hysteresis_frames_;
// Collects and reports metrics on the amount of multichannel content
// detected. Only created if |num_render_input_channels| > 1 and
// |detect_stereo_content_| is true.
const std::unique_ptr<MetricsLogger> metrics_logger_;
bool persistent_multichannel_content_detected_;
bool temporary_multichannel_content_detected_ = false;
int64_t frames_since_stereo_detected_last_ = 0;
int64_t consecutive_frames_with_stereo_ = 0;
} // namespace webrtc