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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 "modules/audio_processing/aec3/multi_channel_content_detector.h"
#include <cmath>
#include "rtc_base/checks.h"
namespace webrtc {
namespace {
constexpr int kNumFramesPerSecond = 100;
// Compares the left and right channels in the render `frame` to determine
// whether the signal is a proper stereo signal. To allow for differences
// introduced by hardware drivers, a threshold `detection_threshold` is used for
// the detection.
bool HasStereoContent(const std::vector<std::vector<std::vector<float>>>& frame,
float detection_threshold) {
if (frame[0].size() < 2) {
return false;
}
for (size_t band = 0; band < frame.size(); ++band) {
for (size_t k = 0; k < frame[band][0].size(); ++k) {
if (std::fabs(frame[band][0][k] - frame[band][1][k]) >
detection_threshold) {
return true;
}
}
}
return false;
}
} // namespace
MultiChannelContentDetector::MultiChannelContentDetector(
bool detect_stereo_content,
int num_render_input_channels,
float detection_threshold,
int stereo_detection_timeout_threshold_seconds,
float stereo_detection_hysteresis_seconds)
: detect_stereo_content_(detect_stereo_content),
detection_threshold_(detection_threshold),
detection_timeout_threshold_frames_(
stereo_detection_timeout_threshold_seconds > 0
? absl::make_optional(stereo_detection_timeout_threshold_seconds *
kNumFramesPerSecond)
: absl::nullopt),
stereo_detection_hysteresis_frames_(static_cast<int>(
stereo_detection_hysteresis_seconds * kNumFramesPerSecond)),
persistent_multichannel_content_detected_(
!detect_stereo_content && num_render_input_channels > 1) {}
bool MultiChannelContentDetector::UpdateDetection(
const std::vector<std::vector<std::vector<float>>>& frame) {
if (!detect_stereo_content_) {
RTC_DCHECK_EQ(frame[0].size() > 1,
persistent_multichannel_content_detected_);
return false;
}
const bool previous_persistent_multichannel_content_detected =
persistent_multichannel_content_detected_;
const bool stereo_detected_in_frame =
HasStereoContent(frame, detection_threshold_);
consecutive_frames_with_stereo_ =
stereo_detected_in_frame ? consecutive_frames_with_stereo_ + 1 : 0;
frames_since_stereo_detected_last_ =
stereo_detected_in_frame ? 0 : frames_since_stereo_detected_last_ + 1;
// Detect persistent multichannel content.
if (consecutive_frames_with_stereo_ > stereo_detection_hysteresis_frames_) {
persistent_multichannel_content_detected_ = true;
}
if (detection_timeout_threshold_frames_.has_value() &&
frames_since_stereo_detected_last_ >=
*detection_timeout_threshold_frames_) {
persistent_multichannel_content_detected_ = false;
}
// Detect temporary multichannel content.
temporary_multichannel_content_detected_ =
persistent_multichannel_content_detected_ ? false
: stereo_detected_in_frame;
return previous_persistent_multichannel_content_detected !=
persistent_multichannel_content_detected_;
}
} // namespace webrtc
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