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/*
* Copyright (c) 2014 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 "webrtc/modules/video_coding/utility/quality_scaler.h"
namespace webrtc {
static const int kMinFps = 10;
static const int kMeasureSeconds = 5;
static const int kFramedropPercentThreshold = 60;
static const int kLowQpThresholdDenominator = 3;
QualityScaler::QualityScaler()
: num_samples_(0), low_qp_threshold_(-1), downscale_shift_(0) {
}
void QualityScaler::Init(int max_qp) {
ClearSamples();
downscale_shift_ = 0;
low_qp_threshold_ = max_qp / kLowQpThresholdDenominator ;
}
void QualityScaler::ReportFramerate(int framerate) {
num_samples_ = static_cast<size_t>(
kMeasureSeconds * (framerate < kMinFps ? kMinFps : framerate));
}
void QualityScaler::ReportEncodedFrame(int qp) {
average_qp_.AddSample(qp);
framedrop_percent_.AddSample(0);
}
void QualityScaler::ReportDroppedFrame() {
framedrop_percent_.AddSample(100);
}
QualityScaler::Resolution QualityScaler::GetScaledResolution(
const I420VideoFrame& frame) {
// Both of these should be set through InitEncode -> Should be set by now.
assert(low_qp_threshold_ >= 0);
assert(num_samples_ > 0);
// Update scale factor.
int avg;
if (framedrop_percent_.GetAverage(num_samples_, &avg) &&
avg >= kFramedropPercentThreshold) {
AdjustScale(false);
} else if (average_qp_.GetAverage(num_samples_, &avg) &&
avg <= low_qp_threshold_) {
AdjustScale(true);
}
Resolution res;
res.width = frame.width();
res.height = frame.height();
assert(downscale_shift_ >= 0);
for (int shift = downscale_shift_;
shift > 0 && res.width > 1 && res.height > 1;
--shift) {
res.width >>= 1;
res.height >>= 1;
}
return res;
}
const I420VideoFrame& QualityScaler::GetScaledFrame(
const I420VideoFrame& frame) {
Resolution res = GetScaledResolution(frame);
if (res.width == frame.width())
return frame;
scaler_.Set(frame.width(),
frame.height(),
res.width,
res.height,
kI420,
kI420,
kScaleBox);
if (scaler_.Scale(frame, &scaled_frame_) != 0)
return frame;
scaled_frame_.set_ntp_time_ms(frame.ntp_time_ms());
scaled_frame_.set_timestamp(frame.timestamp());
scaled_frame_.set_render_time_ms(frame.render_time_ms());
return scaled_frame_;
}
QualityScaler::MovingAverage::MovingAverage() : sum_(0) {
}
void QualityScaler::MovingAverage::AddSample(int sample) {
samples_.push_back(sample);
sum_ += sample;
}
bool QualityScaler::MovingAverage::GetAverage(size_t num_samples, int* avg) {
assert(num_samples > 0);
if (num_samples > samples_.size())
return false;
// Remove old samples.
while (num_samples < samples_.size()) {
sum_ -= samples_.front();
samples_.pop_front();
}
*avg = sum_ / static_cast<int>(num_samples);
return true;
}
void QualityScaler::MovingAverage::Reset() {
sum_ = 0;
samples_.clear();
}
void QualityScaler::ClearSamples() {
average_qp_.Reset();
framedrop_percent_.Reset();
}
void QualityScaler::AdjustScale(bool up) {
downscale_shift_ += up ? -1 : 1;
if (downscale_shift_ < 0)
downscale_shift_ = 0;
ClearSamples();
}
} // namespace webrtc
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