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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/include/quality_scaler.h"
namespace webrtc {
static const int kMinFps = 10;
static const int kMeasureSeconds = 5;
static const int kFramedropPercentThreshold = 60;
const int QualityScaler::kDefaultLowQpDenominator = 3;
// Note that this is the same for width and height to permit 120x90 in both
// portrait and landscape mode.
const int QualityScaler::kDefaultMinDownscaleDimension = 90;
QualityScaler::QualityScaler()
: num_samples_(0),
low_qp_threshold_(-1),
downscale_shift_(0),
framerate_down_(false),
min_width_(kDefaultMinDownscaleDimension),
min_height_(kDefaultMinDownscaleDimension) {
}
void QualityScaler::Init(int low_qp_threshold,
int high_qp_threshold,
bool use_framerate_reduction) {
ClearSamples();
low_qp_threshold_ = low_qp_threshold;
high_qp_threshold_ = high_qp_threshold;
use_framerate_reduction_ = use_framerate_reduction;
target_framerate_ = -1;
}
void QualityScaler::SetMinResolution(int min_width, int min_height) {
min_width_ = min_width;
min_height_ = min_height;
}
// Report framerate(fps) to estimate # of samples.
void QualityScaler::ReportFramerate(int framerate) {
num_samples_ = static_cast<size_t>(
kMeasureSeconds * (framerate < kMinFps ? kMinFps : framerate));
framerate_ = framerate;
}
void QualityScaler::ReportQP(int qp) {
framedrop_percent_.AddSample(0);
average_qp_.AddSample(qp);
}
void QualityScaler::ReportDroppedFrame() {
framedrop_percent_.AddSample(100);
}
void QualityScaler::OnEncodeFrame(const VideoFrame& frame) {
// Should be set through InitEncode -> Should be set by now.
assert(low_qp_threshold_ >= 0);
assert(num_samples_ > 0);
res_.width = frame.width();
res_.height = frame.height();
// Update scale factor.
int avg_drop = 0;
int avg_qp = 0;
// When encoder consistently overshoots, framerate reduction and spatial
// resizing will be triggered to get a smoother video.
if ((framedrop_percent_.GetAverage(num_samples_, &avg_drop) &&
avg_drop >= kFramedropPercentThreshold) ||
(average_qp_.GetAverage(num_samples_, &avg_qp) &&
avg_qp > high_qp_threshold_)) {
// Reducing frame rate before spatial resolution change.
// Reduce frame rate only when it is above a certain number.
// Only one reduction is allowed for now.
// TODO(jackychen): Allow more than one framerate reduction.
if (use_framerate_reduction_ && !framerate_down_ && framerate_ >= 20) {
target_framerate_ = framerate_ / 2;
framerate_down_ = true;
// If frame rate has been updated, clear the buffer. We don't want
// spatial resolution to change right after frame rate change.
ClearSamples();
} else {
AdjustScale(false);
}
} else if (average_qp_.GetAverage(num_samples_, &avg_qp) &&
avg_qp <= low_qp_threshold_) {
if (use_framerate_reduction_ && framerate_down_) {
target_framerate_ = -1;
framerate_down_ = false;
ClearSamples();
} else {
AdjustScale(true);
}
}
assert(downscale_shift_ >= 0);
for (int shift = downscale_shift_;
shift > 0 && (res_.width / 2 >= min_width_) &&
(res_.height / 2 >= min_height_);
--shift) {
res_.width /= 2;
res_.height /= 2;
}
}
QualityScaler::Resolution QualityScaler::GetScaledResolution() const {
return res_;
}
int QualityScaler::GetTargetFramerate() const {
return target_framerate_;
}
const VideoFrame& QualityScaler::GetScaledFrame(const VideoFrame& frame) {
Resolution res = GetScaledResolution();
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_;
}
void QualityScaler::ClearSamples() {
framedrop_percent_.Reset();
average_qp_.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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