1 files changed, 156 insertions, 0 deletions
diff --git a/webrtc/modules/video_coding/utility/quality_scaler.cc b/webrtc/modules/video_coding/utility/quality_scaler.cc
new file mode 100644
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+++ b/webrtc/modules/video_coding/utility/quality_scaler.cc
@@ -0,0 +1,156 @@
+/*
+ *  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