Add default downscale threshold to QualityScaler.

webrtc/modules/video_coding/utility/quality_scaler.cc

 /*
  *  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),
-      min_width_(0), min_height_(0) {
+    : num_samples_(0),
+      low_qp_threshold_(-1),
+      downscale_shift_(0),
+      min_width_(kDefaultMinDownscaleDimension),
+      min_height_(kDefaultMinDownscaleDimension) {
 }
 
 void QualityScaler::Init(int low_qp_threshold) {
   ClearSamples();
   low_qp_threshold_ = low_qp_threshold;
 }
 
 void QualityScaler::SetMinResolution(int min_width, int min_height) {
   min_width_ = min_width;
   min_height_ = min_height;
@@ skipping 30 matching lines @@
   if (framedrop_percent_.GetAverage(num_samples_, &avg_drop) &&
       avg_drop >= kFramedropPercentThreshold) {
     AdjustScale(false);
   } else if (average_qp_.GetAverage(num_samples_, &avg_qp) &&
       avg_qp <= low_qp_threshold_) {
     AdjustScale(true);
   }
 
   assert(downscale_shift_ >= 0);
   for (int shift = downscale_shift_;
-       shift > 0 && res.width > 1 && res.height > 1;
+       shift > 0 && (res.width >> 1 >= min_width_) &&
+           (res.height >> 1 >= min_height_);
        --shift) {
     res.width >>= 1;
     res.height >>= 1;
   }
 
-  // Set this limitation for VP8 HW encoder to avoid crash.
-  if (min_width_ > 0 && res.width * res.height < min_width_ * min_height_) {
-    res.width = min_width_;
-    res.height = min_height_;
-  }
-
   return res;
 }
 
 const VideoFrame& QualityScaler::GetScaledFrame(const VideoFrame& frame) {
   Resolution res = GetScaledResolution(frame);
   if (res.width == frame.width())
     return frame;
 
   scaler_.Set(frame.width(),
               frame.height(),
@@ skipping 18 matching lines @@
 }
 
 void QualityScaler::AdjustScale(bool up) {
   downscale_shift_ += up ? -1 : 1;
   if (downscale_shift_ < 0)
     downscale_shift_ = 0;
   ClearSamples();
 }
 
 }  // namespace webrtc