Make QualityScaler not downscale below QVGA.

webrtc/modules/video_coding/utility/quality_scaler.cc

Index: webrtc/modules/video_coding/utility/quality_scaler.cc
diff --git a/webrtc/modules/video_coding/utility/quality_scaler.cc b/webrtc/modules/video_coding/utility/quality_scaler.cc
index c6e566973101e01f1ec868f8810e614d7a3480e7..1f2a7c387316593150623a9c2de30c4e59f8044f 100644
--- a/webrtc/modules/video_coding/utility/quality_scaler.cc
+++ b/webrtc/modules/video_coding/utility/quality_scaler.cc
@@ -20,16 +20,14 @@ static const int kFramedropPercentThreshold = 60;
 static const int kHdResolutionThreshold = 700 * 500;
 static const int kHdBitrateThresholdKbps = 500;
 
+// Min width/height to downscale to, set to not go below QVGA, but with some
+// margin to permit "almost-QVGA" resolutions.
+static const int kMinDownscaleDimension = 160;

[danilchap, 2016/04/14 09:27:36]

May be put kMinDownscaleDimension into the QualityScale class instead of webrtc
namespace.
This way
 there will be no need to redeclare this value in unittests;
 would give code reader hint QualityScaler still has min resolution, it just
can't be set any more.

[pbos-webrtc, 2016/04/14 12:13:16]

I'll keep it this way for now, since we have more corresponding values that
could be considered separately. Putting them under an anonymous namespace though
for now.

+
 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()
-    : low_qp_threshold_(-1),
-      framerate_down_(false),
-      min_width_(kDefaultMinDownscaleDimension),
-      min_height_(kDefaultMinDownscaleDimension) {}
+    : low_qp_threshold_(-1), framerate_down_(false) {}
 
 void QualityScaler::Init(int low_qp_threshold,
                          int high_qp_threshold,
@@ -65,11 +63,6 @@ void QualityScaler::Init(int low_qp_threshold,
   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) {
   framerate_ = framerate;
@@ -158,8 +151,8 @@ void QualityScaler::UpdateTargetResolution(int frame_width, int frame_height) {
   res_.width = frame_width;
   res_.height = frame_height;
   for (int shift = downscale_shift_;
-       shift > 0 && (res_.width / 2 >= min_width_) &&
-       (res_.height / 2 >= min_height_);
+       shift > 0 && (res_.width / 2 >= kMinDownscaleDimension) &&
+       (res_.height / 2 >= kMinDownscaleDimension);
        --shift) {
     res_.width /= 2;
     res_.height /= 2;