Unify hardware and software QP thresholds.

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 30a5776b2d05b6d92495e67dfb75743972809854..4c9848ebaea5e1803fb8691aa8b3fd2fe5006812 100644
--- a/webrtc/modules/video_coding/utility/quality_scaler.cc
+++ b/webrtc/modules/video_coding/utility/quality_scaler.cc
@@ -30,6 +30,16 @@ static const int kQvgaBitrateThresholdKbps = 250;
 static const int kQvgaNumPixels = 400 * 300;  // 320x240
 }  // namespace
 
+// QP thresholds are chosen to be high enough to be hit in practice when quality
+// is good, but also low enough to not cause a flip-flop behavior (e.g. going up
+// in resolution shouldn't give so bad quality that we should go back down).
+
+const int QualityScaler::kLowVp8QpThreshold = 29;
+const int QualityScaler::kBadVp8QpThreshold = 100;

[AlexG, 2016/05/11 17:13:48]

I want to keep "bad" threshold at 90 at least for HW codec. 720p encoding may
looks too blocky at QP = 90 and never downscale

[pbos-webrtc, 2016/05/11 17:19:26]

Are you certain that this doesn't flip-flop for either pretty-still video or
when moving around a bit?

+
+const int QualityScaler::kLowH264QpThreshold = 22;
+const int QualityScaler::kBadH264QpThreshold = 35;
+
 QualityScaler::QualityScaler() : low_qp_threshold_(-1) {}
 
 void QualityScaler::Init(int low_qp_threshold,