Implement a high-QP threshold for Android H.264.

talk/app/webrtc/java/jni/androidmediaencoder_jni.cc

Index: talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
diff --git a/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc b/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
index f6a3b650a6b8aaf481fa941e3bbb777a09dc84b6..f1ef31e21d89b2d741fee3c047c0ea938838e8d5 100644
--- a/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
+++ b/talk/app/webrtc/java/jni/androidmediaencoder_jni.cc
@@ -306,11 +306,18 @@ int32_t MediaCodecVideoEncoder::InitEncode(
       // always = 127. Note that in SW, QP is that of the user-level range [0,
       // 63].
       const int kMaxQp = 127;
-      quality_scaler_.Init(kMaxQp / kLowQpThresholdDenominator, true);
+      // TODO(pbos): Investigate whether high-QP thresholds make sense for VP8.
+      // This effectively disables high QP as VP8 QP can't go above this
+      // threshold.
+      const int kDisabledBadQpThreshold = kMaxQp + 1;
+      quality_scaler_.Init(kMaxQp / kLowQpThresholdDenominator,
+                           kDisabledBadQpThreshold, true);
     } else if (codecType_ == kVideoCodecH264) {
       // H264 QP is in the range [0, 51].
       const int kMaxQp = 51;
-      quality_scaler_.Init(kMaxQp / kLowQpThresholdDenominator, true);
+      const int kBadQpThreshold = 40;
+      quality_scaler_.Init(kMaxQp / kLowQpThresholdDenominator, kBadQpThreshold,
+                           true);

[stefan-webrtc, 2015/09/25 14:18:02]

Maybe we should consider disabling this until we have evaluated if it really
improves quality to drop framerate in half? Mostly to avoid getting stuck at low
framerate and things.

[pbos-webrtc, 2015/09/25 14:24:08]

Done.

     } else {
       // When adding codec support to additional hardware codecs, also configure
       // their QP thresholds for scaling.