Move the QP scaling thresholds to the relevant encoders.

Also provide a new set of thresholds for the VideoToolbox encoder. The new thresholds were experimentally determined to work well on the iPhone 6S, and also adequately on the iPhone 5S.

BUG=webrtc:5678

Review-Url: https://codereview.webrtc.org/2309743002
Cr-Commit-Position: refs/heads/master@{#14420}

webrtc/api/android/jni/androidmediaencoder_jni.cc

@@ -395,16 +395,9 @@ int32_t MediaCodecVideoEncoder::InitEncode(
   ALOGD << "Encoder automatic resize " << (scale_ ? "enabled" : "disabled");
 
   if (scale_) {
-    if (codecType_ == kVideoCodecVP8) {
+    if (codecType_ == kVideoCodecVP8 || codecType_ == kVideoCodecH264) {
-      quality_scaler_.Init(
+      quality_scaler_.Init(codecType_, codec_settings->startBitrate,
-          QualityScaler::kLowVp8QpThreshold, QualityScaler::kBadVp8QpThreshold,
+                           codec_settings->width, codec_settings->height,
-          codec_settings->startBitrate, codec_settings->width,
-          codec_settings->height, codec_settings->maxFramerate);
-    } else if (codecType_ == kVideoCodecH264) {
-      quality_scaler_.Init(QualityScaler::kLowH264QpThreshold,
-                           QualityScaler::kBadH264QpThreshold,
-                           codec_settings->startBitrate, codec_settings->width,
-                           codec_settings->height,
                            codec_settings->maxFramerate);
     } else {
       // When adding codec support to additional hardware codecs, also configure

webrtc/modules/video_coding/codecs/h264/h264_encoder_impl.cc

@@ -213,10 +213,9 @@ int32_t H264EncoderImpl::InitEncode(const VideoCodec* codec_settings,
     return WEBRTC_VIDEO_CODEC_ERROR;
   }
   // TODO(pbos): Base init params on these values before submitting.
-  quality_scaler_.Init(QualityScaler::kLowH264QpThreshold,
+  quality_scaler_.Init(codec_settings_.codecType, codec_settings_.startBitrate,
-                       QualityScaler::kBadH264QpThreshold,
+                       codec_settings_.width, codec_settings_.height,
-                       codec_settings_.startBitrate, codec_settings_.width,
+                       codec_settings_.maxFramerate);
-                       codec_settings_.height, codec_settings_.maxFramerate);
   int video_format = EVideoFormatType::videoFormatI420;
   openh264_encoder_->SetOption(ENCODER_OPTION_DATAFORMAT,
                                &video_format);

webrtc/modules/video_coding/codecs/h264/h264_video_toolbox_encoder.mm

@@ -33,6 +33,10 @@ namespace internal {
 // kVTCompressionPropertyKey_AverageBitRate. The data rate limit is set higher
 // than the average bit rate to avoid undershooting the target.
 const float kLimitToAverageBitRateFactor = 1.5f;
+// These thresholds deviate from the default h264 QP thresholds, as they
+// have been found to work better on devices that support VideoToolbox
+const int kLowH264QpThreshold = 28;
+const int kHighH264QpThreshold = 39;
 
 // Convenience function for creating a dictionary.
 inline CFDictionaryRef CreateCFDictionary(CFTypeRef* keys,
@@ -232,8 +236,8 @@ int H264VideoToolboxEncoder::InitEncode(const VideoCodec* codec_settings,
   RTC_DCHECK_EQ(codec_settings->codecType, kVideoCodecH264);
   {
     rtc::CritScope lock(&quality_scaler_crit_);
-    quality_scaler_.Init(QualityScaler::kLowH264QpThreshold,
+    quality_scaler_.Init(internal::kLowH264QpThreshold,
-                         QualityScaler::kBadH264QpThreshold,
+                         internal::kHighH264QpThreshold,
                          codec_settings->startBitrate, codec_settings->width,
                          codec_settings->height, codec_settings->maxFramerate);
     QualityScaler::Resolution res = quality_scaler_.GetScaledResolution();

webrtc/modules/video_coding/codecs/vp8/vp8_impl.cc

@@ -562,9 +562,8 @@ int VP8EncoderImpl::InitEncode(const VideoCodec* inst,
   }
 
   rps_.Init();
-  quality_scaler_.Init(QualityScaler::kLowVp8QpThreshold,
+  quality_scaler_.Init(codec_.codecType, codec_.startBitrate, codec_.width,
-                       QualityScaler::kBadVp8QpThreshold, codec_.startBitrate,
+                       codec_.height, codec_.maxFramerate);
-                       codec_.width, codec_.height, codec_.maxFramerate);
 
   // Only apply scaling to improve for single-layer streams. The scaling metrics
   // use frame drops as a signal and is only applicable when we drop frames.

webrtc/modules/video_coding/utility/quality_scaler.cc

@@ -14,6 +14,8 @@
 
 #include <algorithm>
 
+#include "webrtc/base/checks.h"
+
 // TODO(kthelgason): Some versions of Android have issues with log2.
 // See https://code.google.com/p/android/issues/detail?id=212634 for details
 #if defined(WEBRTC_ANDROID)
@@ -38,42 +40,54 @@ static const int kVgaBitrateThresholdKbps = 500;
 static const int kVgaNumPixels = 700 * 500;  // 640x480
 static const int kQvgaBitrateThresholdKbps = 250;
 static const int kQvgaNumPixels = 400 * 300;  // 320x240
+
+// QP scaling threshold defaults:
+static const int kLowH264QpThreshold = 24;
+static const int kHighH264QpThreshold = 37;
+// QP is obtained from VP8-bitstream for HW, so the QP corresponds to the
+// bitstream range of [0, 127] and not the user-level range of [0,63].
+static const int kLowVp8QpThreshold = 29;
+static const int kHighVp8QpThreshold = 95;
 }  // 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 = 95;
-
-#if defined(WEBRTC_IOS)
-const int QualityScaler::kLowH264QpThreshold = 32;
-const int QualityScaler::kBadH264QpThreshold = 42;
-#else
-const int QualityScaler::kLowH264QpThreshold = 24;
-const int QualityScaler::kBadH264QpThreshold = 37;
-#endif
-
 // Default values. Should immediately get set to something more sensible.
 QualityScaler::QualityScaler()
     : average_qp_(kMeasureSecondsUpscale * 30),
       framedrop_percent_(kMeasureSecondsUpscale * 30),
       low_qp_threshold_(-1) {}
 
+void QualityScaler::Init(VideoCodecType codec_type,
+                         int initial_bitrate_kbps,
+                         int width,
+                         int height,
+                         int fps) {
+  int low = -1, high = -1;
+  switch (codec_type) {
+    case kVideoCodecH264:
+      low = kLowH264QpThreshold;
+      high = kHighH264QpThreshold;
+      break;
+    case kVideoCodecVP8:
+      low = kLowVp8QpThreshold;
+      high = kHighVp8QpThreshold;
+      break;
+    default:
+      RTC_NOTREACHED() << "Invalid codec type for QualityScaler.";
+  }
+  Init(low, high, initial_bitrate_kbps, width, height, fps);
+}
+
 void QualityScaler::Init(int low_qp_threshold,
                          int high_qp_threshold,
                          int initial_bitrate_kbps,
                          int width,
                          int height,
                          int fps) {
+  ClearSamples();
   low_qp_threshold_ = low_qp_threshold;
   high_qp_threshold_ = high_qp_threshold;
   downscale_shift_ = 0;
-
   fast_rampup_ = true;
-
-  ClearSamples();
   ReportFramerate(fps);
 
   const int init_width = width;

webrtc/modules/video_coding/utility/quality_scaler.h

@@ -11,6 +11,7 @@
 #ifndef WEBRTC_MODULES_VIDEO_CODING_UTILITY_QUALITY_SCALER_H_
 #define WEBRTC_MODULES_VIDEO_CODING_UTILITY_QUALITY_SCALER_H_
 
+#include "webrtc/common_types.h"
 #include "webrtc/common_video/include/i420_buffer_pool.h"
 #include "webrtc/modules/video_coding/utility/moving_average.h"
 
@@ -23,6 +24,11 @@ class QualityScaler {
   };
 
   QualityScaler();
+  void Init(VideoCodecType codec_type,
+            int initial_bitrate_kbps,
+            int width,
+            int height,
+            int fps);
   void Init(int low_qp_threshold,
             int high_qp_threshold,
             int initial_bitrate_kbps,
@@ -38,15 +44,6 @@ class QualityScaler {
       const rtc::scoped_refptr<VideoFrameBuffer>& frame);
   int downscale_shift() const { return downscale_shift_; }
 
-  // QP is obtained from VP8-bitstream for HW, so the QP corresponds to the
-  // bitstream range of [0, 127] and not the user-level range of [0,63].
-  static const int kLowVp8QpThreshold;
-  static const int kBadVp8QpThreshold;
-
-  // H264 QP is in the range [0, 51].
-  static const int kLowH264QpThreshold;
-  static const int kBadH264QpThreshold;
-
  private:
   void ClearSamples();
   void ScaleUp();