Add field trial to update quality scaler QP thresholds for Android HW encoder.

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.
  */
 
@@ skipping 94 matching lines @@
       observer_(observer),
       sampling_period_ms_(sampling_period),
       fast_rampup_(true),
       // Arbitrarily choose size based on 30 fps for 5 seconds.
       average_qp_(5 * 30),
       framedrop_percent_(5 * 30),
       thresholds_(thresholds) {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
   RTC_DCHECK(observer_ != nullptr);
   check_qp_task_ = new CheckQPTask(this);
+  LOG(LS_INFO) << "QP thresholds: low: " << thresholds_.low
+               << ", high: " << thresholds_.high;
 }
 
 QualityScaler::~QualityScaler() {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
   check_qp_task_->Stop();
 }
 
 int64_t QualityScaler::GetSamplingPeriodMs() const {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
   return fast_rampup_ ? sampling_period_ms_
@@ skipping 12 matching lines @@
 }
 
 void QualityScaler::CheckQP() {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
   // Should be set through InitEncode -> Should be set by now.
   RTC_DCHECK_GE(thresholds_.low, 0);
   LOG(LS_INFO) << "Checking if average QP exceeds threshold";
   // Check if we should scale down due to high frame drop.
   const rtc::Optional<int> drop_rate = framedrop_percent_.GetAverage();
   if (drop_rate && *drop_rate >= kFramedropPercentThreshold) {
+    LOG(LS_INFO) << "Drop rate " << *drop_rate
+                 << " has been high , asking for lower resolution.";

[kthelgason, 2017/03/22 07:38:58]

There is a bug here (https://bugs.chromium.org/p/webrtc/issues/detail?id=7373)
about reducing the amount of logging done by the quality scaler. Some have
thought it's confusing that it will log even though resolution is at max/min.
Feel free to weigh in on the bug if you feel these log lines are useful.

[AlexG, 2017/03/22 19:53:45]

I am not sure regarding the proper logging here. Probably worth to address in a
separate CL

[stefan-webrtc, 2017/03/23 17:58:04]

I think the current logging is confusing, so I'd probably leave it out if you
don't think it's really necessary. I It will periodically log this (and below)
throughout the call if it can't get a higher/lower resolution

[AlexG, 2017/03/23 19:25:08]

Done. I removed "asking for lower/higher resolution logs". May still worth to
keep QP log to monitor average QP?

     ReportQPHigh();
     return;
   }
 
   // Check if we should scale up or down based on QP.
   const rtc::Optional<int> avg_qp = average_qp_.GetAverage();
   if (avg_qp && *avg_qp > thresholds_.high) {
+    LOG(LS_INFO) << "QP " << *avg_qp
+                 << " has been high , asking for lower resolution.";
     ReportQPHigh();
     return;
   }
   if (avg_qp && *avg_qp <= thresholds_.low) {
     // QP has been low. We want to try a higher resolution.
+    LOG(LS_INFO) << "QP " << *avg_qp
+                 << " has been low, asking for higher resolution.";
     ReportQPLow();
     return;
   }
 }
 
 void QualityScaler::ReportQPLow() {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
-  LOG(LS_INFO) << "QP has been low, asking for higher resolution.";
   ClearSamples();
   observer_->AdaptUp(AdaptationObserverInterface::AdaptReason::kQuality);
 }
 
 void QualityScaler::ReportQPHigh() {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
-  LOG(LS_INFO) << "QP has been high , asking for lower resolution.";
   ClearSamples();
   observer_->AdaptDown(AdaptationObserverInterface::AdaptReason::kQuality);
   // If we've scaled down, wait longer before scaling up again.
   if (fast_rampup_) {
     fast_rampup_ = false;
   }
 }
 
 void QualityScaler::ClearSamples() {
   RTC_DCHECK_CALLED_SEQUENTIALLY(&task_checker_);
   framedrop_percent_.Reset();
   average_qp_.Reset();
 }
 }  // namespace webrtc