Update sink wants with ranges for both pixel count and frame rate.

webrtc/video/vie_encoder.cc

Index: webrtc/video/vie_encoder.cc
diff --git a/webrtc/video/vie_encoder.cc b/webrtc/video/vie_encoder.cc
index 1458af266f68efb6692756205f2296b6cd217e20..995af4dd099613864a814e625f6b0515ab62d27f 100644
--- a/webrtc/video/vie_encoder.cc
+++ b/webrtc/video/vie_encoder.cc
@@ -163,9 +163,21 @@ class ViEEncoder::VideoSourceProxy {
     {
       rtc::CritScope lock(&crit_);
       old_source = source_;
-      source_ = source;
+      wants = sink_wants_;
+      // If changing degradation preference, clear any constraints from the
+      // current sink wants that will no longer apply.
+      if (degradation_preference_ != degradation_preference) {
+        switch (degradation_preference) {
+          case DegradationPreference::kBalanced:
+            wants.framerate_fps_.reset();
+            break;
+          case DegradationPreference::kMaintainResolution:
+            wants.pixel_count.reset();
+            break;
+        }
+      }
       degradation_preference_ = degradation_preference;
-      wants = current_wants();
+      source_ = source;
     }
 
     if (old_source != source && old_source != nullptr) {
@@ -182,9 +194,8 @@ class ViEEncoder::VideoSourceProxy {
   void SetWantsRotationApplied(bool rotation_applied) {
     rtc::CritScope lock(&crit_);
     sink_wants_.rotation_applied = rotation_applied;
-    disabled_scaling_sink_wants_.rotation_applied = rotation_applied;
     if (source_) {
-      source_->AddOrUpdateSink(vie_encoder_, current_wants());
+      source_->AddOrUpdateSink(vie_encoder_, sink_wants_);
     }
   }
 
@@ -203,12 +214,16 @@ class ViEEncoder::VideoSourceProxy {
     const int pixels_wanted = (pixel_count * 3) / 5;
     if (pixels_wanted < kMinPixelsPerFrame)
       return;
-    sink_wants_.max_pixel_count = rtc::Optional<int>(pixels_wanted);
-    sink_wants_.target_pixel_count = rtc::Optional<int>();
+    sink_wants_.pixel_count.emplace(rtc::VideoSinkWants::Range(
+        kMinPixelsPerFrame, pixels_wanted, pixel_count - 1));
     if (source_)
       source_->AddOrUpdateSink(vie_encoder_, sink_wants_);
   }
 
+  void RequestFramerateLowerThan(int framerate_fps) {
+    // TODO(sprang): Update SinkWants.
+  }
+
   void RequestHigherResolutionThan(int pixel_count) {
     rtc::CritScope lock(&crit_);
     if (!IsResolutionScalingEnabledLocked()) {
@@ -217,18 +232,21 @@ class ViEEncoder::VideoSourceProxy {
       // task queue.
       return;
     }
-    // On step down we request at most 3/5 the pixel count of the previous
-    // resolution, so in order to take "one step up" we request a resolution as
-    // close as possible to 5/3 of the current resolution. The actual pixel
-    // count selected depends on the capabilities of the source. In order to not
-    // take a too large step up, we cap the requested pixel count to be at most
-    // four time the current number of pixels.
-    sink_wants_.target_pixel_count = rtc::Optional<int>((pixel_count * 5) / 3);
-    sink_wants_.max_pixel_count = rtc::Optional<int>(pixel_count * 4);
+
+    // The input video frame size will have a resolution with "one step up"
+    // pixels than |max_pixel_count_step_up| where "one step up" depends on
+    // how the source can scale the input frame size. We still cap the step up
+    // to be at most twice the number of pixels.
+    sink_wants_.pixel_count.emplace(rtc::VideoSinkWants::Range(
+        pixel_count + 1, (pixel_count * 5) / 3, pixel_count * 4));
     if (source_)
       source_->AddOrUpdateSink(vie_encoder_, sink_wants_);
   }
 
+  void RequestHigherFramerateThan(int framerate_fps) {
+    // TODO(sprang): Update SinkWants.
+  }
+
  private:
   bool IsResolutionScalingEnabledLocked() const
       EXCLUSIVE_LOCKS_REQUIRED(&crit_) {
@@ -236,17 +254,16 @@ class ViEEncoder::VideoSourceProxy {
            DegradationPreference::kMaintainResolution;
   }
 
-  const rtc::VideoSinkWants& current_wants() const
+  bool IsFramerateScalingEnabledLocked() const
       EXCLUSIVE_LOCKS_REQUIRED(&crit_) {
-    return IsResolutionScalingEnabledLocked() ? sink_wants_
-                                              : disabled_scaling_sink_wants_;
+    return degradation_preference_ ==
+           DegradationPreference::kMaintainResolution;
   }
 
   rtc::CriticalSection crit_;
   rtc::SequencedTaskChecker main_checker_;
   ViEEncoder* const vie_encoder_;
   rtc::VideoSinkWants sink_wants_ GUARDED_BY(&crit_);
-  rtc::VideoSinkWants disabled_scaling_sink_wants_ GUARDED_BY(&crit_);
   DegradationPreference degradation_preference_ GUARDED_BY(&crit_);
   rtc::VideoSourceInterface<VideoFrame>* source_ GUARDED_BY(&crit_);
 
@@ -741,19 +758,37 @@ void ViEEncoder::OnBitrateUpdated(uint32_t bitrate_bps,
 
 void ViEEncoder::AdaptDown(AdaptReason reason) {
   RTC_DCHECK_RUN_ON(&encoder_queue_);
-  if (degradation_preference_ != DegradationPreference::kBalanced)
-    return;
-  RTC_DCHECK(static_cast<bool>(last_frame_info_));
-  int current_pixel_count = last_frame_info_->pixel_count();
+  AdaptationRequest adaptation_request = {
+      last_frame_info_->pixel_count(),
+      stats_proxy_->GetStats().input_frame_rate,
+      AdaptationRequest::Mode::kAdaptDown};
+
   if (last_adaptation_request_ &&
-      last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptDown &&
-      current_pixel_count >= last_adaptation_request_->input_pixel_count_) {
-    // Don't request lower resolution if the current resolution is not lower
-    // than the last time we asked for the resolution to be lowered.
-    return;
+      last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptDown) {
+    switch (degradation_preference_) {
+      case DegradationPreference::kBalanced:
+        if (adaptation_request.input_pixel_count_ >=
+            last_adaptation_request_->input_pixel_count_) {
+          // Don't request lower resolution if the current resolution is not
+          // lower
+          // than the last time we asked for the resolution to be lowered.
+          return;
+        }
+        break;
+      case DegradationPreference::kMaintainResolution:
+        if (adaptation_request.framerate_fps_ <= 1) {
+          // Don't request lower framerate if we don't have a valid frame rate.
+          // Since framerate, unlike resolution, is a measure we have to
+          // estimate, and can fluctuate naturally over time, don't make the
+          // same kind of limitations as for resolution, but trust the overuse
+          // detector to not trigger too often.
+          return;
+        }
+        break;
+    }
   }
-  last_adaptation_request_.emplace(AdaptationRequest{
-      current_pixel_count, AdaptationRequest::Mode::kAdaptDown});
+
+  last_adaptation_request_.emplace(adaptation_request);
 
   switch (reason) {
     case kQuality:
@@ -768,8 +803,20 @@ void ViEEncoder::AdaptDown(AdaptReason reason) {
       break;
   }
   ++scale_counter_[reason];
-  source_proxy_->RequestResolutionLowerThan(current_pixel_count);
-  LOG(LS_INFO) << "Scaling down resolution.";
+
+  switch (degradation_preference_) {
+    case DegradationPreference::kBalanced:
+      source_proxy_->RequestResolutionLowerThan(
+          adaptation_request.input_pixel_count_);
+      LOG(LS_INFO) << "Scaling down resolution.";
+      break;
+    case DegradationPreference::kMaintainResolution:
+      source_proxy_->RequestFramerateLowerThan(
+          adaptation_request.framerate_fps_);
+      LOG(LS_INFO) << "Scaling down framerate.";
+      break;
+  }
+
   for (size_t i = 0; i < kScaleReasonSize; ++i) {
     LOG(LS_INFO) << "Scaled " << scale_counter_[i]
                  << " times for reason: " << (i ? "cpu" : "quality");
@@ -782,19 +829,31 @@ void ViEEncoder::AdaptUp(AdaptReason reason) {
       degradation_preference_ != DegradationPreference::kBalanced) {
     return;
   }
-  // Only scale if resolution is higher than last time we requested higher
-  // resolution.
-  RTC_DCHECK(static_cast<bool>(last_frame_info_));
-  int current_pixel_count = last_frame_info_->pixel_count();
+
+  AdaptationRequest adaptation_request = {
+      last_frame_info_->pixel_count(),
+      stats_proxy_->GetStats().input_frame_rate,
+      AdaptationRequest::Mode::kAdaptUp};
+
   if (last_adaptation_request_ &&
-      last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptUp &&
-      current_pixel_count <= last_adaptation_request_->input_pixel_count_) {
-    // Don't request higher resolution if the current resolution is not higher
-    // than the last time we asked for the resolution to be higher.
-    return;
+      last_adaptation_request_->mode_ == AdaptationRequest::Mode::kAdaptUp) {
+    switch (degradation_preference_) {
+      case DegradationPreference::kBalanced:
+        if (adaptation_request.input_pixel_count_ <=
+            last_adaptation_request_->input_pixel_count_) {
+          // Don't request higher resolution if the current resolution is not
+          // higher than the last time we asked for the resolution to be higher.
+          return;
+        }
+        break;
+      case DegradationPreference::kMaintainResolution:
+        // TODO(sprang): Don't request higher framerate if we are already at
+        // max requested fps?
+        break;
+    }
   }
-  last_adaptation_request_.emplace(AdaptationRequest{
-      current_pixel_count, AdaptationRequest::Mode::kAdaptUp});
+
+  last_adaptation_request_.emplace(adaptation_request);
 
   switch (reason) {
     case kQuality:
@@ -808,8 +867,20 @@ void ViEEncoder::AdaptUp(AdaptReason reason) {
       break;
   }
   --scale_counter_[reason];
-  source_proxy_->RequestHigherResolutionThan(current_pixel_count);
-  LOG(LS_INFO) << "Scaling up resolution.";
+
+  switch (degradation_preference_) {
+    case DegradationPreference::kBalanced:
+      source_proxy_->RequestHigherResolutionThan(
+          adaptation_request.input_pixel_count_);
+      LOG(LS_INFO) << "Scaling up resolution.";
+      break;
+    case DegradationPreference::kMaintainResolution:
+      source_proxy_->RequestHigherFramerateThan(
+          adaptation_request.framerate_fps_);
+      LOG(LS_INFO) << "Scaling up framerate.";
+      break;
+  }
+
   for (size_t i = 0; i < kScaleReasonSize; ++i) {
     LOG(LS_INFO) << "Scaled " << scale_counter_[i]
                  << " times for reason: " << (i ? "cpu" : "quality");