Add framerate to VideoSinkWants and ability to signal on overuse

webrtc/media/engine/webrtcvideoengine2.cc

Index: webrtc/media/engine/webrtcvideoengine2.cc
diff --git a/webrtc/media/engine/webrtcvideoengine2.cc b/webrtc/media/engine/webrtcvideoengine2.cc
index 8b4c5df1814601757b5d74b80eccf9087c745be5..1bc93ef24a0c3a66110e1a2ed4998109c01f2a95 100644
--- a/webrtc/media/engine/webrtcvideoengine2.cc
+++ b/webrtc/media/engine/webrtcvideoengine2.cc
@@ -38,9 +38,10 @@
 #include "webrtc/video_decoder.h"
 #include "webrtc/video_encoder.h"
 
+using DegradationPreference = webrtc::VideoSendStream::DegradationPreference;

[nisse-webrtc, 2017/03/14 09:00:29]

Perhaps not for this cl, but if DegradationPreference is intended as a public
high-level API, it should perhaps be in the top-level webrtc namespace.

[sprang_webrtc, 2017/03/14 14:15:02]

Agreed. I think we need to overhaul a few pieces of our api's. But that usually
get's messy, so let's do it in something smaller and more easily revertable :)

+
 namespace cricket {
 namespace {
-
 // If this field trial is enabled, we will enable sending FlexFEC and disable
 // sending ULPFEC whenever the former has been negotiated. Receiving FlexFEC
 // is enabled whenever FlexFEC has been negotiated.
@@ -1627,7 +1628,8 @@ bool WebRtcVideoChannel2::WebRtcVideoSendStream::SetVideoSend(
 
   if (source_ && stream_) {
     stream_->SetSource(
-        nullptr, webrtc::VideoSendStream::DegradationPreference::kBalanced);
+        nullptr,
+        webrtc::VideoSendStream::DegradationPreference::kDegradationDisabled);

[kthelgason, 2017/03/14 10:01:20]

just DegradationPreference::kDegradationDisabled given the using directive
above.

[sprang_webrtc, 2017/03/14 14:15:02]

Done.

   }
   // Switch to the new source.
   source_ = source;
@@ -1636,12 +1638,17 @@ bool WebRtcVideoChannel2::WebRtcVideoSendStream::SetVideoSend(
     // result in blurry and unreadable text.
     // |this| acts like a VideoSource to make sure SinkWants are handled on the
     // correct thread.
-    stream_->SetSource(
-        this, enable_cpu_overuse_detection_ &&
-                      !parameters_.options.is_screencast.value_or(false)
-                  ? webrtc::VideoSendStream::DegradationPreference::kBalanced
-                  : webrtc::VideoSendStream::DegradationPreference::
-                        kMaintainResolution);
+    DegradationPreference degradation_preference;
+    if (!enable_cpu_overuse_detection_) {
+      degradation_preference = DegradationPreference::kDegradationDisabled;

[nisse-webrtc, 2017/03/14 09:00:29]

I wonder if this disable value should be made available to applications, all the
way up to js? I don't think the name is quite right in that context. 

[sprang_webrtc, 2017/03/14 14:15:02]

|enable_cpu_overuse_detection_| is currently populated from js as a media
constraint I believe. I'm just making a simple translation here. For ortc I
guess we wan't to just use degradation preference, right?

+    } else {
+      if (parameters_.options.is_screencast.value_or(false)) {
+        degradation_preference = DegradationPreference::kMaintainResolution;
+      } else {
+        degradation_preference = DegradationPreference::kMaintainFramerate;
+      }
+    }
+    stream_->SetSource(this, degradation_preference);
   }
   return true;
 }
@@ -2088,11 +2095,12 @@ void WebRtcVideoChannel2::WebRtcVideoSendStream::RecreateWebRtcStream() {
     // |this| acts like a VideoSource to make sure SinkWants are handled on the
     // correct thread.
     stream_->SetSource(
-        this, enable_cpu_overuse_detection_ &&
-                      !parameters_.options.is_screencast.value_or(false)
-                  ? webrtc::VideoSendStream::DegradationPreference::kBalanced
-                  : webrtc::VideoSendStream::DegradationPreference::
-                        kMaintainResolution);
+        this,
+        enable_cpu_overuse_detection_ &&
+                !parameters_.options.is_screencast.value_or(false)
+            ? webrtc::VideoSendStream::DegradationPreference::kMaintainFramerate

[nisse-webrtc, 2017/03/14 09:00:29]

Why is this logic different from logic in SetVideoSend, above?

It would be clearer if the logic were the same, and common code extracted to a
helper method.

[sprang_webrtc, 2017/03/14 14:15:02]

Done.

+            : webrtc::VideoSendStream::DegradationPreference::
+                  kMaintainResolution);
   }
 
   // Call stream_->Start() if necessary conditions are met.