Implement new specification for degradation preference

The degradation preference is now based on the content hint of the track
if it's unspecified.

Bug: webrtc:11164
Change-Id: Iaa0dbf1c1bf68a46fc5131e534d423c30c5439c7
Reviewed-on: https://webrtc-review.googlesource.com/c/src/+/161233
Commit-Queue: Florent Castelli <orphis@webrtc.org>
Reviewed-by: Stefan Holmer <stefan@webrtc.org>
Reviewed-by: Ilya Nikolaevskiy <ilnik@webrtc.org>
Reviewed-by: Åsa Persson <asapersson@webrtc.org>
Cr-Commit-Position: refs/heads/master@{#30691}

5 files changed, 35 insertions, 19 deletions

diff --git a/media/BUILD.gn b/media/BUILD.gn
index f68f9911f3..8c2d8c0d0c 100644
--- a/media/BUILD.gn
+++ b/media/BUILD.gn
@@ -280,6 +280,7 @@ rtc_library("rtc_audio_video") {
     "..:webrtc_common",
     "../api:call_api",
     "../api:libjingle_peerconnection_api",
+    "../api:media_stream_interface",
     "../api:rtp_parameters",
     "../api:scoped_refptr",
     "../api:transport_api",
diff --git a/media/base/media_channel.cc b/media/base/media_channel.cc
index 3417924730..2e9bfc3d31 100644
--- a/media/base/media_channel.cc
+++ b/media/base/media_channel.cc
@@ -12,7 +12,8 @@
 
 namespace cricket {
 
-VideoOptions::VideoOptions() = default;
+VideoOptions::VideoOptions()
+    : content_hint(webrtc::VideoTrackInterface::ContentHint::kNone) {}
 VideoOptions::~VideoOptions() = default;
 
 MediaChannel::MediaChannel(const MediaConfig& config)
diff --git a/media/base/media_channel.h b/media/base/media_channel.h
index 8ee4a238a1..a62c618562 100644
--- a/media/base/media_channel.h
+++ b/media/base/media_channel.h
@@ -23,6 +23,7 @@
 #include "api/crypto/frame_decryptor_interface.h"
 #include "api/crypto/frame_encryptor_interface.h"
 #include "api/frame_transformer_interface.h"
+#include "api/media_stream_interface.h"
 #include "api/rtc_error.h"
 #include "api/rtp_parameters.h"
 #include "api/transport/media/media_transport_config.h"
@@ -144,6 +145,7 @@ struct VideoOptions {
   // things, e.g., screencast of a text document and screencast of a
   // youtube video have different needs.
   absl::optional<bool> is_screencast;
+  webrtc::VideoTrackInterface::ContentHint content_hint;
 
  private:
   template <typename T>
diff --git a/media/engine/webrtc_video_engine.cc b/media/engine/webrtc_video_engine.cc
index b2f842950e..48aea63cf8 100644
--- a/media/engine/webrtc_video_engine.cc
+++ b/media/engine/webrtc_video_engine.cc
@@ -19,6 +19,7 @@
 
 #include "absl/algorithm/container.h"
 #include "absl/strings/match.h"
+#include "api/media_stream_interface.h"
 #include "api/transport/datagram_transport_interface.h"
 #include "api/units/data_rate.h"
 #include "api/video/video_codec_constants.h"
@@ -1948,25 +1949,37 @@ WebRtcVideoChannel::WebRtcVideoSendStream::GetDegradationPreference() const {
   // result in blurry and unreadable text.
   // |this| acts like a VideoSource to make sure SinkWants are handled on the
   // correct thread.
+  if (!enable_cpu_overuse_detection_) {
+    return webrtc::DegradationPreference::DISABLED;
+  }
+
   webrtc::DegradationPreference degradation_preference;
-  if (rtp_parameters_.degradation_preference !=
-      webrtc::DegradationPreference::BALANCED) {
-    // If the degradationPreference is different from the default value, assume
-    // it is what we want, regardless of trials or other internal settings.
-    degradation_preference = rtp_parameters_.degradation_preference;
-  } else if (!enable_cpu_overuse_detection_) {
-    degradation_preference = webrtc::DegradationPreference::DISABLED;
-  } else if (parameters_.options.is_screencast.value_or(false)) {
-    degradation_preference = webrtc::DegradationPreference::MAINTAIN_RESOLUTION;
-  } else if (webrtc::field_trial::IsEnabled(
-                 "WebRTC-Video-BalancedDegradation")) {
-    degradation_preference = webrtc::DegradationPreference::BALANCED;
+  if (rtp_parameters_.degradation_preference.has_value()) {
+    degradation_preference = *rtp_parameters_.degradation_preference;
   } else {
-    // TODO(orphis): The default should be BALANCED as the standard mandates.
-    // Right now, there is no way to set it to BALANCED as it would change
-    // the behavior for any project expecting MAINTAIN_FRAMERATE by default.
-    degradation_preference = webrtc::DegradationPreference::MAINTAIN_FRAMERATE;
+    if (parameters_.options.content_hint ==
+        webrtc::VideoTrackInterface::ContentHint::kFluid) {
+      degradation_preference =
+          webrtc::DegradationPreference::MAINTAIN_FRAMERATE;
+    } else if (parameters_.options.is_screencast.value_or(false) ||
+               parameters_.options.content_hint ==
+                   webrtc::VideoTrackInterface::ContentHint::kDetailed ||
+               parameters_.options.content_hint ==
+                   webrtc::VideoTrackInterface::ContentHint::kText) {
+      degradation_preference =
+          webrtc::DegradationPreference::MAINTAIN_RESOLUTION;
+    } else if (webrtc::field_trial::IsEnabled(
+                   "WebRTC-Video-BalancedDegradation")) {
+      // Standard wants balanced by default, but it needs to be tuned first.
+      degradation_preference = webrtc::DegradationPreference::BALANCED;
+    } else {
+      // Keep MAINTAIN_FRAMERATE by default until BALANCED has been tuned for
+      // all codecs and launched.
+      degradation_preference =
+          webrtc::DegradationPreference::MAINTAIN_FRAMERATE;
+    }
   }
+
   return degradation_preference;
 }
 
diff --git a/media/engine/webrtc_video_engine_unittest.cc b/media/engine/webrtc_video_engine_unittest.cc
index d294d3153b..d33a2c3532 100644
--- a/media/engine/webrtc_video_engine_unittest.cc
+++ b/media/engine/webrtc_video_engine_unittest.cc
@@ -7318,8 +7318,7 @@ TEST_F(WebRtcVideoChannelTest, GetRtpSendParametersDegradationPreference) {
 
   webrtc::RtpParameters rtp_parameters =
       channel_->GetRtpSendParameters(last_ssrc_);
-  EXPECT_EQ(rtp_parameters.degradation_preference,
-            webrtc::DegradationPreference::BALANCED);
+  EXPECT_FALSE(rtp_parameters.degradation_preference.has_value());
   rtp_parameters.degradation_preference =
       webrtc::DegradationPreference::MAINTAIN_FRAMERATE;