Add support for a command line switch: agc-startup-min-volume

This allows Chrome to be started with a value that overrides the default
starting volume value of WebRTCs Automatic Gain Control algorithm.
Some input devices have a gain input curve that doesn't agree with
the default starting value, so this switch is a useful tool to
test valid values as well as a way to work around configuration
(possibly hardware or driver related) issues in fixed setups.

BUG=555104,555577
R=avi@chromium.org, henrika@chromium.org

Review URL: https://codereview.chromium.org/1440083002 .

Cr-Commit-Position: refs/heads/master@{#359619}

1 files changed, 22 insertions, 0 deletions

diff --git a/content/renderer/media/media_stream_audio_processor.cc b/content/renderer/media/media_stream_audio_processor.cc
index c736696..5e4c1c0 100644
--- a/content/renderer/media/media_stream_audio_processor.cc
+++ b/content/renderer/media/media_stream_audio_processor.cc
@@ -7,6 +7,7 @@
 #include "base/command_line.h"
 #include "base/metrics/field_trial.h"
 #include "base/metrics/histogram.h"
+#include "base/strings/string_number_conversions.h"
 #include "base/trace_event/trace_event.h"
 #include "content/public/common/content_switches.h"
 #include "content/renderer/media/media_stream_audio_processor_options.h"
@@ -107,6 +108,17 @@ bool IsDelayAgnosticAecEnabled() {
   return (group_name == "Enabled" || group_name == "DefaultEnabled");
 }
 
+// Checks if the default minimum starting volume value for the AGC is overridden
+// on the command line.
+bool GetStartupMinVolumeForAgc(int* startup_min_volume) {
+  DCHECK(startup_min_volume);
+  std::string min_volume_str(
+      base::CommandLine::ForCurrentProcess()->GetSwitchValueASCII(
+          switches::kAgcStartupMinVolume));
+  return !min_volume_str.empty() &&
+         base::StringToInt(min_volume_str, startup_min_volume);
+}
+
 }  // namespace
 
 // Wraps AudioBus to provide access to the array of channel pointers, since this
@@ -528,6 +540,16 @@ void MediaStreamAudioProcessor::InitializeAudioProcessingModule(
         new webrtc::Beamforming(geometry.size() > 1, geometry));
   }
 
+  // If the experimental AGC is enabled, check for overridden config params.
+  if (audio_constraints.GetProperty(
+          MediaAudioConstraints::kGoogExperimentalAutoGainControl)) {
+    int startup_min_volume = 0;
+    if (GetStartupMinVolumeForAgc(&startup_min_volume)) {
+      config.Set<webrtc::ExperimentalAgc>(
+          new webrtc::ExperimentalAgc(true, startup_min_volume));
+    }
+  }
+
   // Create and configure the webrtc::AudioProcessing.
   audio_processing_.reset(webrtc::AudioProcessing::Create(config));