Add a noise indicator to the speech bubble volume indicator.

The noise indicator is drawn as a light blue area at the beginning and if there
was clipping that is denoted with a red area at the end of the meter. The noise
level comes from the endpointer -> SpeechRecognizer -> SpeechInputBubbleController -> SpeechInputBubble
hence a bunch of volume setting methods are updated with the new parameter.

I have also added a new utility method to SpeechInputManager to invoke the platform
provided microphone settings UI, this will be used in the next CL which contains
windows, mac and linux specific UI changes.

BUG=69886
TEST=manual, invoke speech input and check the bubble volume indicator to see background noise and clipping.

Review URL: http://codereview.chromium.org/6597071

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@76395 0039d316-1c4b-4281-b951-d872f2087c98

1 files changed, 36 insertions, 7 deletions

diff --git a/content/browser/speech/speech_recognizer.cc b/content/browser/speech/speech_recognizer.cc
index fdc1a4c..b23f4b0 100644
--- a/content/browser/speech/speech_recognizer.cc
+++ b/content/browser/speech/speech_recognizer.cc
@@ -17,11 +17,32 @@ namespace {
 // The following constants are related to the volume level indicator shown in
 // the UI for recorded audio.
 // Multiplier used when new volume is greater than previous level.
-const float kUpSmoothingFactor = 0.9f;
+const float kUpSmoothingFactor = 1.0f;
 // Multiplier used when new volume is lesser than previous level.
-const float kDownSmoothingFactor = 0.4f;
-const float kAudioMeterMinDb = 10.0f;  // Lower bar for volume meter.
-const float kAudioMeterDbRange = 25.0f;
+const float kDownSmoothingFactor = 0.7f;
+// RMS dB value of a maximum (unclipped) sine wave for int16 samples.
+const float kAudioMeterMaxDb = 90.31f;
+// This value corresponds to RMS dB for int16 with 6 most-significant-bits = 0.
+// Values lower than this will display as empty level-meter.
+const float kAudioMeterMinDb = 60.21f;
+const float kAudioMeterDbRange = kAudioMeterMaxDb - kAudioMeterMinDb;
+
+// Maximum level to draw to display unclipped meter. (1.0f displays clipping.)
+const float kAudioMeterRangeMaxUnclipped = 47.0f / 48.0f;
+
+// Returns true if more than 5% of the samples are at min or max value.
+bool Clipping(const int16* samples, int num_samples) {
+  int clipping_samples = 0;
+  const int kThreshold = num_samples / 20;
+  for (int i = 0; i < num_samples; ++i) {
+    if (samples[i] <= -32767 || samples[i] >= 32767) {
+      if (++clipping_samples > kThreshold)
+        return true;
+    }
+  }
+  return false;
+}
+
 }  // namespace
 
 namespace speech_input {
@@ -220,14 +241,22 @@ void SpeechRecognizer::HandleOnData(string* data) {
 
   // Calculate the input volume to display in the UI, smoothing towards the
   // new level.
-  float level = (rms - kAudioMeterMinDb) / kAudioMeterDbRange;
-  level = std::min(std::max(0.0f, level), 1.0f);
+  float level = (rms - kAudioMeterMinDb) /
+      (kAudioMeterDbRange / kAudioMeterRangeMaxUnclipped);
+  level = std::min(std::max(0.0f, level), kAudioMeterRangeMaxUnclipped);
   if (level > audio_level_) {
     audio_level_ += (level - audio_level_) * kUpSmoothingFactor;
   } else {
     audio_level_ += (level - audio_level_) * kDownSmoothingFactor;
   }
-  delegate_->SetInputVolume(caller_id_, audio_level_);
+
+  float noise_level = (endpointer_.NoiseLevelDb() - kAudioMeterMinDb) /
+      (kAudioMeterDbRange / kAudioMeterRangeMaxUnclipped);
+  noise_level = std::min(std::max(0.0f, noise_level),
+      kAudioMeterRangeMaxUnclipped);
+
+  delegate_->SetInputVolume(caller_id_,
+      Clipping(samples, num_samples) ? 1.0f : audio_level_, noise_level);
 
   if (endpointer_.speech_input_complete()) {
     StopRecording();