Adds volume level measurements to the AudioInputController for low-latency clients

media/audio/pulse/pulse_input.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "media/audio/pulse/pulse_input.h"
 
 #include <pulse/pulseaudio.h>
 
 #include "base/logging.h"
+#include "base/time/time.h"
 #include "media/audio/pulse/audio_manager_pulse.h"
 #include "media/audio/pulse/pulse_util.h"
 #include "media/base/seekable_buffer.h"
 
 namespace media {
 
+using base::TimeDelta;
 using pulse::AutoPulseLock;
 using pulse::WaitForOperationCompletion;
 
+static const int kPowerMeasurementTimeConstantMillis = 100;
+
 PulseAudioInputStream::PulseAudioInputStream(AudioManagerPulse* audio_manager,
                                              const std::string& device_name,
                                              const AudioParameters& params,
                                              pa_threaded_mainloop* mainloop,
                                              pa_context* context)
     : audio_manager_(audio_manager),
       callback_(NULL),
       device_name_(device_name),
       params_(params),
       channels_(0),
       volume_(0.0),
       stream_started_(false),
       pa_mainloop_(mainloop),
       pa_context_(context),
       handle_(NULL),
-      context_state_changed_(false) {
+      context_state_changed_(false),
+      audio_level_monitor_(params) {
   DCHECK(mainloop);
   DCHECK(context);
 }
 
 PulseAudioInputStream::~PulseAudioInputStream() {
   // All internal structures should already have been freed in Close(),
   // which calls AudioManagerPulse::Release which deletes this object.
   DCHECK(!handle_);
 }
 
@@ skipping 220 matching lines @@
 
     buffer_->Append(reinterpret_cast<const uint8*>(data), length);
 
     // Checks if we still have data.
     pa_stream_drop(handle_);
   } while (pa_stream_readable_size(handle_) > 0);
 
   int packet_size = params_.GetBytesPerBuffer();
   while (buffer_->forward_bytes() >= packet_size) {
     buffer_->Read(audio_data_buffer_.get(), packet_size);
+
+    audio_level_monitor_.Scan(audio_data_buffer_.get(), packet_size);
+    std::pair<float, bool> result = audio_level_monitor_.ReadCurrentPowerAndClip();
+    float level_dbfs = result.first;
+    float level = 0;
+    static const float kSilenceThresholdDBFS = -72.24719896f;
+    if (level_dbfs < kSilenceThresholdDBFS)
+      level = 0.0f;
+    else if (level_dbfs > 0.0f)
+      level = 1.0f;
+    else
+      level = 1.0f - level_dbfs / kSilenceThresholdDBFS;
+    DVLOG(1) << "PA audio_level: " << level;
+    audio_level_monitor_.Reset();
+
     callback_->OnData(this, audio_data_buffer_.get(), packet_size,
                       hardware_delay, normalized_volume);
 
     if (buffer_->forward_bytes() < packet_size)
       break;
 
     // TODO(xians): Remove once PPAPI is using circular buffers.
     DVLOG(1) << "OnData is being called consecutively, sleep 5ms to "
              << "wait until render consumes the data";
     base::PlatformThread::Sleep(base::TimeDelta::FromMilliseconds(5));
   }
 
   pa_threaded_mainloop_signal(pa_mainloop_, 0);
 }
 
 }  // namespace media