Adds Analog Gain Control (AGC) to the WebRTC client.

content/renderer/media/webrtc_audio_device_impl.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 "content/renderer/media/webrtc_audio_device_impl.h"
 
 #include "base/bind.h"
 #include "base/string_util.h"
 #include "base/win/windows_version.h"
 #include "content/renderer/media/audio_hardware.h"
 #include "content/renderer/render_thread_impl.h"
 #include "media/audio/audio_util.h"
 
 static const int64 kMillisecondsBetweenProcessCalls = 5000;
+static const double kMaxVolumeLevel = 255.0;
 
 // Supported hardware sample rates for input and output sides.
 #if defined(OS_WIN) || defined(OS_MACOSX)
 // media::GetAudioInput[Output]HardwareSampleRate() asks the audio layer
 // for its current sample rate (set by the user) on Windows and Mac OS X.
 // The listed rates below adds restrictions and WebRtcAudioDeviceImpl::Init()
 // will fail if the user selects any rate outside these ranges.
 static int kValidInputRates[] = {96000, 48000, 44100, 32000, 16000};
 static int kValidOutputRates[] = {96000, 48000, 44100};
 #elif defined(OS_LINUX) || defined(OS_OPENBSD)
 // media::GetAudioInput[Output]HardwareSampleRate() is hardcoded to return
 // 48000 in both directions on Linux.
 static int kValidInputRates[] = {48000};
 static int kValidOutputRates[] = {48000};
 #endif
 
 WebRtcAudioDeviceImpl::WebRtcAudioDeviceImpl()
     : ref_count_(0),
       render_loop_(base::MessageLoopProxy::current()),
       audio_transport_callback_(NULL),
       input_delay_ms_(0),
       output_delay_ms_(0),
       last_error_(AudioDeviceModule::kAdmErrNone),
       last_process_time_(base::TimeTicks::Now()),
       session_id_(0),
       bytes_per_sample_(0),
       initialized_(false),
       playing_(false),
-      recording_(false) {
+      recording_(false),
+      agc_is_enabled_(false) {
     DVLOG(1) << "WebRtcAudioDeviceImpl::WebRtcAudioDeviceImpl()";
     DCHECK(RenderThreadImpl::current()) <<
         "WebRtcAudioDeviceImpl must be constructed on the render thread";
 }
 
 WebRtcAudioDeviceImpl::~WebRtcAudioDeviceImpl() {
   DVLOG(1) << "WebRtcAudioDeviceImpl::~WebRtcAudioDeviceImpl()";
   if (playing_)
     StopPlayout();
   if (recording_)
@@ skipping 71 matching lines @@
   }
   return number_of_frames;
 }
 
 void WebRtcAudioDeviceImpl::OnRenderError() {
   DCHECK_EQ(MessageLoop::current(), ChildProcess::current()->io_message_loop());
   // TODO(henrika): Implement error handling.
   LOG(ERROR) << "OnRenderError()";
 }
 
-void WebRtcAudioDeviceImpl::Capture(
-    const std::vector<float*>& audio_data,
-    size_t number_of_frames,
-    size_t audio_delay_milliseconds) {
+void WebRtcAudioDeviceImpl::Capture(const std::vector<float*>& audio_data,
+                                    size_t number_of_frames,
+                                    size_t audio_delay_milliseconds,
+                                    double volume) {
   DCHECK_LE(number_of_frames, input_buffer_size());
+ #if defined(OS_WIN) || defined(OS_MACOSX)
+  DCHECK_LE(volume, 1.0);
+ #elif defined(OS_LINUX) || defined(OS_OPENBSD)
+  // We have a special situation on Linux where the microphone volume can be
+  // "higher than maximum". The input volume slider in the sound preference
+  // allows the user to set a scaling that is higher than 100%. It means that
+  // even if the reported maximum levels is N, the actual microphone level can
+  // go up to 1.5*N and that corresponds to a normalized |volume| of 1.5.
+  DCHECK_LE(volume, 1.5);
+ #endif
 
   int output_delay_ms = 0;
   {
     base::AutoLock auto_lock(lock_);
     // Store the reported audio delay locally.
     input_delay_ms_ = audio_delay_milliseconds;
     output_delay_ms = output_delay_ms_;
   }
 
   const int channels = audio_data.size();
   DCHECK_LE(channels, input_channels());
   uint32_t new_mic_level = 0;
 
   // Interleave, scale, and clip input to int16 and store result in
   // a local byte buffer.
   media::InterleaveFloatToInt16(audio_data,
                                 input_buffer_.get(),
                                 number_of_frames);
 
   int samples_per_sec = input_sample_rate();
   if (samples_per_sec == 44100) {
     // Even if the hardware runs at 44.1kHz, we use 44.0 internally.
     samples_per_sec = 44000;
   }
   const int samples_per_10_msec = (samples_per_sec / 100);
   const int bytes_per_10_msec =
       channels * samples_per_10_msec * bytes_per_sample_;
   size_t accumulated_audio_samples = 0;
+  char* audio_byte_buffer = reinterpret_cast<char*>(input_buffer_.get());
 
-  char* audio_byte_buffer = reinterpret_cast<char*>(input_buffer_.get());
+  // Map internal volume range of [0.0, 1.0] into [0, 255] used by the
+  // webrtc::VoiceEngine.
+  uint32_t current_mic_level = static_cast<uint32_t>(volume * kMaxVolumeLevel);
 
   // Write audio samples in blocks of 10 milliseconds to the registered
   // webrtc::AudioTransport sink. Keep writing until our internal byte
   // buffer is empty.
   while (accumulated_audio_samples < number_of_frames) {
-    // Deliver 10ms of recorded PCM audio.
-    // TODO(henrika): add support for analog AGC?
+    // Deliver 10ms of recorded 16-bit linear PCM audio.
     audio_transport_callback_->RecordedDataIsAvailable(
         audio_byte_buffer,
         samples_per_10_msec,
         bytes_per_sample_,
         channels,
         samples_per_sec,
         input_delay_ms_ + output_delay_ms,
-        0,  // clock_drift
-        0,  // current_mic_level
-        new_mic_level);  // not used
+        0,  // TODO(henrika): |clock_drift| parameter is not utilized today.
+        current_mic_level,
+        new_mic_level);
+
     accumulated_audio_samples += samples_per_10_msec;
     audio_byte_buffer += bytes_per_10_msec;
   }
+
+  // The AGC returns a non-zero microphone level if it has been decided
+  // that a new level should be set.
+  if (new_mic_level != 0) {
+    // Use IPC and set the new level. Note that, it will take some time
+    // before the new level is effective due to the IPC scheme.
+    // During this time, |current_mic_level| will contain "non-valid" values
+    // and it might reduce the AGC performance. Measurements on Windows 7 have
+    // shown that we might receive old volume levels for one or two callbacks.
+    SetMicrophoneVolume(new_mic_level);
+  }
 }
 
 void WebRtcAudioDeviceImpl::OnCaptureError() {
   DCHECK_EQ(MessageLoop::current(), ChildProcess::current()->io_message_loop());
   // TODO(henrika): Implement error handling.
   LOG(ERROR) << "OnCaptureError()";
 }
 
 void WebRtcAudioDeviceImpl::OnDeviceStarted(const std::string& device_id) {
   DVLOG(1) << "OnDeviceStarted (device_id=" << device_id << ")";
@@ skipping 468 matching lines @@
   base::AutoLock auto_lock(lock_);
   recording_ = false;
   return 0;
 }
 
 bool WebRtcAudioDeviceImpl::Recording() const {
   return recording_;
 }
 
 int32_t WebRtcAudioDeviceImpl::SetAGC(bool enable) {
-  DVLOG(2) << "WARNING: WebRtcAudioDeviceImpl::SetAGC() " << "NOT IMPLEMENTED";
-  return -1;
+  // The current implementation does not support changing the AGC state while
+  // recording. Using this approach simplifies the design and it is also
+  // inline with the  latest WebRTC standard.
+  DCHECK(!recording_);
+  if (recording_) {
+    DLOG(ERROR) << "Failed to modify the AGC state since recording is active.";
+    return -1;
+  }
+
+  audio_input_device_->SetAutomaticGainControl(enable);

[scherkus (not reviewing), 2012/03/26 22:41:04]

nit: instead of a setter you may consider passing in this value to Start() --
that way we don't have an API that puts restrictions on the ordering of method
calls

[henrika (OOO until Aug 14), 2012/03/27 09:20:38]

Thanks for the proposal. I'd like to keep the current design if that is OK. My
opinion is that calls like: Start(true/false) can look odd.

+  agc_is_enabled_ = enable;
+  return 0;
 }
 
 bool WebRtcAudioDeviceImpl::AGC() const {
-  DVLOG(2) << "WARNING: WebRtcAudioDeviceImpl::AGC() " << "NOT IMPLEMENTED";
-  return false;
+  // To reduce the usage of IPC messages, an internal AGC state is used.
+  // TODO(henrika): investigate if there is a need for a "deeper" getter.
+  return agc_is_enabled_;
 }
 
 int32_t WebRtcAudioDeviceImpl::SetWaveOutVolume(uint16_t volume_left,
                                                 uint16_t volume_right) {
   NOTIMPLEMENTED();
   return -1;
 }
 int32_t WebRtcAudioDeviceImpl::WaveOutVolume(
     uint16_t* volume_left,
     uint16_t* volume_right) const {
@@ skipping 52 matching lines @@
 int32_t WebRtcAudioDeviceImpl::SpeakerVolume(uint32_t* volume) const {
   NOTIMPLEMENTED();
   return -1;
 }
 
 int32_t WebRtcAudioDeviceImpl::MaxSpeakerVolume(uint32_t* max_volume) const {
   NOTIMPLEMENTED();
   return -1;
 }
 
-int32_t WebRtcAudioDeviceImpl::MinSpeakerVolume(
-    uint32_t* min_volume) const {
+int32_t WebRtcAudioDeviceImpl::MinSpeakerVolume(uint32_t* min_volume) const {
   NOTIMPLEMENTED();
   return -1;
 }
 
 int32_t WebRtcAudioDeviceImpl::SpeakerVolumeStepSize(
     uint16_t* step_size) const {
   NOTIMPLEMENTED();
   return -1;
 }
 
 int32_t WebRtcAudioDeviceImpl::MicrophoneVolumeIsAvailable(bool* available) {
   NOTIMPLEMENTED();
   return -1;
 }
 
 int32_t WebRtcAudioDeviceImpl::SetMicrophoneVolume(uint32_t volume) {
-  NOTIMPLEMENTED();
+  DVLOG(1) << "SetMicrophoneVolume(" << volume << ")";
+  if (volume > kMaxVolumeLevel)
+    return -1;
+
+  // WebRTC uses a range of [0, 255] to represent the level of the microphone
+  // volume. The IPC channel between the renderer and browser process works
+  // with doubles in the [0.0, 1.0] range and we have to compensate for that.
+  double normalized_volume = static_cast<double>(volume / kMaxVolumeLevel);
+  audio_input_device_->SetVolume(normalized_volume);
+  return 0;
+}
+
+int32_t WebRtcAudioDeviceImpl::MicrophoneVolume(uint32_t* volume) const {
+  // The microphone level is fed to this class using the Capture() callback
+  // and this external API should not be used. Additional IPC messages are
+  // required if support for this API is ever needed.
+  NOTREACHED();
   return -1;
 }
 
-int32_t WebRtcAudioDeviceImpl::MicrophoneVolume(uint32_t* volume) const {
-  NOTIMPLEMENTED();
-  return -1;
+int32_t WebRtcAudioDeviceImpl::MaxMicrophoneVolume(uint32_t* max_volume) const {
+  *max_volume = kMaxVolumeLevel;
+  return 0;
 }
 
-int32_t WebRtcAudioDeviceImpl::MaxMicrophoneVolume(
-    uint32_t* max_volume) const {
-  DVLOG(2) << "WARNING: WebRtcAudioDeviceImpl::MaxMicrophoneVolume() "
-           << "NOT IMPLEMENTED";
-  return -1;
-}
-
-int32_t WebRtcAudioDeviceImpl::MinMicrophoneVolume(
-    uint32_t* min_volume) const {
-  DVLOG(2) << "WARNING: WebRtcAudioDeviceImpl::MinMicrophoneVolume() "
-           << "NOT IMPLEMENTED";
-  return -1;
+int32_t WebRtcAudioDeviceImpl::MinMicrophoneVolume(uint32_t* min_volume) const {
+  *min_volume = 0;
+  return 0;
 }
 
 int32_t WebRtcAudioDeviceImpl::MicrophoneVolumeStepSize(
     uint16_t* step_size) const {
-  NOTIMPLEMENTED();
+  NOTREACHED();
   return -1;
 }
 
 int32_t WebRtcAudioDeviceImpl::SpeakerMuteIsAvailable(bool* available) {
   NOTIMPLEMENTED();
   return -1;
 }
 
 int32_t WebRtcAudioDeviceImpl::SetSpeakerMute(bool enable) {
   NOTIMPLEMENTED();
@@ skipping 177 matching lines @@
 }
 
 int32_t WebRtcAudioDeviceImpl::GetLoudspeakerStatus(bool* enabled) const {
   NOTIMPLEMENTED();
   return -1;
 }
 
 void WebRtcAudioDeviceImpl::SetSessionId(int session_id) {
   session_id_ = session_id;
 }