text: // 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/fake_audio_input_stream.h"
  
  #include "base/bind.h"
  #include "base/lazy_instance.h"
  #include "media/audio/audio_manager_base.h"
  
  using base::Time;
  using base::TimeDelta;
  
  namespace media {
  
  namespace {
  
  // These values are based on experiments for local-to-local
  // PeerConnection to demonstrate audio/video synchronization.
  const int kBeepDurationMilliseconds = 20;
  const int kBeepFrequency = 400;
  
  struct BeepContext {
    BeepContext() : beep_once(false) {}
    base::Lock beep_lock;
    bool beep_once;
  };
  
  static base::LazyInstance<BeepContext> g_beep_context =
      LAZY_INSTANCE_INITIALIZER;
  
  }  // namespace
  
  AudioInputStream* FakeAudioInputStream::MakeFakeStream(
      AudioManagerBase* manager,
      const AudioParameters& params) {
    return new FakeAudioInputStream(manager, params);
  }
  
  FakeAudioInputStream::FakeAudioInputStream(AudioManagerBase* manager,
                                             const AudioParameters& params)
      : audio_manager_(manager),
        callback_(NULL),
        buffer_size_((params.channels() * params.bits_per_sample() *
                      params.frames_per_buffer()) / 8),
        params_(params),
        thread_("FakeAudioRecordingThread"),
        callback_interval_(base::TimeDelta::FromMilliseconds(
            (params.frames_per_buffer() * 1000) / params.sample_rate())),
        beep_duration_in_buffers_(
            kBeepDurationMilliseconds * params.sample_rate() /
            params.frames_per_buffer() / 1000),
        beep_generated_in_buffers_(0),
        beep_period_in_frames_(params.sample_rate() / kBeepFrequency),
        frames_elapsed_(0) {
  }
  
  FakeAudioInputStream::~FakeAudioInputStream() {}
  
  bool FakeAudioInputStream::Open() {
    buffer_.reset(new uint8[buffer_size_]);
    memset(buffer_.get(), 0, buffer_size_);
    return true;
  }
  
  void FakeAudioInputStream::Start(AudioInputCallback* callback)  {
    DCHECK(!thread_.IsRunning());
    callback_ = callback;
    last_callback_time_ = Time::Now();
    thread_.Start();
    thread_.message_loop()->PostDelayedTask(
        FROM_HERE,
        base::Bind(&FakeAudioInputStream::DoCallback, base::Unretained(this)),
        callback_interval_);
  }
  
  void FakeAudioInputStream::DoCallback() {
    DCHECK(callback_);
  
    memset(buffer_.get(), 0, buffer_size_);
  
    bool should_beep = false;
    {
      BeepContext* beep_context = g_beep_context.Pointer();
      base::AutoLock auto_lock(beep_context->beep_lock);
      should_beep = beep_context->beep_once;
      beep_context->beep_once = false;
    }
  
    // If this object was instructed to generate a beep or has started to
    // generate a beep sound.
    if (should_beep || beep_generated_in_buffers_) {
      // Compute the number of frames to output high value. Then compute the
      // number of bytes based on channels and bits per channel.
      int high_frames = beep_period_in_frames_ / 2;
      int high_bytes = high_frames * params_.bits_per_sample() *
          params_.channels() / 8;
  
      // Separate high and low with the same number of bytes to generate a
      // square wave.
      int position = 0;
      while (position + high_bytes <= buffer_size_) {
        // Write high values first.
        memset(buffer_.get() + position, 128, high_bytes);
  
        // Then leave low values in the buffer with |high_bytes|.
        position += high_bytes * 2;
      }
  
      ++beep_generated_in_buffers_;
      if (beep_generated_in_buffers_ >= beep_duration_in_buffers_)
        beep_generated_in_buffers_ = 0;
    }
  
    callback_->OnData(this, buffer_.get(), buffer_size_, buffer_size_, 1.0);
    frames_elapsed_ += params_.frames_per_buffer();
  
    Time now = Time::Now();
    base::TimeDelta next_callback_time =
        last_callback_time_ + callback_interval_ * 2 - now;
  
    // If we are falling behind, try to catch up as much as we can in the next
    // callback.
    if (next_callback_time < base::TimeDelta())
      next_callback_time = base::TimeDelta();
  
    last_callback_time_ = now;
    thread_.message_loop()->PostDelayedTask(
        FROM_HERE,
        base::Bind(&FakeAudioInputStream::DoCallback, base::Unretained(this)),
        next_callback_time);
  }
  
  void FakeAudioInputStream::Stop() {
    thread_.Stop();
  }
  
  void FakeAudioInputStream::Close() {
    if (callback_) {
      callback_->OnClose(this);
      callback_ = NULL;
    }
    audio_manager_->ReleaseInputStream(this);
  }
  
  double FakeAudioInputStream::GetMaxVolume() {
    return 1.0;
  }
  
  void FakeAudioInputStream::SetVolume(double volume) {
  }
  
  double FakeAudioInputStream::GetVolume() {
    return 1.0;
  }
  
  void FakeAudioInputStream::SetAutomaticGainControl(bool enabled) {}
  
  bool FakeAudioInputStream::GetAutomaticGainControl() {
    return true;
  }
  
  // static
  void FakeAudioInputStream::BeepOnce() {
    BeepContext* beep_context = g_beep_context.Pointer();
    base::AutoLock auto_lock(beep_context->beep_lock);
    beep_context->beep_once = true;
  }
  
  }  // namespace media
  