root/media/audio/virtual_audio_input_stream.cc

DEFINITIONS

1. AddInput
2. RemoveInput
3. ProvideInput
4. fake_consumer_
5. Open
6. Start
7. Stop
8. AddOutputStream
9. RemoveOutputStream
10. PumpAudio
11. Close
12. GetMaxVolume
13. SetVolume
14. GetVolume
15. SetAutomaticGainControl
16. GetAutomaticGainControl

// 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/virtual_audio_input_stream.h"

#include <algorithm>
#include <utility>

#include "base/bind.h"
#include "base/single_thread_task_runner.h"
#include "media/audio/virtual_audio_output_stream.h"

namespace media {

// LoopbackAudioConverter works similar to AudioConverter and converts input
// streams to different audio parameters. Then, the LoopbackAudioConverter can
// be used as an input to another AudioConverter. This allows us to
// use converted audio from AudioOutputStreams as input to an AudioConverter.
// For example, this allows converting multiple streams into a common format and
// using the converted audio as input to another AudioConverter (i.e. a mixer).
class LoopbackAudioConverter : public AudioConverter::InputCallback {
 public:
  LoopbackAudioConverter(const AudioParameters& input_params,
                         const AudioParameters& output_params)
      : audio_converter_(input_params, output_params, false) {}

  virtual ~LoopbackAudioConverter() {}

  void AddInput(AudioConverter::InputCallback* input) {
    audio_converter_.AddInput(input);
  }

  void RemoveInput(AudioConverter::InputCallback* input) {
    audio_converter_.RemoveInput(input);
  }

 private:
  virtual double ProvideInput(AudioBus* audio_bus,
                              base::TimeDelta buffer_delay) OVERRIDE {
    audio_converter_.Convert(audio_bus);
    return 1.0;
  }

  AudioConverter audio_converter_;

  DISALLOW_COPY_AND_ASSIGN(LoopbackAudioConverter);
};

VirtualAudioInputStream::VirtualAudioInputStream(
    const AudioParameters& params,
    const scoped_refptr<base::SingleThreadTaskRunner>& worker_task_runner,
    const AfterCloseCallback& after_close_cb)
    : worker_task_runner_(worker_task_runner),
      after_close_cb_(after_close_cb),
      callback_(NULL),
      buffer_(new uint8[params.GetBytesPerBuffer()]),
      params_(params),
      mixer_(params_, params_, false),
      num_attached_output_streams_(0),
      fake_consumer_(worker_task_runner_, params_) {
  DCHECK(params_.IsValid());
  DCHECK(worker_task_runner_.get());

  // VAIS can be constructed on any thread, but will DCHECK that all
  // AudioInputStream methods are called from the same thread.
  thread_checker_.DetachFromThread();
}

VirtualAudioInputStream::~VirtualAudioInputStream() {
  DCHECK(!callback_);

  // Sanity-check: Contract for Add/RemoveOutputStream() requires that all
  // output streams be removed before VirtualAudioInputStream is destroyed.
  DCHECK_EQ(0, num_attached_output_streams_);

  for (AudioConvertersMap::iterator it = converters_.begin();
       it != converters_.end(); ++it) {
    delete it->second;
  }
}

bool VirtualAudioInputStream::Open() {
  DCHECK(thread_checker_.CalledOnValidThread());
  memset(buffer_.get(), 0, params_.GetBytesPerBuffer());
  return true;
}

void VirtualAudioInputStream::Start(AudioInputCallback* callback) {
  DCHECK(thread_checker_.CalledOnValidThread());
  callback_ = callback;
  fake_consumer_.Start(base::Bind(
      &VirtualAudioInputStream::PumpAudio, base::Unretained(this)));
}

void VirtualAudioInputStream::Stop() {
  DCHECK(thread_checker_.CalledOnValidThread());
  fake_consumer_.Stop();
  callback_ = NULL;
}

void VirtualAudioInputStream::AddOutputStream(
    VirtualAudioOutputStream* stream, const AudioParameters& output_params) {
  DCHECK(thread_checker_.CalledOnValidThread());

  base::AutoLock scoped_lock(converter_network_lock_);

  AudioConvertersMap::iterator converter = converters_.find(output_params);
  if (converter == converters_.end()) {
    std::pair<AudioConvertersMap::iterator, bool> result = converters_.insert(
        std::make_pair(output_params,
                       new LoopbackAudioConverter(output_params, params_)));
    converter = result.first;

    // Add to main mixer if we just added a new AudioTransform.
    mixer_.AddInput(converter->second);
  }
  converter->second->AddInput(stream);
  ++num_attached_output_streams_;
}

void VirtualAudioInputStream::RemoveOutputStream(
    VirtualAudioOutputStream* stream, const AudioParameters& output_params) {
  DCHECK(thread_checker_.CalledOnValidThread());

  base::AutoLock scoped_lock(converter_network_lock_);

  DCHECK(converters_.find(output_params) != converters_.end());
  converters_[output_params]->RemoveInput(stream);

  --num_attached_output_streams_;
  DCHECK_LE(0, num_attached_output_streams_);
}

void VirtualAudioInputStream::PumpAudio(AudioBus* audio_bus) {
  DCHECK(worker_task_runner_->BelongsToCurrentThread());

  {
    base::AutoLock scoped_lock(converter_network_lock_);
    mixer_.Convert(audio_bus);
  }
  audio_bus->ToInterleaved(params_.frames_per_buffer(),
                           params_.bits_per_sample() / 8,
                           buffer_.get());
  callback_->OnData(this,
                    buffer_.get(),
                    params_.GetBytesPerBuffer(),
                    params_.GetBytesPerBuffer(),
                    1.0);
}

void VirtualAudioInputStream::Close() {
  DCHECK(thread_checker_.CalledOnValidThread());

  Stop();  // Make sure callback_ is no longer being used.

  // If a non-null AfterCloseCallback was provided to the constructor, invoke it
  // here.  The callback is moved to a stack-local first since |this| could be
  // destroyed during Run().
  if (!after_close_cb_.is_null()) {
    const AfterCloseCallback cb = after_close_cb_;
    after_close_cb_.Reset();
    cb.Run(this);
  }
}

double VirtualAudioInputStream::GetMaxVolume() {
  return 1.0;
}

void VirtualAudioInputStream::SetVolume(double volume) {}

double VirtualAudioInputStream::GetVolume() {
  return 1.0;
}

void VirtualAudioInputStream::SetAutomaticGainControl(bool enabled) {}

bool VirtualAudioInputStream::GetAutomaticGainControl() {
  return false;
}

}  // namespace media