Audio software mixer.

media/audio/audio_output_dispatcher_impl.cc

Index: media/audio/audio_output_dispatcher_impl.cc
===================================================================
--- media/audio/audio_output_dispatcher_impl.cc	(revision 0)
+++ media/audio/audio_output_dispatcher_impl.cc	(revision 0)
@@ -0,0 +1,200 @@
+// 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/audio_output_dispatcher_impl.h"
+
+#include <algorithm>
+
+#include "base/bind.h"
+#include "base/compiler_specific.h"
+#include "base/message_loop.h"
+#include "base/time.h"
+#include "media/audio/audio_io.h"
+#include "media/audio/audio_output_proxy.h"
+#include "media/audio/audio_util.h"
+
+namespace media {
+
+AudioOutputDispatcherImpl::AudioOutputDispatcherImpl(
+    AudioManager* audio_manager,
+    const AudioParameters& params,
+    const base::TimeDelta& close_delay)
+    : AudioOutputDispatcher(audio_manager, params),
+      pause_delay_(base::TimeDelta::FromMilliseconds(
+          2 * params.frames_per_buffer() *
+          base::Time::kMillisecondsPerSecond / params.sample_rate())),
+      paused_proxies_(0),
+      ALLOW_THIS_IN_INITIALIZER_LIST(weak_this_(this)),
+      close_timer_(FROM_HERE,
+                   close_delay,
+                   weak_this_.GetWeakPtr(),
+                   &AudioOutputDispatcherImpl::ClosePendingStreams) {
+}
+
+AudioOutputDispatcherImpl::~AudioOutputDispatcherImpl() {
+  DCHECK(proxy_to_physical_map_.empty());
+  DCHECK(idle_streams_.empty());
+  DCHECK(pausing_streams_.empty());
+}
+
+bool AudioOutputDispatcherImpl::OpenStream() {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+
+  paused_proxies_++;
+
+  // Ensure that there is at least one open stream.
+  if (idle_streams_.empty() && !CreateAndOpenStream())
+    return false;
+
+  close_timer_.Reset();
+  return true;
+}
+
+bool AudioOutputDispatcherImpl::StartStream(
+    AudioOutputStream::AudioSourceCallback* callback,
+    AudioOutputProxy* stream_proxy) {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+
+  if (idle_streams_.empty() && !CreateAndOpenStream())
+    return false;
+
+  AudioOutputStream* physical_stream = idle_streams_.back();
+  DCHECK(physical_stream);
+  idle_streams_.pop_back();
+
+  DCHECK_GT(paused_proxies_, 0u);
+  --paused_proxies_;
+
+  close_timer_.Reset();
+
+  // Schedule task to allocate streams for other proxies if we need to.
+  message_loop_->PostTask(FROM_HERE, base::Bind(
+      &AudioOutputDispatcherImpl::OpenTask, weak_this_.GetWeakPtr()));
+
+  double volume = 0;
+  stream_proxy->GetVolume(&volume);
+  physical_stream->SetVolume(volume);
+  physical_stream->Start(callback);
+  proxy_to_physical_map_[stream_proxy] = physical_stream;
+  return true;
+}
+
+void AudioOutputDispatcherImpl::StopStream(AudioOutputProxy* stream_proxy) {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+
+  AudioStreamMap::iterator it = proxy_to_physical_map_.find(stream_proxy);
+  DCHECK(it != proxy_to_physical_map_.end());
+  AudioOutputStream* physical_stream = it->second;
+  proxy_to_physical_map_.erase(it);
+
+  physical_stream->Stop();
+
+  ++paused_proxies_;
+
+  pausing_streams_.push_front(physical_stream);
+
+  // Don't recycle stream until two buffers worth of time has elapsed.
+  message_loop_->PostDelayedTask(
+      FROM_HERE,
+      base::Bind(&AudioOutputDispatcherImpl::StopStreamTask,
+                 weak_this_.GetWeakPtr()),
+      pause_delay_);
+}
+
+void AudioOutputDispatcherImpl::StreamVolumeSet(AudioOutputProxy* stream_proxy,
+                                                double volume) {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+  AudioStreamMap::iterator it = proxy_to_physical_map_.find(stream_proxy);
+  if (it != proxy_to_physical_map_.end()) {
+    AudioOutputStream* physical_stream = it->second;
+    physical_stream->SetVolume(volume);
+  }
+}
+
+void AudioOutputDispatcherImpl::StopStreamTask() {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+
+  if (pausing_streams_.empty())
+    return;
+
+  AudioOutputStream* stream = pausing_streams_.back();
+  pausing_streams_.pop_back();
+  idle_streams_.push_back(stream);
+  close_timer_.Reset();
+}
+
+void AudioOutputDispatcherImpl::CloseStream(AudioOutputProxy* stream_proxy) {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+
+  while (!pausing_streams_.empty()) {
+    idle_streams_.push_back(pausing_streams_.back());
+    pausing_streams_.pop_back();
+  }
+
+  DCHECK_GT(paused_proxies_, 0u);
+  paused_proxies_--;
+
+  while (idle_streams_.size() > paused_proxies_) {
+    idle_streams_.back()->Close();
+    idle_streams_.pop_back();
+  }
+}
+
+void AudioOutputDispatcherImpl::Shutdown() {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+
+  // Cancel any pending tasks to close paused streams or create new ones.
+  weak_this_.InvalidateWeakPtrs();
+
+  // No AudioOutputProxy objects should hold a reference to us when we get
+  // to this stage.
+  DCHECK(HasOneRef()) << "Only the AudioManager should hold a reference";
+
+  AudioOutputStreamList::iterator it = idle_streams_.begin();
+  for (; it != idle_streams_.end(); ++it)
+    (*it)->Close();
+  idle_streams_.clear();
+
+  it = pausing_streams_.begin();
+  for (; it != pausing_streams_.end(); ++it)
+    (*it)->Close();
+  pausing_streams_.clear();
+}
+
+bool AudioOutputDispatcherImpl::CreateAndOpenStream() {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+  AudioOutputStream* stream = audio_manager_->MakeAudioOutputStream(params_);
+  if (!stream)
+    return false;
+
+  if (!stream->Open()) {
+    stream->Close();
+    return false;
+  }
+  idle_streams_.push_back(stream);
+  return true;
+}
+
+void AudioOutputDispatcherImpl::OpenTask() {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+  // Make sure that we have at least one stream allocated if there
+  // are paused streams.
+  if (paused_proxies_ > 0 && idle_streams_.empty() &&
+      pausing_streams_.empty()) {
+    CreateAndOpenStream();
+  }
+
+  close_timer_.Reset();
+}
+
+// This method is called by |close_timer_|.
+void AudioOutputDispatcherImpl::ClosePendingStreams() {
+  DCHECK_EQ(MessageLoop::current(), message_loop_);
+  while (!idle_streams_.empty()) {
+    idle_streams_.back()->Close();
+    idle_streams_.pop_back();
+  }
+}
+
+}  // namespace media