Browser-wide audio mirroring for TabCapture API

media/audio/virtual_audio_input_stream.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/virtual_audio_input_stream.h"
+
+#include "base/bind.h"
+#include "media/audio/audio_manager_base.h"
+#include "media/audio/audio_output_resampler.h"
+#include "media/audio/virtual_audio_output_stream.h"
+#include "media/audio/audio_util.h"
+
+namespace media {
+
+AudioInputStream* VirtualAudioInputStream::MakeStream(
+    AudioManagerBase* manager, const AudioParameters& params) {
+  return new VirtualAudioInputStream(manager, params);
+}
+
+VirtualAudioInputStream::VirtualAudioInputStream(AudioManagerBase* manager,
+                                                 const AudioParameters& params)
+    : audio_manager_(manager),
+      callback_(NULL),
+      buffer_size_((params.channels() * params.bits_per_sample() *

[DaleCurtis, 2012/11/07 23:34:17]

params.GetBytesPerBuffer() ?

[justinlin, 2012/11/20 08:56:10]

Done.

+                    params.frames_per_buffer()) / 8),
+      params_(params),
+      audio_bus_(AudioBus::Create(params)) {
+}
+
+VirtualAudioInputStream::~VirtualAudioInputStream() {
+}
+
+bool VirtualAudioInputStream::Open() {
+  buffer_.reset(new uint8[buffer_size_]);

[DaleCurtis, 2012/11/07 23:34:17]

Do during constructor.

[justinlin, 2012/11/20 08:56:10]

Done.

+  memset(buffer_.get(), 0, buffer_size_);
+  return true;
+}
+
+void VirtualAudioInputStream::Start(AudioInputCallback* callback) {
+  callback_ = callback;
+  on_more_data_cb_.Reset(base::Bind(
+      &VirtualAudioInputStream::DoCallback, base::Unretained(this)));
+  audio_manager_->GetMessageLoop()->PostTask(
+      FROM_HERE, on_more_data_cb_.callback());
+  // TODO(justinlin): Tell manager to convert all physical streams to
+  // virtual streams.
+}
+
+void VirtualAudioInputStream::DoCallback() {
+  DCHECK(callback_);
+  DCHECK(audio_manager_->GetMessageLoop()->BelongsToCurrentThread());
+
+  int frames_received = 0;
+  float frames_per_millisecond = params_.sample_rate() / static_cast<float>(
+      base::Time::kMillisecondsPerSecond);
+
+  AudioManagerBase::AudioOutputStreamList streams_ =
+      audio_manager_->GetVirtualAudioOutputStreams();
+  for (AudioManagerBase::AudioOutputStreamList::iterator it = streams_.begin();
+       it != streams_.end(); ++it) {
+    const VirtualAudioOutputStream* virtual_output_stream =
+        static_cast<const VirtualAudioOutputStream*>(*it);
+    if (!virtual_output_stream->callback())
+      continue;
+
+    const AudioParameters& virtual_output_stream_params =
+        virtual_output_stream->params();
+
+    // TODO(justinlin): Use array of resamplers?
+    double io_sample_rate_ratio =
+        virtual_output_stream_params.sample_rate() /
+        static_cast<double>(params_.sample_rate());
+    resampler_.reset(new OnMoreDataResampler(

[DaleCurtis, 2012/11/07 23:34:17]

1. You can't just reconstruct this every time due to internal buffers. It should
be associated with the entry in AudioOutputStreamList. I suspect this is why you
have busted audio.

2. We should probably collapse AudioRendererMixer and OnMoreDataResampler into a
common class that does everything. I'll see if I can figure out a clean way to
do that this week.

[justinlin, 2012/11/20 08:56:10]

Done. Thanks!

+        io_sample_rate_ratio, virtual_output_stream_params, params_));
+    resampler_->Start(virtual_output_stream->callback());
+    frames_received =
+        resampler_->OnMoreData(audio_bus_.get(), AudioBuffersState());
+
+    audio_bus_->ToInterleaved(params_.frames_per_buffer(),
+                              params_.bits_per_sample() / 8,
+                              buffer_.get());
+    // TODO(justinlin): Mix streams.
+  }
+
+  callback_->OnData(this, buffer_.get(), buffer_size_, buffer_size_, 1.0);
+
+  MessageLoop::current()->PostDelayedTask(
+      FROM_HERE, on_more_data_cb_.callback(),
+      base::TimeDelta::FromMilliseconds(
+          std::max(1.0f, frames_received / frames_per_millisecond)));
+}
+
+void VirtualAudioInputStream::Stop() {
+  callback_ = NULL; // ?
+  on_more_data_cb_.Cancel();
+  // TODO(justinlin): Notify manager to revert all output streams back
+  // to physical streams.
+}
+
+void VirtualAudioInputStream::Close() {
+  if (callback_) {
+    callback_->OnClose(this);
+    callback_ = NULL;
+  }
+  audio_manager_->ReleaseInputStream(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