Audio output debug recording.

media/audio/audio_debug_recording_helper.cc

+// Copyright 2017 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_debug_recording_helper.h"
+
+#include "base/bind.h"
+#include "base/files/file_path.h"
+#include "base/single_thread_task_runner.h"
+#include "media/audio/audio_manager.h"
+
+namespace media {
+
+AudioDebugRecordingHelper::AudioDebugRecordingHelper(
+    const AudioParameters& params,
+    const CreateAudioFileWriterCallback& create_audio_file_writer_callback,
+    scoped_refptr<base::SingleThreadTaskRunner> task_runner,
+    base::OnceClosure on_destruction_closure)
+    : params_(params),
+      create_audio_file_writer_callback_(create_audio_file_writer_callback),
+      task_runner_(std::move(task_runner)),
+      on_destruction_closure_(std::move(on_destruction_closure)),
+      weak_factory_(this) {
+  DCHECK(create_audio_file_writer_callback_);
+}
+
+AudioDebugRecordingHelper::~AudioDebugRecordingHelper() {
+  if (on_destruction_closure_)
+    std::move(on_destruction_closure_).Run();
+}
+
+void AudioDebugRecordingHelper::EnableDebugRecording(
+    const base::FilePath& file_name) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  DCHECK(!debug_writer_);
+  DCHECK(!file_name.empty());
+
+  debug_writer_ = create_audio_file_writer_callback_.Run(params_);
+  debug_writer_->Start(file_name.AddExtension(debug_writer_->GetExtension()));
+}
+
+void AudioDebugRecordingHelper::DisableDebugRecording() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+
+  if (debug_writer_) {
+    debug_writer_->Stop();
+    debug_writer_.reset();
+  }
+}
+
+void AudioDebugRecordingHelper::OnData(const AudioBus* source) {
+  // This function is normally called on the sound card thread, so there is a
+  // race accessing |debug_writer_|. For this reason, we only check the
+  // pointer, and not |debug_writer_|->WillWrite(). The race checking the
+  // pointer is OK because we'll check again in DoWrite(), and one possible
+  // unnecessary copy when disabling is fine.
+  // Furthermore, |debug_writer_| is always started right after creation, and
+  // stopped right before being reset, and since WillWrite() simply checks
+  // whether started or not, it's not needed either.

[Max Morin, 2017/02/09 09:47:26]

Could you introduce an atomic flag instead?

[o1ka, 2017/02/09 13:04:02]

This is good enough, isn't it? What would we gain having a flag?

[Henrik Grunell, 2017/02/10 09:00:56]

After discussing offline, I decided to use an atomic flag.

+  if (!debug_writer_)
+    return;
+
+  // TODO(grunell) Don't create a new AudioBus each time. Maybe a pool of
+  // AudioBuses. See also comment in
+  // AudioInputController::AudioCallback::PerformOptionalDebugRecording.
+  std::unique_ptr<AudioBus> audio_bus_copy =
+      AudioBus::Create(source->channels(), source->frames());
+  source->CopyTo(audio_bus_copy.get());
+
+  task_runner_->PostTask(
+      FROM_HERE,
+      base::Bind(&AudioDebugRecordingHelper::DoWrite,
+                 weak_factory_.GetWeakPtr(), base::Passed(&audio_bus_copy)));
+}
+
+void AudioDebugRecordingHelper::DoWrite(std::unique_ptr<media::AudioBus> data) {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+
+  if (debug_writer_)
+    debug_writer_->Write(std::move(data));
+}
+
+}  // namespace media