MediaStream audio sourcing: Bypass audio processing for non-WebRTC cases.

content/renderer/media/external_media_stream_audio_source.cc

+// Copyright 2016 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 "content/renderer/media/external_media_stream_audio_source.h"
+
+namespace content {
+
+ExternalMediaStreamAudioSource::ExternalMediaStreamAudioSource(
+    const scoped_refptr<media::AudioCapturerSource>& source,
+    int sample_rate,
+    media::ChannelLayout channel_layout,
+    int frames_per_buffer,
+    bool is_remote)
+    : MediaStreamAudioSource(!is_remote),
+      source_(source),
+      is_started_(false) {
+  DVLOG(1) << "ExternalMediaStreamAudioSource::ExternalMediaStreamAudioSource()";
+  DCHECK(source_.get());
+  MediaStreamAudioSource::SetFormat(media::AudioParameters(
+      media::AudioParameters::AUDIO_PCM_LOW_LATENCY,
+      channel_layout,
+      sample_rate,
+      16,  // Legacy parameter (data is always in 32-bit float format).
+      frames_per_buffer));
+}
+
+ExternalMediaStreamAudioSource::~ExternalMediaStreamAudioSource() {
+  DVLOG(1) << "ExternalMediaStreamAudioSource::~ExternalMediaStreamAudioSource()";
+  // Superclass will call StopSource() just in case.
+}
+
+void ExternalMediaStreamAudioSource::DoStopSource() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (is_stopped_)
+    return;
+  if (is_started_) {
+    source_->Stop();
+    VLOG(1) << "Stopped externally-provided "
+            << (is_local_source() ? "local" : "remote")
+            << " source with audio parameters={"
+            << GetAudioParameters().AsHumanReadableString() << "}.";
+  }
+  is_stopped_ = true;
+}
+
+bool ExternalMediaStreamAudioSource::EnsureSourceIsStarted() {
+  DCHECK(thread_checker_.CalledOnValidThread());
+  if (is_stopped_)
+    return false;
+  if (is_started_)
+    return true;
+  VLOG(1) << "Starting externally-provided "
+          << (is_local_source() ? "local" : "remote")
+          << " source with audio parameters={"
+          << GetAudioParameters().AsHumanReadableString() << "}.";
+  source_->Initialize(GetAudioParameters(), this, -1);
+  source_->Start();
+  is_started_ = true;
+  return true;
+}
+
+void ExternalMediaStreamAudioSource::Capture(const media::AudioBus* audio_bus,
+                                             int audio_delay_milliseconds,
+                                             double volume,
+                                             bool key_pressed) {
+  DCHECK(audio_bus);
+  // TODO(miu): Plumbing is needed to determine the actual capture timestamp
+  // of the audio, instead of just snapshotting TimeTicks::Now(), for proper
+  // audio/video sync.  http://crbug.com/335335
+  MediaStreamAudioSource::DeliverDataToTracks(
+      *audio_bus,
+      base::TimeTicks::Now() -
+          base::TimeDelta::FromMilliseconds(audio_delay_milliseconds));
+}
+
+void ExternalMediaStreamAudioSource::OnCaptureError(const std::string& why) {
+  // As of this writing, this method doesn't get called for anything useful,
+  // and all other implementors just log the message, but don't disconnect sinks
+  // or take any other action.  So, just log the error.
+  LOG(ERROR) << why;
+}
+
+}  // namespace content