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

content/renderer/media/track_audio_renderer.cc

Index: content/renderer/media/track_audio_renderer.cc
diff --git a/content/renderer/media/webrtc_local_audio_renderer.cc b/content/renderer/media/track_audio_renderer.cc
similarity index 39%
rename from content/renderer/media/webrtc_local_audio_renderer.cc
rename to content/renderer/media/track_audio_renderer.cc
index f39a017b94db441164f527fba3b8790aca8d46b0..a02f4c4ee9a8f19d639797e8395442f13a3b8307 100644
--- a/content/renderer/media/webrtc_local_audio_renderer.cc
+++ b/content/renderer/media/track_audio_renderer.cc
@@ -2,9 +2,7 @@
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
-#include "content/renderer/media/webrtc_local_audio_renderer.h"
-
-#include <utility>
+#include "content/renderer/media/track_audio_renderer.h"
 
 #include "base/location.h"
 #include "base/logging.h"
@@ -13,10 +11,7 @@
 #include "base/thread_task_runner_handle.h"
 #include "base/trace_event/trace_event.h"
 #include "content/renderer/media/audio_device_factory.h"
-#include "content/renderer/media/media_stream_dispatcher.h"
-#include "content/renderer/media/webrtc_audio_capturer.h"
-#include "content/renderer/media/webrtc_audio_renderer.h"
-#include "content/renderer/render_frame_impl.h"
+#include "content/renderer/media/media_stream_audio_track.h"
 #include "media/audio/audio_output_device.h"
 #include "media/base/audio_bus.h"
 #include "media/base/audio_shifter.h"
@@ -31,95 +26,123 @@ enum LocalRendererSinkStates {
   kSinkStatesMax  // Must always be last!
 };
 
+// Translates |num_samples_rendered| into a TimeDelta duration and adds it to
+// |prior_elapsed_render_time|.
+base::TimeDelta ComputeTotalElapsedRenderTime(
+    base::TimeDelta prior_elapsed_render_time,
+    int64_t num_samples_rendered,
+    int sample_rate) {
+  return prior_elapsed_render_time + base::TimeDelta::FromMicroseconds(
+      num_samples_rendered * base::Time::kMicrosecondsPerSecond / sample_rate);
+}
+
 }  // namespace
 
 // media::AudioRendererSink::RenderCallback implementation
-int WebRtcLocalAudioRenderer::Render(media::AudioBus* audio_bus,
-                                     uint32_t audio_delay_milliseconds,
-                                     uint32_t frames_skipped) {
-  TRACE_EVENT0("audio", "WebRtcLocalAudioRenderer::Render");
+int TrackAudioRenderer::Render(media::AudioBus* audio_bus,
+                               uint32_t audio_delay_milliseconds,
+                               uint32_t frames_skipped) {
+  TRACE_EVENT0("audio", "TrackAudioRenderer::Render");
   base::AutoLock auto_lock(thread_lock_);
 
-  if (!playing_ || !volume_ || !audio_shifter_) {
+  if (!audio_shifter_) {
     audio_bus->Zero();
     return 0;
   }
 
-  audio_shifter_->Pull(
-      audio_bus,
-      base::TimeTicks::Now() -
-      base::TimeDelta::FromMilliseconds(audio_delay_milliseconds));
-
+  // TODO(miu): Plumbing is needed to determine the actual playout timestamp
+  // of the audio, instead of just snapshotting TimeTicks::Now(), for proper
+  // audio/video sync.  http://crbug.com/335335
+  const base::TimeTicks playout_time =
+      base::TimeTicks::Now() +
+      base::TimeDelta::FromMilliseconds(audio_delay_milliseconds);
+  DVLOG(2) << "Pulling audio out of shifter to be played "
+           << audio_delay_milliseconds << " ms from now.";
+  audio_shifter_->Pull(audio_bus, playout_time);
+  num_samples_rendered_ += audio_bus->frames();
   return audio_bus->frames();
 }
 
-void WebRtcLocalAudioRenderer::OnRenderError() {
+void TrackAudioRenderer::OnRenderError() {
   NOTIMPLEMENTED();
 }
 
 // content::MediaStreamAudioSink implementation
-void WebRtcLocalAudioRenderer::OnData(const media::AudioBus& audio_bus,
-                                      base::TimeTicks estimated_capture_time) {
-  DCHECK(capture_thread_checker_.CalledOnValidThread());
-  DCHECK(!estimated_capture_time.is_null());
+void TrackAudioRenderer::OnData(const media::AudioBus& audio_bus,
+                                base::TimeTicks reference_time) {
+  DCHECK(audio_thread_checker_.CalledOnValidThread());
+  DCHECK(!reference_time.is_null());
 
-  TRACE_EVENT0("audio", "WebRtcLocalAudioRenderer::CaptureData");
+  TRACE_EVENT0("audio", "TrackAudioRenderer::CaptureData");
 
   base::AutoLock auto_lock(thread_lock_);
-  if (!playing_ || !volume_ || !audio_shifter_)
+  if (!audio_shifter_)
     return;
 
   scoped_ptr<media::AudioBus> audio_data(
       media::AudioBus::Create(audio_bus.channels(), audio_bus.frames()));
   audio_bus.CopyTo(audio_data.get());
-  audio_shifter_->Push(std::move(audio_data), estimated_capture_time);
-  const base::TimeTicks now = base::TimeTicks::Now();
-  total_render_time_ += now - last_render_time_;
-  last_render_time_ = now;
+  // Note: For remote audio sources, |reference_time| is the local playout time,
+  // the ideal point-in-time at which the first audio sample should be played
+  // out in the future.  For local sources, |reference_time| is the
+  // point-in-time at which the first audio sample was captured in the past.  In
+  // either case, AudioShifter will auto-detect and do the right thing when
+  // audio is pulled from it.
+  audio_shifter_->Push(std::move(audio_data), reference_time);
 }
 
-void WebRtcLocalAudioRenderer::OnSetFormat(
-    const media::AudioParameters& params) {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::OnSetFormat()";
+void TrackAudioRenderer::OnSetFormat(const media::AudioParameters& params) {
+  DVLOG(1) << "TrackAudioRenderer::OnSetFormat()";
   // If the source is restarted, we might have changed to another capture
   // thread.
-  capture_thread_checker_.DetachFromThread();
-  DCHECK(capture_thread_checker_.CalledOnValidThread());
+  audio_thread_checker_.DetachFromThread();
+  DCHECK(audio_thread_checker_.CalledOnValidThread());
+
+  // If the parameters changed, the audio in the AudioShifter is invalid and
+  // should be dropped.
+  {
+    base::AutoLock auto_lock(thread_lock_);
+    if (audio_shifter_ &&
+        (audio_shifter_->sample_rate() != params.sample_rate() ||
+         audio_shifter_->channels() != params.channels())) {
+      HaltAudioFlowWhileLockHeld();
+    }
+  }
 
   // Post a task on the main render thread to reconfigure the |sink_| with the
   // new format.
   task_runner_->PostTask(
       FROM_HERE,
-      base::Bind(&WebRtcLocalAudioRenderer::ReconfigureSink, this, params));
+      base::Bind(&TrackAudioRenderer::ReconfigureSink, this, params));
 }
 
-// WebRtcLocalAudioRenderer::WebRtcLocalAudioRenderer implementation.
-WebRtcLocalAudioRenderer::WebRtcLocalAudioRenderer(
+TrackAudioRenderer::TrackAudioRenderer(
     const blink::WebMediaStreamTrack& audio_track,
-    int source_render_frame_id,
+    int playout_render_frame_id,
     int session_id,
     const std::string& device_id,
     const url::Origin& security_origin)
     : audio_track_(audio_track),
-      source_render_frame_id_(source_render_frame_id),
+      playout_render_frame_id_(playout_render_frame_id),
       session_id_(session_id),
       task_runner_(base::ThreadTaskRunnerHandle::Get()),
+      num_samples_rendered_(0),
       playing_(false),
       output_device_id_(device_id),
       security_origin_(security_origin),
       volume_(0.0),
       sink_started_(false) {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::WebRtcLocalAudioRenderer()";
+  DVLOG(1) << "TrackAudioRenderer::TrackAudioRenderer()";
 }
 
-WebRtcLocalAudioRenderer::~WebRtcLocalAudioRenderer() {
+TrackAudioRenderer::~TrackAudioRenderer() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   DCHECK(!sink_.get());
-  DVLOG(1) << "WebRtcLocalAudioRenderer::~WebRtcLocalAudioRenderer()";
+  DVLOG(1) << "TrackAudioRenderer::~TrackAudioRenderer()";
 }
 
-void WebRtcLocalAudioRenderer::Start() {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::Start()";
+void TrackAudioRenderer::Start() {
+  DVLOG(1) << "TrackAudioRenderer::Start()";
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   // We get audio data from |audio_track_|...
@@ -127,22 +150,26 @@ void WebRtcLocalAudioRenderer::Start() {
   // ...and |sink_| will get audio data from us.
   DCHECK(!sink_.get());
   sink_ =
-      AudioDeviceFactory::NewOutputDevice(source_render_frame_id_, session_id_,
+      AudioDeviceFactory::NewOutputDevice(playout_render_frame_id_, session_id_,
                                           output_device_id_, security_origin_);
+  sink_->SetVolume(volume_);
 
-  base::AutoLock auto_lock(thread_lock_);
-  last_render_time_ = base::TimeTicks::Now();
   playing_ = false;

[tommi (sloooow) - chröme, 2016/02/01 20:32:24]

shouldn't this be assumed to be false already? i.e. dcheck instead?

[miu, 2016/02/03 03:48:45]

Good point.  Done.

+
+  base::AutoLock auto_lock(thread_lock_);
+  prior_elapsed_render_time_ = base::TimeDelta();
+  num_samples_rendered_ = 0;
 }
 
-void WebRtcLocalAudioRenderer::Stop() {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::Stop()";
+void TrackAudioRenderer::Stop() {
+  DVLOG(1) << "TrackAudioRenderer::Stop()";
   DCHECK(task_runner_->BelongsToCurrentThread());
 
+  playing_ = false;

[tommi (sloooow) - chröme, 2016/02/01 20:32:24]

Call Pause()?

[miu, 2016/02/03 03:48:45]

Done.

+
   {
     base::AutoLock auto_lock(thread_lock_);
-    playing_ = false;
-    audio_shifter_.reset();
+    HaltAudioFlowWhileLockHeld();
   }
 
   // Stop the output audio stream, i.e, stop asking for data to render.
@@ -153,7 +180,7 @@ void WebRtcLocalAudioRenderer::Stop() {
     sink_ = NULL;
   }
 
-  if (!sink_started_) {
+  if (!sink_started_ && IsLocalRenderer()) {
     UMA_HISTOGRAM_ENUMERATION("Media.LocalRendererSinkStates",
                               kSinkNeverStarted, kSinkStatesMax);
   }
@@ -163,83 +190,79 @@ void WebRtcLocalAudioRenderer::Stop() {
   MediaStreamAudioSink::RemoveFromAudioTrack(this, audio_track_);
 }
 
-void WebRtcLocalAudioRenderer::Play() {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::Play()";
+void TrackAudioRenderer::Play() {
+  DVLOG(1) << "TrackAudioRenderer::Play()";
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   if (!sink_.get())
     return;
 
-  {
-    base::AutoLock auto_lock(thread_lock_);
-    // Resumes rendering by ensuring that WebRtcLocalAudioRenderer::Render()
-    // now reads data from the local FIFO.
-    playing_ = true;
-    last_render_time_ = base::TimeTicks::Now();
-  }
+  playing_ = true;
 
-  // Note: If volume_ is currently muted, the |sink_| will not be started yet.
   MaybeStartSink();
 }
 
-void WebRtcLocalAudioRenderer::Pause() {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::Pause()";
+void TrackAudioRenderer::Pause() {
+  DVLOG(1) << "TrackAudioRenderer::Pause()";
   DCHECK(task_runner_->BelongsToCurrentThread());
 
   if (!sink_.get())
     return;
 
-  base::AutoLock auto_lock(thread_lock_);
-  // Temporarily suspends rendering audio.
-  // WebRtcLocalAudioRenderer::Render() will return early during this state
-  // and only zeros will be provided to the active sink.
   playing_ = false;
+
+  base::AutoLock auto_lock(thread_lock_);
+  HaltAudioFlowWhileLockHeld();
 }
 
-void WebRtcLocalAudioRenderer::SetVolume(float volume) {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::SetVolume(" << volume << ")";
+void TrackAudioRenderer::SetVolume(float volume) {
+  DVLOG(1) << "TrackAudioRenderer::SetVolume(" << volume << ")";
   DCHECK(task_runner_->BelongsToCurrentThread());
 
-  {
-    base::AutoLock auto_lock(thread_lock_);
-    // Cache the volume.
-    volume_ = volume;
-  }
-
-  // Lazily start the |sink_| when the local renderer is unmuted during
-  // playing.
-  MaybeStartSink();
-
+  // Cache the volume.

[tommi (sloooow) - chröme, 2016/02/01 20:32:24]

Maybe document why we do this instead?

[miu, 2016/02/03 03:48:45]

Done.

+  volume_ = volume;
   if (sink_.get())
     sink_->SetVolume(volume);
 }
 
-media::OutputDevice* WebRtcLocalAudioRenderer::GetOutputDevice() {
+media::OutputDevice* TrackAudioRenderer::GetOutputDevice() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   return this;
 }
 
-base::TimeDelta WebRtcLocalAudioRenderer::GetCurrentRenderTime() const {
+base::TimeDelta TrackAudioRenderer::GetCurrentRenderTime() const {
   DCHECK(task_runner_->BelongsToCurrentThread());
   base::AutoLock auto_lock(thread_lock_);
-  if (!sink_.get())
-    return base::TimeDelta();
-  return total_render_time();
+  if (source_params_.IsValid()) {
+    return ComputeTotalElapsedRenderTime(prior_elapsed_render_time_,
+                                         num_samples_rendered_,
+                                         source_params_.sample_rate());
+  }
+  return prior_elapsed_render_time_;
 }
 
-bool WebRtcLocalAudioRenderer::IsLocalRenderer() const {
-  return true;
+bool TrackAudioRenderer::IsLocalRenderer() const {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+  MediaStreamAudioTrack* const track =
+      MediaStreamAudioTrack::GetTrack(audio_track_);
+  CHECK(track);

[tommi (sloooow) - chröme, 2016/02/01 20:32:24]

nit: not needed due to the next line

[miu, 2016/02/03 03:48:45]

Cleaned this up: I moved the null-check to the constructor and made this a
simple one-liner.

+  return track->is_local_track();
 }
 
-void WebRtcLocalAudioRenderer::SwitchOutputDevice(
+void TrackAudioRenderer::SwitchOutputDevice(
     const std::string& device_id,
     const url::Origin& security_origin,
     const media::SwitchOutputDeviceCB& callback) {
-  DVLOG(1) << "WebRtcLocalAudioRenderer::SwitchOutputDevice()";
+  DVLOG(1) << "TrackAudioRenderer::SwitchOutputDevice()";
   DCHECK(task_runner_->BelongsToCurrentThread());
 
+  {
+    base::AutoLock auto_lock(thread_lock_);
+    HaltAudioFlowWhileLockHeld();
+  }
+
   scoped_refptr<media::AudioOutputDevice> new_sink =
-      AudioDeviceFactory::NewOutputDevice(source_render_frame_id_, session_id_,
+      AudioDeviceFactory::NewOutputDevice(playout_render_frame_id_, session_id_,
                                           device_id, security_origin);
   if (new_sink->GetDeviceStatus() != media::OUTPUT_DEVICE_STATUS_OK) {
     callback.Run(new_sink->GetDeviceStatus());
@@ -255,26 +278,29 @@ void WebRtcLocalAudioRenderer::SwitchOutputDevice(
 
   sink_started_ = false;
   sink_ = new_sink;
-  int frames_per_buffer = sink_->GetOutputParameters().frames_per_buffer();
-  sink_params_ = source_params_;
-  sink_params_.set_frames_per_buffer(WebRtcAudioRenderer::GetOptimalBufferSize(
-      source_params_.sample_rate(), frames_per_buffer));
-
+  sink_->SetVolume(volume_);
   if (was_sink_started)
     MaybeStartSink();
 
   callback.Run(media::OUTPUT_DEVICE_STATUS_OK);
 }
 
-media::AudioParameters WebRtcLocalAudioRenderer::GetOutputParameters() {
+media::AudioParameters TrackAudioRenderer::GetOutputParameters() {
   DCHECK(task_runner_->BelongsToCurrentThread());
-  if (!sink_.get())
+  if (!sink_ || !source_params_.IsValid())
     return media::AudioParameters();
 
-  return sink_->GetOutputParameters();
+  // Output parameters consist of the same channel layout and sample rate as the
+  // source, but having the buffer duration preferred by the hardware.
+  const media::AudioParameters& preferred_params = sink_->GetOutputParameters();
+  return media::AudioParameters(
+      preferred_params.format(), source_params_.channel_layout(),
+      source_params_.sample_rate(), source_params_.bits_per_sample(),
+      preferred_params.frames_per_buffer() * source_params_.sample_rate() /
+          preferred_params.sample_rate());
 }
 
-media::OutputDeviceStatus WebRtcLocalAudioRenderer::GetDeviceStatus() {
+media::OutputDeviceStatus TrackAudioRenderer::GetDeviceStatus() {
   DCHECK(task_runner_->BelongsToCurrentThread());
   if (!sink_.get())
     return media::OUTPUT_DEVICE_STATUS_ERROR_INTERNAL;
@@ -282,75 +308,93 @@ media::OutputDeviceStatus WebRtcLocalAudioRenderer::GetDeviceStatus() {
   return sink_->GetDeviceStatus();
 }
 
-void WebRtcLocalAudioRenderer::MaybeStartSink() {
+void TrackAudioRenderer::MaybeStartSink() {
   DCHECK(task_runner_->BelongsToCurrentThread());
-  DVLOG(1) << "WebRtcLocalAudioRenderer::MaybeStartSink()";
+  DVLOG(1) << "TrackAudioRenderer::MaybeStartSink()";
 
-  if (!sink_.get() || !source_params_.IsValid())
+  if (!sink_.get() || !source_params_.IsValid() || !playing_)
     return;
 
-  {
-    // Clear up the old data in the FIFO.
-    base::AutoLock auto_lock(thread_lock_);
-    audio_shifter_->Flush();
-  }
+  // Re-create the AudioShifter to drop old audio data and reset to a starting
+  // state.  MaybeStartSink() is always called in a situation where either the
+  // source or sink has changed somehow and so all of AudioShifter's internal
+  // time-sync state is invalid.
+  CreateAudioShifter();
 
-  if (!sink_params_.IsValid() || !playing_ || !volume_ || sink_started_ ||
+  if (sink_started_ ||
       sink_->GetDeviceStatus() != media::OUTPUT_DEVICE_STATUS_OK)

[tommi (sloooow) - chröme, 2016/02/01 20:32:24]

nit: add {}?

[miu, 2016/02/03 03:48:45]

Done.

     return;
 
-  DVLOG(1) << "WebRtcLocalAudioRenderer::MaybeStartSink() -- Starting sink_.";
-  sink_->Initialize(sink_params_, this);
+  DVLOG(1) << ("TrackAudioRenderer::MaybeStartSink() -- Starting sink.  "
+               "source_params_={")
+           << source_params_.AsHumanReadableString() << "}, sink parameters={"
+           << GetOutputParameters().AsHumanReadableString() << '}';
+  sink_->Initialize(GetOutputParameters(), this);
   sink_->Start();
   sink_started_ = true;
-  UMA_HISTOGRAM_ENUMERATION("Media.LocalRendererSinkStates",
-                            kSinkStarted, kSinkStatesMax);
+  if (IsLocalRenderer()) {
+    UMA_HISTOGRAM_ENUMERATION("Media.LocalRendererSinkStates", kSinkStarted,
+                              kSinkStatesMax);
+  }
 }
 
-void WebRtcLocalAudioRenderer::ReconfigureSink(
-    const media::AudioParameters& params) {
+void TrackAudioRenderer::ReconfigureSink(const media::AudioParameters& params) {
   DCHECK(task_runner_->BelongsToCurrentThread());
 
-  DVLOG(1) << "WebRtcLocalAudioRenderer::ReconfigureSink()";
+  DVLOG(1) << "TrackAudioRenderer::ReconfigureSink()";
 
   if (source_params_.Equals(params))
     return;
-
-  // Reset the |source_params_|, |sink_params_| and |loopback_fifo_| to match
-  // the new format.
-
   source_params_ = params;
-  {
-    // Note: The max buffer is fairly large, but will rarely be used.
-    // Cast needs the buffer to hold at least one second of audio.
-    // The clock accuracy is set to 20ms because clock accuracy is
-    // ~15ms on windows.
-    media::AudioShifter* const new_shifter = new media::AudioShifter(
-        base::TimeDelta::FromSeconds(2),
-        base::TimeDelta::FromMilliseconds(20),
-        base::TimeDelta::FromSeconds(20),
-        source_params_.sample_rate(),
-        params.channels());
-
-    base::AutoLock auto_lock(thread_lock_);
-    audio_shifter_.reset(new_shifter);
-  }
 
   if (!sink_.get())
-    return;  // WebRtcLocalAudioRenderer has not yet been started.
+    return;  // TrackAudioRenderer has not yet been started.
 
   // Stop |sink_| and re-create a new one to be initialized with different audio
   // parameters.  Then, invoke MaybeStartSink() to restart everything again.
   sink_->Stop();
   sink_started_ = false;
   sink_ =
-      AudioDeviceFactory::NewOutputDevice(source_render_frame_id_, session_id_,
+      AudioDeviceFactory::NewOutputDevice(playout_render_frame_id_, session_id_,
                                           output_device_id_, security_origin_);
-  int frames_per_buffer = sink_->GetOutputParameters().frames_per_buffer();
-  sink_params_ = source_params_;
-  sink_params_.set_frames_per_buffer(WebRtcAudioRenderer::GetOptimalBufferSize(
-      source_params_.sample_rate(), frames_per_buffer));
+  sink_->SetVolume(volume_);
   MaybeStartSink();
 }
 
+void TrackAudioRenderer::CreateAudioShifter() {
+  DCHECK(task_runner_->BelongsToCurrentThread());
+
+  // Note 1: The max buffer is fairly large to cover the case where
+  // remotely-sourced audio is delivered well ahead of its scheduled playout
+  // time (e.g., content streaming with a very large end-to-end
+  // latency). However, there is no penalty for making it large in the
+  // low-latency use cases since AudioShifter will discard data as soon as it is
+  // no longer needed.
+  //
+  // Note 2: The clock accuracy is set to 20ms because clock accuracy is
+  // ~15ms on Windows machines without a working high-resolution clock.  See
+  // comments in base/time/time.h for details.
+  media::AudioShifter* const new_shifter = new media::AudioShifter(

[tommi (sloooow) - chröme, 2016/02/01 20:32:24]

thanks for keeping the scope of the lock down :)

[miu, 2016/02/03 03:48:45]

Acknowledged.

+      base::TimeDelta::FromSeconds(5), base::TimeDelta::FromMilliseconds(20),
+      base::TimeDelta::FromSeconds(20), source_params_.sample_rate(),
+      source_params_.channels());
+
+  base::AutoLock auto_lock(thread_lock_);
+  audio_shifter_.reset(new_shifter);
+}
+
+void TrackAudioRenderer::HaltAudioFlowWhileLockHeld() {
+  thread_lock_.AssertAcquired();
+
+  audio_shifter_.reset();
+
+  if (source_params_.IsValid()) {
+    prior_elapsed_render_time_ =
+        ComputeTotalElapsedRenderTime(prior_elapsed_render_time_,
+                                      num_samples_rendered_,
+                                      source_params_.sample_rate());
+    num_samples_rendered_ = 0;
+  }
+}
+
 }  // namespace content