Express audio delay more precisely in frames rather than milliseconds.

media/base/audio_renderer_mixer.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/base/audio_renderer_mixer.h"
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
 #include "base/logging.h"
 
 namespace media {
 
 enum { kPauseDelaySeconds = 10 };
 
 AudioRendererMixer::AudioRendererMixer(
     const AudioParameters& output_params,
     const scoped_refptr<AudioRendererSink>& sink)
     : audio_sink_(sink),
       output_params_(output_params),
+      microseconds_per_frame_(

[DaleCurtis, 2016/02/11 01:57:15]

Should we instead have a AudioParameters::GetMicrosecondsPerSecond() call which
returns a double? Seems there might be quite a few call sites.

[chcunningham, 2016/02/11 21:02:52]

Done.

+          static_cast<double>(base::Time::kMicrosecondsPerSecond) /
+          output_params.sample_rate()),
       master_converter_(output_params, output_params, true),
       pause_delay_(base::TimeDelta::FromSeconds(kPauseDelaySeconds)),
       last_play_time_(base::TimeTicks::Now()),
       // Initialize |playing_| to true since Start() results in an auto-play.
       playing_(true) {
   audio_sink_->Initialize(output_params, this);
   audio_sink_->Start();
 }
 
 AudioRendererMixer::~AudioRendererMixer() {
@@ skipping 80 matching lines @@
   NOTREACHED();
 }
 
 OutputDevice* AudioRendererMixer::GetOutputDevice() {
   DVLOG(1) << __FUNCTION__;
   base::AutoLock auto_lock(lock_);
   return audio_sink_->GetOutputDevice();
 }
 
 int AudioRendererMixer::Render(AudioBus* audio_bus,
-                               uint32_t audio_delay_milliseconds,
+                               uint32_t frames_delayed,
                                uint32_t frames_skipped) {
   base::AutoLock auto_lock(lock_);
 
   // If there are no mixer inputs and we haven't seen one for a while, pause the
   // sink to avoid wasting resources when media elements are present but remain
   // in the pause state.
   const base::TimeTicks now = base::TimeTicks::Now();
   if (!master_converter_.empty()) {
     last_play_time_ = now;
   } else if (now - last_play_time_ >= pause_delay_ && playing_) {
     audio_sink_->Pause();
     playing_ = false;
   }
 
-  master_converter_.ConvertWithDelay(
-      base::TimeDelta::FromMilliseconds(audio_delay_milliseconds), audio_bus);
+  base::TimeDelta audio_delay = base::TimeDelta::FromMicroseconds(
+      frames_delayed * microseconds_per_frame_);
+

[DaleCurtis, 2016/02/11 01:57:15]

Mark as TODO: Remove conversion once AudioConverter supports frames instead of
TimeDelta?

[chcunningham, 2016/02/11 21:02:52]

Done.

+  master_converter_.ConvertWithDelay(audio_delay, audio_bus);
   return audio_bus->frames();
 }
 
 void AudioRendererMixer::OnRenderError() {
   // Call each mixer input and signal an error.
   base::AutoLock auto_lock(lock_);
   for (const auto& cb : error_callbacks_)
     cb.Run();
 }
 
 }  // namespace media