Express audio delay more precisely in frames rather than milliseconds.

media/base/audio_renderer_mixer_input.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_input.h"
 
+#include <cmath>
+
 #include "base/bind.h"
 #include "base/callback_helpers.h"
 #include "media/base/audio_renderer_mixer.h"
 
 namespace media {
 
 AudioRendererMixerInput::AudioRendererMixerInput(
     const GetMixerCB& get_mixer_cb,
     const RemoveMixerCB& remove_mixer_cb,
     const std::string& device_id,
@@ skipping 141 matching lines @@
 
 OutputDeviceStatus AudioRendererMixerInput::GetDeviceStatus() {
   if (!mixer_)
     return OUTPUT_DEVICE_STATUS_ERROR_INTERNAL;
 
   return mixer_->GetOutputDevice()->GetDeviceStatus();
 }
 
 double AudioRendererMixerInput::ProvideInput(AudioBus* audio_bus,
                                              base::TimeDelta buffer_delay) {
-  int frames_filled = callback_->Render(
-      audio_bus, static_cast<int>(buffer_delay.InMillisecondsF() + 0.5), 0);
+  // TODO(chcunningham): Delete this conversion and change ProvideInput to more
+  // precisely describe delay as a count of frames delayed instead of TimeDelta.
+  uint32_t frames_delayed = std::round(buffer_delay.InMicroseconds() /

[Henrik Grunell, 2016/02/12 17:47:01]

Any reason to prefer std::round over + 0.5?

[chcunningham, 2016/02/17 01:56:52]

:) Dale asked the same. C-programmer style is not my favorite. I think this is
more readable and I don't see any clear advantage to the alternative. 

[Henrik Grunell, 2016/02/17 08:13:47]

Fine with me. :) I assume std::round is efficient (enough).

+                                       params_.GetMicrosecondsPerFrame());
+
+  int frames_filled = callback_->Render(audio_bus, frames_delayed, 0);
 
   // AudioConverter expects unfilled frames to be zeroed.
   if (frames_filled < audio_bus->frames()) {
     audio_bus->ZeroFramesPartial(
         frames_filled, audio_bus->frames() - frames_filled);
   }
 
   return frames_filled > 0 ? volume_ : 0;
 }
 
 void AudioRendererMixerInput::OnRenderError() {
   callback_->OnRenderError();
 }
 
 }  // namespace media