Introduce media::AudioPushFifo and a couple of use cases (and clean-ups).

chrome/renderer/media/cast_receiver_audio_valve.cc

 // Copyright 2015 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 "chrome/renderer/media/cast_receiver_audio_valve.h"
 
+#include "base/bind.h"
+#include "base/bind_helpers.h"
+#include "media/audio/audio_parameters.h"
+
 CastReceiverAudioValve::CastReceiverAudioValve(
+    const media::AudioParameters& params,
     media::AudioCapturerSource::CaptureCallback* cb)
-    : cb_(cb) {
+    : cb_(cb),
+      fifo_(base::Bind(&CastReceiverAudioValve::DeliverRebufferedAudio,
+                       base::Unretained(this))),
+      sample_rate_(params.sample_rate()) {
+  fifo_.Reset(params.frames_per_buffer());
 }
+
 CastReceiverAudioValve::~CastReceiverAudioValve() {}
 
-void CastReceiverAudioValve::Capture(const media::AudioBus* audio_source,
-                                     int audio_delay_milliseconds,
-                                     double volume,
-                                     bool key_pressed) {
+void CastReceiverAudioValve::DeliverDecodedAudio(
+    const media::AudioBus* audio_bus,
+    base::TimeTicks playout_time) {
+  current_playout_time_ = playout_time;
+  // The following will result in zero, one, or multiple synchronous calls to
+  // DeliverRebufferedAudio().
+  fifo_.Push(*audio_bus);
+}
+
+void CastReceiverAudioValve::DeliverRebufferedAudio(
+    const media::AudioBus& audio_bus,
+    int frame_delay) {
+  const base::TimeTicks playout_time =
+      current_playout_time_ +
+      base::TimeDelta::FromMicroseconds(
+          frame_delay * base::Time::kMicrosecondsPerSecond / sample_rate_);
+
   base::AutoLock lock(lock_);
   if (cb_) {
-    cb_->Capture(audio_source, audio_delay_milliseconds, volume, key_pressed);
+    // The AudioCapturerSource::Callback interface provides timing information
+    // only as a relative delay value that means "captured N milliseconds ago."
+    // Therefore, translate the playout time to these semantics.  Since playout
+    // time is generally in the future, because audio should be decoded well
+    // ahead of when it should be played out, the audio delay value will
+    // generally be negative.
+    //
+    // TimeTicks::Now() is being called after the |lock_| was acquired in order
+    // to provide the most accurate delay value.
+    const int audio_delay_milliseconds =
+        (base::TimeTicks::Now() - playout_time).InMilliseconds();
+
+    cb_->Capture(&audio_bus, audio_delay_milliseconds, 1.0 /* volume */,
+                 false /* key_pressed */);
   }
 }
 
-void CastReceiverAudioValve::OnCaptureError(const std::string& message) {
-  base::AutoLock lock(lock_);
-  if (cb_) {
-    cb_->OnCaptureError(message);
-  }
-}
-
 void CastReceiverAudioValve::Stop() {
   base::AutoLock lock(lock_);
   cb_ = nullptr;
 }