media::SilentSinkSuspender should simulate |delay| and |delay_timestamp|

media/base/silent_sink_suspender.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 "media/base/silent_sink_suspender.h"
 
 #include "base/single_thread_task_runner.h"
 #include "base/threading/thread_task_runner_handle.h"
 
 namespace media {
@@ skipping 35 matching lines @@
     // Audio should be silent at this point, if not, it will be handled once the
     // transition to the fake sink is complete.
     dest->Zero();
     return dest->frames();
   }
 
   // When we're using the |fake_sink_| a null destination will be sent; we store
   // the audio data for a future transition out of silence.
   if (!dest) {
     DCHECK(is_using_fake_sink_);
-    DCHECK_EQ(delay, base::TimeDelta());
     DCHECK_EQ(prior_frames_skipped, 0);
+    // |delay_timestamp| contains the value cached at
+    // |fake_sink_transition_time_|
+    // so we simulate the real sink output, promoting |delay_timestamp| with
+    // |elapsedTime|.
+    base::TimeDelta elapsedTime =
+        base::TimeTicks::Now() - fake_sink_transition_time_;
+    delay_timestamp += elapsedTime;

[chcunningham, 2016/12/20 18:36:43]

Could be a little simpler.

// Same comment...
DCHECK_EQ(delay_timestamp, fake_sink_transition_time_);
delay_timestamp = base::TimeTicks::Now()

[Mikhail, 2016/12/20 21:45:50]

sorry, I made a mistake in the comment :( it caches actually
|latest_output_delay_timestamp_|

[chcunningham, 2016/12/21 07:02:54]

No worries. But the core of my comment is about removing the elapsedTime
calculation. Isn't your math equivalent to just setting delay_timestamp =
base::TimeTicks::Now()

 
     // If we have no buffers or a transition is pending, one or more extra
     // Render() calls have occurred in before TransitionSinks() can run, so we
     // store this data for the eventual transition.
     if (buffers_after_silence_.empty() || is_transition_pending_)
       buffers_after_silence_.push_back(AudioBus::Create(params_));
     dest = buffers_after_silence_.back().get();
   } else if (!buffers_after_silence_.empty()) {
     // Drain any non-silent transitional buffers before queuing more audio data.
     // Note: These do not skew clocks derived from frame count since we don't
@@ skipping 15 matching lines @@
       task_runner_->PostTask(
           FROM_HERE, base::Bind(sink_transition_callback_.callback(), false));
       return dest->frames();
     }
   } else if (!is_using_fake_sink_) {
     const base::TimeTicks now = base::TimeTicks::Now();
     if (first_silence_time_.is_null())
       first_silence_time_ = now;
     if (now - first_silence_time_ > silence_timeout_) {
       is_transition_pending_ = true;
+      latest_output_delay_ = delay;
+      latest_output_delay_timestamp_ = delay_timestamp;
+      fake_sink_transition_time_ = now;
       task_runner_->PostTask(
           FROM_HERE, base::Bind(sink_transition_callback_.callback(), true));
     }
   }
 
   return dest->frames();
 }
 
 void SilentSinkSuspender::OnRenderError() {
   callback_->OnRenderError();
@@ skipping 14 matching lines @@
     // after this point, so we must acquire the lock to make sure we don't have
     // concurrent Render() execution. Once |is_using_fake_sink_| is set to true,
     // calls from |sink_| will be dropped.
     {
       base::AutoLock al(transition_lock_);
       is_transition_pending_ = false;
       is_using_fake_sink_ = true;
     }
     fake_sink_.Start(
         base::Bind(base::IgnoreResult(&SilentSinkSuspender::Render),
-                   base::Unretained(this), base::TimeDelta(),
-                   base::TimeTicks::Now(), 0, nullptr));
+                   base::Unretained(this), latest_output_delay_,
+                   latest_output_delay_timestamp_, 0, nullptr));
   } else {
     fake_sink_.Stop();
 
     // Despite the fake sink having a synchronous Stop(), if this transition
     // occurs too soon after pausing the real sink, we may have pending Render()
     // calls from before the transition to the fake sink. As such, we need to
     // hold the lock here to avoid any races.
     {
       base::AutoLock al(transition_lock_);
       is_transition_pending_ = false;
       is_using_fake_sink_ = false;
     }
     sink_->Play();
   }
 }
 
 }  // namespace content