Fix latency plumbing in media::VirtualAudio[Input|Output]Stream.

media/audio/virtual_audio_output_stream.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/audio/virtual_audio_output_stream.h"
 
 #include "base/logging.h"
 #include "media/audio/virtual_audio_input_stream.h"
 
 namespace media {
@@ skipping 59 matching lines @@
   DCHECK(thread_checker_.CalledOnValidThread());
   *volume = volume_;
 }
 
 double VirtualAudioOutputStream::ProvideInput(AudioBus* audio_bus,
                                               base::TimeDelta buffer_delay) {
   // Note: This method may be invoked on any one thread, depending on the
   // platform.
   DCHECK(callback_);
 
-  const int frames = callback_->OnMoreData(audio_bus, 0);
+  DCHECK_GE(buffer_delay, base::TimeDelta());
+  const int64 upstream_delay_in_bytes =
+      params_.GetBytesPerSecond() * buffer_delay /
+          base::TimeDelta::FromSeconds(1);
+  const int frames = callback_->OnMoreData(
+      audio_bus, static_cast<uint32>(upstream_delay_in_bytes));

[hubbe, 2014/12/01 21:56:46]

Is this allowed to not be a multiple of channels*bytes_per_sample?

[miu, 2014/12/02 00:02:44]

The call to GetBytesPerSecond() ensures this, since it will be a multiple of
that expression.

BTW--The "bytes delay" interface is poor (agreed by multiple owners), to be
replaced by a TimeDelta (probably).  There's a bug open for this.

   if (frames < audio_bus->frames())
     audio_bus->ZeroFramesPartial(frames, audio_bus->frames() - frames);
 
   return frames > 0 ? volume_ : 0;
 }
 
 }  // namespace media