Switch audio synchronization from sleep() based to select() based.

media/audio/audio_output_controller.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/audio_output_controller.h"
 
 #include "base/bind.h"
 #include "base/debug/trace_event.h"
 #include "base/message_loop/message_loop.h"
 #include "base/metrics/histogram.h"
 #include "base/threading/platform_thread.h"
 #include "base/time/time.h"
 #include "build/build_config.h"
-#include "media/audio/shared_memory_util.h"
 #include "media/base/scoped_histogram_timer.h"
 
 using base::Time;
 using base::TimeDelta;
 
 namespace media {
 
 #if defined(AUDIO_POWER_MONITORING)
 // Time constant for AudioPowerMonitor.  See AudioPowerMonitor ctor comments for
 // semantics.  This value was arbitrarily chosen, but seems to work well.
@@ skipping 189 matching lines @@
 
 void AudioOutputController::DoPause() {
   DCHECK(message_loop_->BelongsToCurrentThread());
   SCOPED_UMA_HISTOGRAM_TIMER("Media.AudioOutputController.PauseTime");
 
   StopStream();
 
   if (state_ != kPaused)
     return;
 
-  // Send a special pause mark to the low-latency audio thread.
-  sync_reader_->UpdatePendingBytes(kPauseMark);
+  // Let the renderer know we've stopped.  Necessary to let PPAPI clients know
+  // audio has been shutdown.  TODO(dalecurtis): This stinks.  PPAPI should have
+  // a better way to know when it should exit PPB_Audio_Shared::Run().
+  sync_reader_->UpdatePendingBytes(-1);
 
 #if defined(AUDIO_POWER_MONITORING)
   // Paused means silence follows.
   handler_->OnPowerMeasured(AudioPowerMonitor::zero_power(), false);
 #endif
 
   handler_->OnPaused();
 }
 
 void AudioOutputController::DoClose() {
@@ skipping 35 matching lines @@
                                       AudioBuffersState buffers_state) {
   return OnMoreIOData(NULL, dest, buffers_state);
 }
 
 int AudioOutputController::OnMoreIOData(AudioBus* source,
                                         AudioBus* dest,
                                         AudioBuffersState buffers_state) {
   DisallowEntryToOnMoreIOData();
   TRACE_EVENT0("audio", "AudioOutputController::OnMoreIOData");
 
-  // The OS level audio APIs on Linux and Windows all have problems requesting
-  // data on a fixed interval.  Sometimes they will issue calls back to back
-  // which can cause glitching, so wait until the renderer is ready.
-  //
-  // We also need to wait when diverting since the virtual stream will call this
-  // multiple times without waiting.
-  //
-  // NEVER wait on OSX unless a virtual stream is connected, otherwise we can
-  // end up hanging the entire OS.
-  //
-  // See many bugs for context behind this decision: http://crbug.com/170498,
-  // http://crbug.com/171651, http://crbug.com/174985, and more.
-#if defined(OS_WIN) || defined(OS_LINUX)
-    const bool kShouldBlock = true;
-#else
-    const bool kShouldBlock = diverting_to_stream_ != NULL;
-#endif
+  sync_reader_->Read(source, dest);
 
-  const int frames = sync_reader_->Read(kShouldBlock, source, dest);
-  DCHECK_LE(0, frames);
+  const int frames = dest->frames();
   sync_reader_->UpdatePendingBytes(
       buffers_state.total_bytes() + frames * params_.GetBytesPerFrame());
 
 #if defined(AUDIO_POWER_MONITORING)
   power_monitor_.Scan(*dest, frames);
 #endif
 
   AllowEntryToOnMoreIOData();
   return frames;
 }
@@ skipping 99 matching lines @@
   DCHECK(base::AtomicRefCountIsZero(&num_allowed_io_));
   base::AtomicRefCountInc(&num_allowed_io_);
 }
 
 void AudioOutputController::DisallowEntryToOnMoreIOData() {
   const bool is_zero = !base::AtomicRefCountDec(&num_allowed_io_);
   DCHECK(is_zero);
 }
 
 }  // namespace media