Modified Windows buffer size to avoid audio glitches.

remoting/host/audio_capturer_win.cc

Index: remoting/host/audio_capturer_win.cc
diff --git a/remoting/host/audio_capturer_win.cc b/remoting/host/audio_capturer_win.cc
index b450a9a543e770582de73cfc94e0c95800b49e33..ce4c5f7c42da4ea34beaf3628eedfaff8260aa31 100644
--- a/remoting/host/audio_capturer_win.cc
+++ b/remoting/host/audio_capturer_win.cc
@@ -34,6 +34,11 @@ const int kHnsToMs = 10000;
 // silence. A value of 2 was chosen, because Windows can give samples of 1 and
 // -1, even when no audio is playing.
 const int kSilenceThreshold = 2;
+
+// Number of packets that can be stored in the Windows capture buffer.
+// Even if we capture once every |audio_device_period_| * |kWindowsBufferSize|,
+// we will buffer enough to avoid glitches.
+const int kWindowsBufferSize = 10;

[Wez, 2012/08/15 21:32:29]

Why 10? Surely we want to configure things to cope with some maximum
timer-triggering latency, rather than a fixed multiplier of the audio capture
period, which is device-specific?

e.g. If we know we can only do 10ms granularity timers, but that we might see
bursts of 30ms latency between timers, and Windows reports a 5ms audio sample
period then we want 6x buffers.

[kxing, 2012/08/16 17:30:57]

Done.

 }  // namespace
 
 namespace remoting {
@@ -195,7 +200,7 @@ bool AudioCapturerWin::Start(const PacketCapturedCallback& callback) {
   // Initialize the IAudioClient.
   hr = audio_client_->Initialize(AUDCLNT_SHAREMODE_SHARED,
                                  AUDCLNT_STREAMFLAGS_LOOPBACK,
-                                 0,
+                                 device_period * kWindowsBufferSize,

[Sergey Ulanov, 2012/08/15 21:43:22]

Does this have to be multiple of device_period? Can we just specify the double
of the desired latency. E.g. we could have the buffer allocated for 100ms and
then schedule the timer to pull the data from the buffer every 50ms. That will
also give us enough room in the buffer to cope with timer volatility.

[kxing, 2012/08/16 17:30:57]

Done.

                                  0,
                                  wave_format_ex_,
                                  NULL);