Enable higher latency audio on Windows for basic playback.

media/base/audio_hardware_config.cc

Index: media/base/audio_hardware_config.cc
diff --git a/media/base/audio_hardware_config.cc b/media/base/audio_hardware_config.cc
index 65506ca8f05e144ddd4ca4eb2bdd0cce56eac103..d00e03f6b089334b19be067c96d6445ace1585d6 100644
--- a/media/base/audio_hardware_config.cc
+++ b/media/base/audio_hardware_config.cc
@@ -5,6 +5,7 @@
 #include "media/base/audio_hardware_config.h"
 
 #include <algorithm>
+#include <cmath>
 
 #include "base/logging.h"
 #include "build/build_config.h"
@@ -14,11 +15,7 @@ using media::AudioParameters;
 
 namespace media {
 
-#if defined(OS_LINUX) || defined(OS_MACOSX)
-#define HIGH_LATENCY_AUDIO_SUPPORT 1
-#endif
-
-#if defined(HIGH_LATENCY_AUDIO_SUPPORT)
+#if !defined(OS_WIN)
 // Taken from "Bit Twiddling Hacks"
 // http://graphics.stanford.edu/~seander/bithacks.html#RoundUpPowerOf2
 static uint32_t RoundUpToPowerOfTwo(uint32_t v) {
@@ -102,9 +99,19 @@ void AudioHardwareConfig::UpdateOutputConfig(
 
 int AudioHardwareConfig::GetHighLatencyBufferSize() const {
   AutoLock auto_lock(config_lock_);
-#if defined(HIGH_LATENCY_AUDIO_SUPPORT)
-  // Empirically, use the nearest higher power of two buffer size corresponding
-  // to 20 ms worth of samples.  For a given sample rate, this works out to:
+
+  // Empirically, we consider 20ms of samples to be high latency.
+  const double twenty_ms_size = 2.0 * output_params_.sample_rate() / 100;
+
+#if defined(OS_WIN)
+  // Windows doesn't use power of two buffer sizes, so we should always round up
+  // to the nearest multiple of the output buffer size.
+  const int high_latency_buffer_size =
+      std::ceil(twenty_ms_size / output_params_.frames_per_buffer()) *
+      output_params_.frames_per_buffer();
+#else
+  // On other platforms use the nearest higher power of two buffer size.  For a
+  // given sample rate, this works out to:
   //
   //     <= 3200   : 64
   //     <= 6400   : 128
@@ -115,14 +122,11 @@ int AudioHardwareConfig::GetHighLatencyBufferSize() const {
   //     <= 204800 : 4096
   //
   // On Linux, the minimum hardware buffer size is 512, so the lower calculated
-  // values are unused.  OSX may have a value as low as 128.  Windows is device
-  // dependent but will generally be sample_rate() / 100.
-  const int high_latency_buffer_size =
-      RoundUpToPowerOfTwo(2 * output_params_.sample_rate() / 100);
+  // values are unused.  OSX may have a value as low as 128.
+  const int high_latency_buffer_size = RoundUpToPowerOfTwo(twenty_ms_size);
+#endif  // defined(OS_WIN)
+
   return std::max(output_params_.frames_per_buffer(), high_latency_buffer_size);
-#else
-  return output_params_.frames_per_buffer();
-#endif
 }
 
 }  // namespace media