Low-latency AudioInputStream implementation based on WASAPI for Windows.

media/audio/audio_util.cc

 // Copyright (c) 2011 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.
 
 // Software adjust volume of samples, allows each audio stream its own
 // volume without impacting master volume for chrome and other applications.
 
 // Implemented as templates to allow 8, 16 and 32 bit implementations.
 // 8 bit is unsigned and biased by 128.
 
 #include <algorithm>
 
 #include "base/atomicops.h"
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/shared_memory.h"
+#if defined(OS_WIN)
+#include "base/win/windows_version.h"
+#endif
 #include "media/audio/audio_util.h"
 #if defined(OS_MACOSX)
+#include "media/audio/mac/audio_low_latency_input_mac.h"
 #include "media/audio/mac/audio_low_latency_output_mac.h"
 #endif
+#if defined(OS_WIN)
+#include "media/audio/win/audio_low_latency_input_win.h"
+#endif
 
 using base::subtle::Atomic32;
 
 const uint32 kUnknownDataSize = static_cast<uint32>(-1);
 
 namespace media {
 
 // TODO(fbarchard): Convert to intrinsics for better efficiency.
 template<class Fixed>
 static int ScaleChannel(int channel, int volume) {
@@ skipping 192 matching lines @@
       if (sample < -32768.0)
         sample = -32768.0;
       else if (sample > 32767.0)
         sample = 32767.0;
 
       destination[j * channels + i] = static_cast<int16>(sample);
     }
   }
 }
 
-double GetAudioHardwareSampleRate()
-{
+double GetAudioHardwareSampleRate() {
 #if defined(OS_MACOSX)
     // Hardware sample-rate on the Mac can be configured, so we must query.
     return AUAudioOutputStream::HardwareSampleRate();
 #else
     // Hardware for Windows and Linux is nearly always 48KHz.
     // TODO(crogers) : return correct value in rare non-48KHz cases.
     return 48000.0;
 #endif
 }
 
+double GetAudioInputHardwareSampleRate() {
+#if defined(OS_MACOSX)
+  // Hardware sample-rate on the Mac can be configured, so we must query.
+  return AUAudioInputStream::HardwareSampleRate();
+#elif defined(OS_WIN)
+  if (base::win::GetVersion() <= base::win::VERSION_XP) {
+    // Fall back to Windows Wave implementation on Windows XP or lower
+    // and use 48kHz as default input sample rate.
+    return 48000.0;
+  } else {
+    // Hardware sample-rate on Windows can be configured, so we must query.
+    // TODO(henrika): improve possibility to specify audio endpoint.
+    // Use the default device (same as for Wave) for now to be compatible.
+    return WASAPIAudioInputStream::HardwareSampleRate(eConsole);
+  }
+#else
+  // Hardware for Linux is nearly always 48KHz.
+  // TODO(henrika) : return correct value in rare non-48KHz cases.

[scherkus (not reviewing), 2011/10/18 21:12:30]

nit: remove space between ) and :

[henrika (OOO until Aug 14), 2011/10/19 15:42:43]

Done.

+  return 48000.0;
+#endif
+}
+
 size_t GetAudioHardwareBufferSize() {
   // The sizes here were determined by experimentation and are roughly
   // the lowest value (for low latency) that still allowed glitch-free
   // audio under high loads.
   //
   // For Mac OS X the chromium audio backend uses a low-latency
   // CoreAudio API, so a low buffer size is possible.  For other OSes,
   // further tuning may be needed.
 #if defined(OS_MACOSX)
   return 128;
@@ skipping 48 matching lines @@
   char* ptr = static_cast<char*>(shared_memory->memory()) + shared_memory_size;
   DCHECK_EQ(0u, reinterpret_cast<size_t>(ptr) & 3);
 
   // Actual data size stored at the end of the buffer.
   uint32 actual_data_size =
       base::subtle::Acquire_Load(reinterpret_cast<volatile Atomic32*>(ptr));
   return actual_data_size == kUnknownDataSize;
 }
 
 }  // namespace media