Adding experimental exclusive-mode streaming to WASAPIAudioOutputStream

media/audio/audio_util.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.
 
 // 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.
 
 // TODO(vrk): This file has been running pretty wild and free, and it's likely
 // that a lot of the functions can be simplified and made more elegant. Revisit
 // after other audio cleanup is done. (crbug.com/120319)
 
 #include <algorithm>
 #include <limits>
 
 #include "base/atomicops.h"
 #include "base/basictypes.h"
 #include "base/logging.h"
 #include "base/shared_memory.h"
 #include "base/time.h"
-#if defined(OS_WIN)
-#include "base/sys_info.h"
-#include "base/win/windows_version.h"
-#include "media/audio/audio_manager_base.h"
-#endif
 #include "media/audio/audio_parameters.h"
 #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)
+#elif defined(OS_WIN)
+#include "base/command_line.h"
+#include "base/sys_info.h"
+#include "base/win/windows_version.h"
 #include "media/audio/win/audio_low_latency_input_win.h"
 #include "media/audio/win/audio_low_latency_output_win.h"
+#include "media/base/media_switches.h"
+#include "media/audio/audio_manager_base.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>
@@ skipping 297 matching lines @@
 #if defined(OS_MACOSX)
   // Hardware sample-rate on the Mac can be configured, so we must query.
   return AUAudioOutputStream::HardwareSampleRate();
 #elif defined(OS_WIN)
   if (!IsWASAPISupported()) {
     // Fall back to Windows Wave implementation on Windows XP or lower
     // and use 48kHz as default input sample rate.
     return 48000;
   }
 
-  // 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 WASAPIAudioOutputStream::HardwareSampleRate(eConsole);
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  if (!cmd_line->HasSwitch(switches::kEnableExclusiveMode)) {

[scherkus (not reviewing), 2012/06/28 00:04:41]

doh rietveld swallowed my comment from the last PS :(

I was going to say it smells a bit funny that we have a few bits + pieces of
switch-checking code here. Ideally we isolate all changes that require this flag
in one spot and be done with it. In particular, this code is relying on
AudioManagerWin to be doing its job creating exclusive WASAPIAOS objects.

I don't think there's much we can fix in the short term. Longer term I think
what we actually want is to most of this file moved into the OS-specific
AudioManager implementations. That way we could create an AudioManagerWin impl
that knows it's working in exclusive mode and as such isolate all the
exclusive-mode code but alas we'll have to save that for another time :)

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Point taken. Will improve in an upcoming version.

+    // 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 WASAPIAudioOutputStream::HardwareSampleRate(eConsole);

[scherkus (not reviewing), 2012/06/28 00:04:41]

I also noticed that all current usage for E_ROLE is eConsole. Do we have plans
to remove this argument at some point and perhaps make it a constant inside the
WASAPI .cc?

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

It is not so simple to fix. We have a better solution today on the input side
where I have added support for proper device selection. This parameter is then
replaced by a const std::string& device_id. There has so far not been any
requests for selection of (other than default device) on the output side. Hmmm,
given this fact, it might in fact be better to hide eConsole as you propose.
Improving the TODO comment.

+  } else {
+    return 44100;

[scherkus (not reviewing), 2012/06/28 00:04:41]

where is 44100 coming from?

for example we seem to use 48000 on other branches -- some docs would be nice

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Rewrote this section and added new comments to make it more clear.

+  }
 #elif defined(OS_ANDROID)
   return 16000;
 #else
     // Hardware for Linux is nearly always 48KHz.
     // TODO(crogers) : return correct value in rare non-48KHz cases.
     return 48000;

[scherkus (not reviewing), 2012/06/28 00:04:41]

nit: can you fix indent here?

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Done.

 #endif
 }
 
 int GetAudioInputHardwareSampleRate(const std::string& device_id) {
   // TODO(henrika): add support for device selection on all platforms.
   // Only exists on Windows today.
 #if defined(OS_MACOSX)
   return AUAudioInputStream::HardwareSampleRate();
 #elif defined(OS_WIN)
   if (!IsWASAPISupported()) {
@@ skipping 16 matching lines @@
   // Core Audio API, so a low buffer size is possible. For Linux, further
   // tuning may be needed.
 #if defined(OS_MACOSX)
   return 128;
 #elif defined(OS_WIN)
   if (!IsWASAPISupported()) {
     // Fall back to Windows Wave implementation on Windows XP or lower
     // and assume 48kHz as default sample rate.
     return 2048;
   }
+
+  // TODO(croger): tune this size to best possible WebAudio performance.

[scherkus (not reviewing), 2012/06/28 00:04:41]

s/croger/crogers

[henrika (OOO until Aug 14), 2012/07/25 11:18:22]

Done.

+  // WebRTC always uses 480 for Windows and does not call this method.
+  // Note that exclusive mode is experimental.
+  const CommandLine* cmd_line = CommandLine::ForCurrentProcess();
+  if (cmd_line->HasSwitch(switches::kEnableExclusiveMode)) {
+    return 256;
+  }
+
   // This call must be done on a COM thread configured as MTA.
   // TODO(tommi): http://code.google.com/p/chromium/issues/detail?id=103835.
   int mixing_sample_rate =
       WASAPIAudioOutputStream::HardwareSampleRate(eConsole);
   if (mixing_sample_rate == 48000)
     return 480;
   else if (mixing_sample_rate == 44100)
     return 448;
   else
     return 960;
@@ skipping 120 matching lines @@
   if ((base::SysInfo::NumberOfProcessors() < 2) ||
       (base::win::GetVersion() == base::win::VERSION_VISTA)) {
     return 3;
   }
   return 2;
 }
 
 #endif
 
 }  // namespace media