Index: media/audio/win/audio_low_latency_output_win.h |
diff --git a/media/audio/win/audio_low_latency_output_win.h b/media/audio/win/audio_low_latency_output_win.h |
index 67a5d6c5f0a2c496c6e8828815110ac06f3ad202..a3136a9c271eccf358b235fd642bfb0d0f5e68f6 100644 |
--- a/media/audio/win/audio_low_latency_output_win.h |
+++ b/media/audio/win/audio_low_latency_output_win.h |
@@ -112,6 +112,29 @@ |
// - All callback methods from the IMMNotificationClient interface will be |
// called on a Windows-internal MMDevice thread. |
// |
+// Experimental exclusive mode: |
+// |
+// - It is possible to open up a stream in exclusive mode by using the |
+// "--enable-exclusive-mode" command-line flag. |
scherkus (not reviewing)
2012/07/25 23:44:44
ditch ""s on the flag
henrika (OOO until Aug 14)
2012/07/26 08:31:11
Done.
|
+// - The internal buffering scheme is less flexible for exclusive-mode streams. |
+// Hence, some manual tuning will be required before deciding what frame |
+// size to use. See the WinAudioOutputTest unit test for more details. |
+// - If an application opens a stream in exclusive mode, the application has |
+// exclusive use of the audio endpoint device that plays the stream. |
+// - Exclusive-mode access to an audio device can block system sounds, prevent |
+// interoperability with other applications, and otherwise degrade the user |
+// experience. |
+// - Exclusive-mode should only be utilized when the lowest possible latency |
+// is important. |
+// - In exclusive mode, the client can choose to open the stream in any audio |
+// format that the endpoint device supports. |
+// - Initial measurements on Windows 7 have shown that the lowest possible |
+// latencies we can achieve are: |
+// o ~3.3333ms @ 48kHz <=> 160 audio frames per buffer. |
+// o ~3.6281ms @ 44.1kHz <=> 160 audio frames per buffer. |
+// - See http://msdn.microsoft.com/en-us/library/windows/desktop/dd370844(v=vs.85).aspx |
+// for more details. |
+ |
#ifndef MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_OUTPUT_WIN_H_ |
#define MEDIA_AUDIO_WIN_AUDIO_LOW_LATENCY_OUTPUT_WIN_H_ |
@@ -163,11 +186,16 @@ class MEDIA_EXPORT WASAPIAudioOutputStream |
// Retrieves the stream format that the audio engine uses for its internal |
// processing/mixing of shared-mode streams. |
+ // This method should not be used in combination with exclusive-mode streams. |
static int HardwareSampleRate(ERole device_role); |
bool started() const { return started_; } |
private: |
+ // Returns AUDCLNT_SHAREMODE_EXCLUSIVE if "enable-exclusive-mode" is used |
scherkus (not reviewing)
2012/07/25 23:44:44
ditch ""s and just use --enable-exclusive-mode
henrika (OOO until Aug 14)
2012/07/26 08:31:11
Done.
|
+ // as command-line flag and AUDCLNT_SHAREMODE_SHARED otherwise (default). |
+ static AUDCLNT_SHAREMODE GetShareMode(); |
+ |
// Implementation of IUnknown (trivial in this case). See |
// msdn.microsoft.com/en-us/library/windows/desktop/dd371403(v=vs.85).aspx |
// for details regarding why proper implementations of AddRef(), Release() |
@@ -206,12 +234,20 @@ class MEDIA_EXPORT WASAPIAudioOutputStream |
void HandleError(HRESULT err); |
// The Open() method is divided into these sub methods. |
- HRESULT SetRenderDevice(ERole device_role); |
+ HRESULT SetRenderDevice(); |
HRESULT ActivateRenderDevice(); |
HRESULT GetAudioEngineStreamFormat(); |
bool DesiredFormatIsSupported(); |
HRESULT InitializeAudioEngine(); |
+ // Called when the device will be opened in shared mode and use the WAS |
scherkus (not reviewing)
2012/07/25 23:44:44
WAS?
henrika (OOO until Aug 14)
2012/07/26 08:31:11
Modified.
|
+ // format. |
+ HRESULT SharedModeInitialization(); |
+ |
+ // Called when the device will be opened in exclusive mode and use the |
+ // application specified format. |
+ HRESULT ExclusiveModeInitialization(); |
+ |
// Converts unique endpoint ID to user-friendly device name. |
std::string GetDeviceName(LPCWSTR device_id) const; |
@@ -222,6 +258,8 @@ class MEDIA_EXPORT WASAPIAudioOutputStream |
// new default audio device. |
bool RestartRenderingUsingNewDefaultDevice(); |
+ AUDCLNT_SHAREMODE share_mode() const { return share_mode_; } |
+ |
// Initializes the COM library for use by the calling thread and sets the |
// thread's concurrency model to multi-threaded. |
base::win::ScopedCOMInitializer com_init_; |
@@ -276,6 +314,11 @@ class MEDIA_EXPORT WASAPIAudioOutputStream |
// Defines the role that the system has assigned to an audio endpoint device. |
ERole device_role_; |
+ // The sharing mode for the connection. |
+ // Valid values are AUDCLNT_SHAREMODE_SHARED and AUDCLNT_SHAREMODE_EXCLUSIVE |
+ // where AUDCLNT_SHAREMODE_SHARED is the default. |
+ AUDCLNT_SHAREMODE share_mode_; |
+ |
// Counts the number of audio frames written to the endpoint buffer. |
UINT64 num_written_frames_; |