RenderSharedTimerDriven

This sample application uses the Core Audio APIs to render audio data to an output device specified by the user. This sample demonstrates timer-driven buffering for a rendering client in shared mode. For a shared-mode stream, the client shares the endpoint buffer with the audio engine.

This topic contains the following sections.

Description

This sample demonstrates the following features.

  • MMDevice API for multimedia device enumeration and selection.
  • WASAPI for stream management operations.

Requirements

ProductVersion
Windows SDKWindows 7
Visual Studio2008

 

Downloading the Sample

This sample is available in the following locations.

LocationPath/URL
Windows SDK\Program Files\Microsoft SDKs\Windows\v7.0\Samples\Multimedia\Audio\RenderSharedTimerDriven\...

 

Building the Sample

To build the RenderSharedTimerDriven sample, use the following steps:

  1. Open the CMD shell for the Windows SDK and change to the RenderSharedTimerDriven sample directory.
  2. Run the command start WASAPIRenderSharedTimerDriven.sln in the RenderSharedTimerDriven directory to open the WASAPIRenderSharedTimerDriven project in the Visual Studio window.
  3. From within the window, select the Debug or Release solution configuration, select the Build menu from the menu bar, and select the Build option. If you do not open Visual Studio from the CMD shell for the SDK, Visual Studio will not have access to the SDK build environment. In that case, the sample will not build unless you explicitly set environment variable MSSdk, which is used in the project file, WASAPIRenderSharedTimerDriven.vcproj.

Running the Sample

If you build the demo application successfully, an executable file, WASAPIRenderSharedTimerDriven.exe, is generated. To run it, type WASAPIRenderSharedTimerDriven in a command window followed by required or optional arguments. The following example shows how to run the sample by specifying playback duration on the default multimedia device.

WASAPIRenderSharedTimerDriven.exe -d 20 -multimedia

The following table shows the arguments.

ArgumentDescription
-? Shows help.
-h Shows help.
-fSine wave frequency in Hz.
-l Audio render latency in milliseconds.
-d Sine wave duration in seconds.
-mDisables the use of MMCSS.
-consoleUse the default console device.
-communicationsUse the default communication device.
-multimediaUse the default multimedia device.
-endpoint Use the endpoint identifier specified in the switch value.

 

If the application is run without arguments, it enumerates the available devices and prompts the user to select a device for the rendering session. After the user specifies a device, the application renders a sine wave at 440 Hz for 10 seconds. These values can be modified by specifying -f and -d switch values.

RenderSharedTimerDriven demonstrates timer-driven buffering. In this mode, the client must wait for a period of time (half the latency, specified by the -d switch value, in milliseconds). When the client wakes up, half way through the processing period, it pulls the next set of samples from the engine. Before each processing pass in the buffering loop, the client must find out the amount of data to render so that the data does not overrun the buffer.

Audio data to be played on the specified device can be processed by enabling event-driven buffering. This mode is demonstrated in the RenderSharedEventDriven sample.

For more information about rendering a stream, see Rendering a Stream.

Related topics

SDK Samples That Use the Core Audio APIs

 

 

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