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.
- Downloading the Sample
- Building the Sample
- Running the Sample
- Related topics
This sample demonstrates the following features.
- MMDevice API for multimedia device enumeration and selection.
- WASAPI for stream management operations.
|Windows SDK||Windows 7|
Downloading the Sample
This sample is available in the following locations.
|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:
- Open the CMD shell for the Windows SDK and change to the RenderSharedTimerDriven sample directory.
- Run the command
start WASAPIRenderSharedTimerDriven.slnin the RenderSharedTimerDriven directory to open the WASAPIRenderSharedTimerDriven project in the Visual Studio window.
- 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.
|-f||Sine wave frequency in Hz.|
|-l||Audio render latency in milliseconds.|
|-d||Sine wave duration in seconds.|
|-m||Disables the use of MMCSS.|
|-console||Use the default console device.|
|-communications||Use the default communication device.|
|-multimedia||Use 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.