IAudioRenderClient::ReleaseBuffer method (audioclient.h)

The ReleaseBuffer method releases the buffer space acquired in the previous call to the IAudioRenderClient::GetBuffer method.


HRESULT ReleaseBuffer(
  [in] UINT32 NumFramesWritten,
  [in] DWORD  dwFlags


[in] NumFramesWritten

The number of audio frames written by the client to the data packet. The value of this parameter must be less than or equal to the size of the data packet, as specified in the NumFramesRequested parameter passed to the IAudioRenderClient::GetBuffer method.

[in] dwFlags

The buffer-configuration flags. The caller can set this parameter either to 0 or to the following _AUDCLNT_BUFFERFLAGS enumeration value (a flag bit):


If this flag bit is set, the audio engine treats the data packet as though it contains silence regardless of the data values contained in the packet. This flag eliminates the need for the client to explicitly write silence data to the rendering buffer.

Return value

If the method succeeds, it returns S_OK. If it fails, possible return codes include, but are not limited to, the values shown in the following table.

Return code Description
The NumFramesWritten value exceeds the NumFramesRequested value specified in the previous IAudioRenderClient::GetBuffer call.
The stream is exclusive mode and uses event-driven buffering, but the client attempted to release a packet that was not the size of the buffer.
This call was not preceded by a corresponding call to IAudioRenderClient::GetBuffer.
The audio endpoint device has been unplugged, or the audio hardware or associated hardware resources have been reconfigured, disabled, removed, or otherwise made unavailable for use.
The Windows audio service is not running.
Parameter dwFlags is not a valid value.


The client must release the same number of frames that it requested in the preceding call to the IAudioRenderClient::GetBuffer method. The single exception to this rule is that the client can always call ReleaseBuffer to release 0 frames (unless the stream is exclusive mode and uses event-driven buffering).

This behavior provides a convenient means for the client to "release" a previously requested packet of length 0. In this case, the call to ReleaseBuffer is optional. After calling GetBuffer to obtain a packet of length 0, the client has the option of not calling ReleaseBuffer before calling GetBuffer again.

In addition, if the preceding GetBuffer call obtained a packet of nonzero size, calling ReleaseBuffer with NumFramesRequested set to 0 will succeed (unless the stream is exclusive mode and uses event-driven buffering). The meaning of the call is that the client wrote no data to the packet before releasing it. Thus, the method treats the portion of the buffer represented by the packet as unused and will make this portion of the buffer available again to the client in the next GetBuffer call.

Clients should avoid excessive delays between the GetBuffer call that acquires a buffer and the ReleaseBuffer call that releases the buffer. The implementation of the audio engine assumes that the GetBuffer call and the corresponding ReleaseBuffer call occur within the same buffer-processing period. Clients that delay releasing a buffer for more than one period risk losing sample data.

For code examples that call the ReleaseBuffer method, see the following topics:


Requirement Value
Minimum supported client Windows Vista [desktop apps | UWP apps]
Minimum supported server Windows Server 2008 [desktop apps | UWP apps]
Target Platform Windows
Header audioclient.h

See also


IAudioRenderClient Interface