IWMStreamConfig::SetBufferWindow method (wmsdkidl.h)

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4/26/2023

[The feature associated with this page, Windows Media Format 11 SDK, is a legacy feature. It has been superseded by Source Reader and Sink Writer. Source Reader and Sink Writer have been optimized for Windows 10 and Windows 11. Microsoft strongly recommends that new code use Source Reader and Sink Writer instead of Windows Media Format 11 SDK, when possible. Microsoft suggests that existing code that uses the legacy APIs be rewritten to use the new APIs if possible.]

The SetBufferWindow method specifies the maximum latency between when a stream is received and when it begins to be displayed.

Syntax

HRESULT SetBufferWindow(
  [in] DWORD msBufferWindow
);

Parameters

[in] msBufferWindow

Buffer window, in milliseconds.

Return value

This method always returns S_OK.

Remarks

For high bit rate streams (typically, more than 1 megabit per second), a latency (or buffer window) of 1 second is typical; for lower bit rate streams, a latency of approximately 3 seconds is often used.

Setting the buffer window to -1 (0xFFFFFFFF) indicates that the buffer window is unknown. In this case, the writer selects the buffer window size.

For video streams, a larger buffer window gives higher quality.

Note A problem can arise if you create a file containing streams with widely varying buffer windows. Playback applications created with a previous version of the Windows Media Format SDK have difficulty rendering the data from such files properly. If you are creating files to be used with older players, you should ensure that the buffer windows of any two streams do not vary by more than five seconds.

The new value will not take effect in the profile until you call IWMProfile::ReconfigStream.

Requirements

Requirement	Value
Minimum supported client	Windows 2000 Professional [desktop apps only],Windows Media Format 7 SDK, or later versions of the SDK
Minimum supported server	Windows 2000 Server [desktop apps only]
Target Platform	Windows
Header	wmsdkidl.h (include Wmsdk.h)
Library	Wmvcore.lib; WMStubDRM.lib (if you use DRM)

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