IsVBR
[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 It has been superseded by Source Reader and Sink Writer.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 IsVBR attribute specifies whether the content in a stream was encoded using variable bit rate (VBR) encoding.
g_wszWMIsVBR
WMT_TYPE_BOOL
When accessing the IWMHeaderInfo3 interface of the writer object, you can add or change this value. In other objects (metadata editor, reader, and synchronous reader), this value is read-only.