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Osprey-300 User’s Guide
Preview Pin to VMR7
VMR7 is short for “Video Mixing Renderer 7”. VMR7 is a newer renderer that is generally much faster
than the old Video Renderer. It uses an efficient DirectDraw configuration to render with almost no cpu
overhead, so long as the correct video format is used.
Unfortunately, VMR7 is not the default video renderer in building a filtergraph – an application must
explicitly ask for VMR7 in its graph in order for it to be used. This causes many older or quick-and-dirty
applications to render video much less efficiently than they might.
VMR7 will work about equally well with either the YUY2 video format, or with the RGB format – RGB32,
or RGB555 – that matches the current screen depth. Since YUY2 uses less PCI bandwidth (2 bytes per
pixel) than RGB24 or RGB32 (3 or 4 bytes per pixel), it is the best choice. We recommend, though, letting
DirectShow choose the video format. It will generally make the correct choice. Also, if two video frames
are to be rendered with VMR7 at the same time, only one can be YUY2; other(s) will be RGB.
We do not provide an RGB24 option for use with 24-bit screens because on at least some display adapters
the rendering of RGB24 to VMR7 is incorrect.
It is important to note that VMR7 cannot be used when closed captions must be rendered – use the Overlay
Mixer to Video Renderer pathway instead.
Preview Pin to VMR9
Video Mixing Renderer 9 is the newest video rendering method and the one on which Microsoft will base its
future development. The intent is to combine the functionality of the Overlay Mixer plus Video Renderer
in one module that takes advantage of the latest developments in DirectShow. We are finding that at its
present stage of development, with our hardware, VMR9 does not achieve the very high efficiency of YUY2-
to-VMR7, but its overall performance is consistently quite good.
One specific problem: VMR9 at present does not currently render closed captioning correctly, at least on
our particular test machines. Although it is possible to connect the output of the Line 21 Decoder to a
VMR9 input, the captions will not be positioned or displayed correctly.
Summary of Contents for Osprey-300
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