Computer Drive User Manual

AVStream Driver Reference Information
72 ViewCast
Preview Pin to VMR7
Figure 65. Video Mixing Renderer 7
VMR7 is short for Video Mixing Renderer 7. VMR7 is a newer renderer that is generally much faster than
the old Video Renderer. When the driver is running in Direct Mode, VMR7 uses an efficient DirectDraw
configuration to render with almost no CPU overhead, especially when YUY2 video is used. When the
driver is running in PostProcessing Mode, DirectDraw is not used but it is still the fastest renderer.
Unfortunately, VMR7 is not the default video renderer in building a filtergraph – an application must
explicitly ask for VMR7 in its graph for it to be used. This process causes many simpler applications to
render video much less efficiently.
VMR7 works best with YUY2 video and there is usually little reason to use any other format. It will,
however, work fairly well with the RGB format – usually RGB32 – that matches the current screen depth.
We recommend letting DirectShow choose the video format. It generally makes the correct choice. In
particular, on some (usually older) systems, if two video frames are to be rendered with VMR7 at the
same time, only one can be YUY2; other(s) are RGB, with a conversion filter inserted into the graph if
necessary.
We do not provide an RGB24 option on the preview pin for use with 24-bit screens because on at least
some display adapters the rendering of RGB24 to VMR7 is incorrect.
Note: VMR7 cannot be used when closed captions are to be rendered from the driver’s DShow-
standard CC or VBI pin – use the Overlay Mixer to Video Renderer pathway instead. If the
driver’s internal rendering is used, the VMR7 works and is recommended.