ViewCast Osprey PCI, User Manual

Page: 84 / 126

AVStream Driver Reference Information
78 ViewCast
Preview Pin to VMR7
Figure 56. 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. 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 in order for it to be used. This causes many simpler applications
to render video much less efficiently than they might.
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 will generally make 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) will be 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 will work and is recommended.