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Chapter 6: Video Driver Topics
Preview Pin to Video Renderer
This is the oldest, simplest, and usually least efficient way of rendering video. It does not use DirectDraw
in the rendering process. It is the default rendering pathway that will be chosen when an application says
“Render” without specifying a preferred pathway. For this reason, many applications, especially older ones,
deliver unnecessarily poor rendering performance.
The fastest video format to use with this pathway is whatever RGB format corresponds to your screen
depth – RGB32 for a 32-bit screen, or RGB555 for a 16-bit screen. But it is even better to avoid using this
pathway altogether.
Preview Pin to Overlay Mixer to Video Renderer
The combination of Overlay Mixer plus Video Renderer provides much better performance than a direct
connection of Preview Pin to Video Renderer.
At present this is the only pathway that renders closed captioning correctly. For CC rendering, the output of
the Line 21 filter connects to an input of the Overlay Mixer.
A curious illustration of the effect of the Overlay Mixer is seen with AMCap, a Microsoft DirectShow
reference application that is available in object and source form. If the application is configured to preview
at a full 720x480, with closed captioning turned off, the cpu will be swamped and on a slow machine
the video will be jerky. In this case it uses the direct Preview Pin to Video Renderer pathway. If closed
captioning is turned on, AMCap adds Overlay Mixer to the rendering pathway, and cpu utilization drops to 25
percent of what it was, and the video is perfectly smooth.
The best video format to use with Overlay Mixer is YUY2.
Summary of Contents for Osprey-300
Page 1: ...Osprey 300 User s Guide...
