Rastergraf Topaz, User Manual

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Rastergraf
1-14 General Information
The display controller implements independent capture and playback
subsystems. The capture system receives digitized video data through its
16 bit Video Input Port, which is driven by a multiplexer that selects
between the on-board Bt835 NTSC/PAL video decoder (see
Section 1.4 )
and the AD9882 RGBHV/DVI decoder (see Section 1.5 ). It places it in a
capture buffer in display memory. The playback system retrieves the video
data from the buffer and inserts it into a window in the display stream
(screen image). The output display resolution and timing is not related to
the incoming video resolution and timing so live interlaced video input
may be incorporated into the graphics display without introducing video-
related artifacts.
Figure 1-9 Capture Buffer and Display Memory
Video Playback
Once the incoming digitized video data has been placed into the capture
buffer, the playback engine can retrieve it and incorporate it into the
display output stream. The playback engine can up-scale (zoom) the
contents of the video capture buffer before incorporating the capture
image into the output stream. The image may either be made to fill the
entire screen at the current resolution, or occupy a “window” within the
larger output display. The window may be of arbitrary size and located on
any pixel boundary. Color keying may be used to create non-rectangular
windows, and/or to superimpose a graphics overlay on the video image.
Video Image
(Input)
Source
Rectangle
Crop
&
Scale
Capture
Buffer
Scale
&
Pan
Screen Display
(Output)
Display
Memory
Video
Window