RIVA128ZX Datasheet, PDF (44/85 Pages) STMicroelectronics – 128-BIT 3D MULTIMEDIA ACCELERATOR

RIVA128ZX
Figure 44. Displaying 2 fields with 1:1 ratio
Frame 1 (Top field)
Line 11
Interpolated line
(Line 11 & 13)
Line 13
128-BIT 3D MULTIMEDIA ACCELERATOR
Frame 2 (Bottom field)
Line 10
Interpolated line
(Line 10 & 12)
Line 12
The RIVA128ZX video overlay handles interlaced
video by displaying every field, at the original frame
rate of the video (50Hz for PAL and 60Hz for
NTSC). The video scaling logic upscales, in the ver-
tical direction, the luma components in each field
and linearly interpolates successive lines to pro-
duce the missing lines of each field. This interpolat-
ed scale is applied such that the full frame size of
each field is stretched to the desired height.
The video scaler offsets the bottom field image by
half a source image line to ensure that both frames
when played back align vertically.
The vertical filtering results in a smooth high quality
video playback. Also by displaying both fields one af-
ter another, any motion artifacts often found in dein-
terlaced video output are removed, because the pix-
els in each field are displayed in the order in which the
original source was captured.
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