RIVA128ZX Datasheet, PDF (52/85 Pages) STMicroelectronics – 128-BIT 3D MULTIMEDIA ACCELERATOR

RIVA128ZX
128-BIT 3D MULTIMEDIA ACCELERATOR
8.5 VBI HANDLING IN THE VIDEO PORT
RIVA128ZX supports two basic modes for VBI
data capture. VBI mode 1 is for use with the Philips
SAA7111A digitizer, VBI mode 2 is for use with the
Samsung KS0127 digitizer.
In VBI mode 1, the region to be captured as VBI
data is set up in the SAA7111A via the serial inter-
face, and in the RIVA128ZX under software con-
trol. The SAA7111A responds by suppressing
generation of SAV and EAV codes for the lines se-
lected, and sending raw sample data to the port.
The RIVA128ZX Video Port capture engine starts
capturing VBI data at an EAV code in the line last
active and continues to capture data without a
break until it detects the next SAV code. VBI cap-
ture is then complete for that field.
In VBI mode 2, the region to be captured as VBI
data is set up in a similar manner. The KS0127 re-
sponds by enabling VBI data collection only during
the lines specified and framed by normal ITU-R-
656 SAV/EAV codes. The RIVA128ZX Video Port
capture engine starts capturing data at an SAV
code controlled by the device driver, and contin-
ues capturing data under control of SAV/EAV
codes until a specific EAV code identified by the
device driver is sampled. VBI capture is then com-
plete for that field. The number of bytes collected
will vary depending on the setup of the KS0127.
8.6 SCALING IN THE VIDEO PORT
The RIVA128ZX Video Port allows any arbitrary
scale factor between 1 and 31. For best results the
scale factors of 1, 2, 3, 4, 6, 8, 12, 16, and 24 are
selected to avoid filtering losses. The Video Port
decimates in the y-direction, dropping lines every
few lines depending on the vertical scaling factor.
The intention is to support filtered downscaling in
the attached video decoder.
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