FS401 Datasheet, PDF (78/104 Pages) List of Unclassifed Manufacturers – PC to TV Video Scan Converters

FS401, FS403
PRODUCT SPECIFICATION
REV. NO. 1.7
5.1.6 Digital RGB Multiplexer
The EXADSEL pin in conjunction with BIPGEN in the CRE register controls a triple 24-bit multiplexer that
selects the source of RGB data to be supplied to the digital gain block. 24-bit RGB data can be accepted
from:
• TTL compatible RGB input port
• A/D converter outputs
• BiPGen, the internal test pattern generator
5.1.7 RGB Gain
Following each A/D converter is a digital gain stage that allows the A/D converter to accommodate either
700 mV or 1000 mV RGB input video signals. Gain is set by the RGBGAIN bit of the Command Register.
When using RGBGAIN, V_ADCREF should be set to 1000 mV.
5.1.8 RGB/YUV Matrix
Pixels are converted from the 24-bit RGB format to the 24-bit YUV format by an RGB/YUV matrix. UV
data is filtered and decimated prior to realignment with Y data forming a 16-bit YUV422 data stream.
5.1.9 Vertical Scaler
16-bit YUV422 data from the Transcoder is passed to the Vertical Scaler that operates on columns of
pixels. Programming the VSC registers sets vertical scale factor. VSC is the Vertical Scale Coefficient, n
which determines the vertical scaling factor:
Vertical Scaling = (1 – VSC/256)
n is the reduction (caused by the scaling filter), modulo 256, in the number incoming vertical lines. With a
range: 0 ≤ n ≤ 192; 1 ≤ VSC ≤ 1/4.
5.1.10 Flicker Filter
The FS400 flicker filter includes a variable vertical filter response in addition to a sharpness function.
The vertical averaging part of the filter is decomposed into an impulse function (no filtering) and a vertical
flicker function. Adjusting the FLK Coefficient modifies the vertical filter from no filtering (FLK = 0) to a
Three Line Average (FLK = 21), giving the user a wide choice in filtering options. A value of 16 provides
the normal 3 line flicker filter response of ¼, ½, and ¼.
In addition to the variable vertical settings, the FS400 flicker filter has a sharpness function. This function
is a two dimensional peaking function with accentuates the joint high vertical - high horizontal spatial
frequencies.
The three line variable two dimensional flicker filter is formed by summing the unit impulse function with a
vertical flicker function scaled by FLK (Flicker Coefficient) and the peaking function which is scaled by
SHP (Sharpness Coefficient). The FLK and SHP variables have 5 bits of resolutions, with a usable a
range from 0 to 21/32 for FLK, and 0 to 31/32 for SHP.
The perception of flicker varies with the angle of the flicker source to the horizontal. Experimentally it was
determined that the perceived flicker threshold was between 20 and 35 degrees. Above 35 degrees few
viewers can notice a line flicker and below 20 degrees most viewers can.
The vertical response of the flicker filter varies with the angle from horizontal and only modifies parts of
the video input that contain flicker. The plot of the filter response is shown below at 0, 14, 27, and 45
degrees from horizontal.
JANUARY 24, 2007
78
COPYRIGHT © 1999 FOCUS ENHANCEMENTS, INC.