User Manual - TRS-RenTelco

Option VGA Detailed Measurement Information
V Timing Measurement
V Timing consists of the measurements: the vertical sync pulse, the back porch,
the addressable lines, the front porch, top border, and bottom border.
Back porch is the portion of the video signal that lies between the trailing edge
of the vertical sync pulse and the start of the active picture.
Border is the period during which a background colored border is displayed in
order to allow the image to extend beyond the limits.
Addressable Lines is the period during which active video image information is
transmitted.
Front porch is the portion of the video signal between the end of the active
picture and the leading edge of the horizontal sync.
Sync pulse width is the period of the active sync pulse.
Signal Source
The test signal used for the V Timing measurement is Half White & Half Black
Bars (required to test for compliance with the VESA Test procedure), which is
located on the Test Signal Files CD-ROM.
The Half White & Half Black bars test signal contains a white bar and a black
bar.
If you plan to take only V Timing measurements, use the Half White & Half
Black Full Field test pattern. Select the bitmap file that matches the format and
the refresh rate of the test. For example, use the 640x480 -HalfWhiteHalf-
Black.bmp file to test a 640x480 resolution format.
You can also use a Matrix signal as a test signal. For more information on the
Matrix signal, refer to page 2 -16. For example, use the 640x480 -Matrix.bmp
file to test a 640x480 resolution format.
Interpreting Results
The V Timing Results must match the values specified by the timing standard
selected.
How Results are
Calculated
The V Timing measurement requires a test pattern with lines that are half white
and half black. The first and the last addressable lines are required to be in this
pattern and they indicate the beginning and end of the addressable video. If any
non-black lines are detected before the beginning of the addressable video or
after the end of it, they are considered part of the top or bottom border respectively.
Beginning five lines before the first addressable line (as per the standard), 15
lines are scanned to detect the first addressable line. With the start of addressable
video, the scan begins again at five lines before the nominal end of the address-
VM5000 Automatic Video Measurement Set User Manual 3-55