User Manual - TRS-RenTelco

Option VGA Detailed Measurement Information
Back porch is the portion of the video signal that lies between the trailing edge
of the horizontal 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 of the surrounding bezel on
overscan type monitors. The duration of the left border or the right border in the
active video constitute one-tenth of the total time.
Addressable video 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 H Timing measurement is Black White Black
(required to test for compliance with the VESA Test procedure), which is located
on the Test Signal Files CD-ROM.
The Black White Black test signal contains a black pattern (10%) followed by a
white pattern (80%), and this is again followed by a black pattern (10%).
Because some graphics cards insert a border around the picture, this test signal
facilitates border detection.
If you plan to take only H Timing measurements, use a Black White 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 -BlackWhiteBlackBars.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 H Timing Results must match the values specified by the standards
depending on the timing standard selected.
How Results are
Calculated
In H Timing, if any borders are detected, their width is measured. A border is
considered present if there are pulses around SAV or EAV with heights of at least
15% of the white level. Edges of the white band are detected and addressable
video width is estimated by considering the white band is 80% of the addressable
portion of the H sync pulse width. Sync period is measured by detecting the
edges in the sync signal.
VM5000 Automatic Video Measurement Set User Manual 3-47